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Présenter le rendu final sur une page Instagram a comme objectif premier d'humaniser le virus créé, mais aussi de démontrer sa versatilité. En l'introduisant dans plusieurs scènes de différentes villes à travers le monde, cela renvoie à la mondialisation facile d'un virus en général.

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Bien que je ne voulais pas au départ entrer dans le thème de la Covid-19, mon projet prenait de plus en plus une tangente difficilement détachable de ce sujet.
Après réflexion et en considérant les nouveaux développements de la pandémie, j'ai opté pour un message du genre « vivre au quotidien avec un (des) virus». Sans nécessairement nommer la Covid-19 directement, mon projet présente un virus dans plusieurs situations plutôt banales du quotidien. J'en ai créer une forme de personnage - évoluant au sein d'une famille comme un membre accepté de celle-ci.

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Après plusieurs recherches sur les «bonnes» bactéries, j'en suis venue à la conclusion qu'elles sont malheureusement très laides (esthétiquement)...!
J'ai donc décidé de modéliser en 3D grâce à Blender un virus, puisqu'ils sont physiquement plus versatiles et dynamiques.
Une fois le virus créé, j'ai été en mesure de l'introduire dans l'application Adobe Aero - application de réalité augmentée
(https://www.adobe.com/ca/products/aero.html) - pour faire des tests dans mon environnement quotidien.

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How Bacteria-Eating Bacteria Could Help Win the War Against Germs (Published 2020)

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While microscopic and little known, predatory bacteria are among the world’s fiercest and most effective hunters.

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Both inside and out, our bodies harbour a huge array of micro-organisms. While bacteria are the biggest players, we also host single-celled organisms known as archaea, as well as fungi, viruses and other microbes - including viruses that attack bacteria. Together these are dubbed the human microbiota. Your body's microbiome is all the genes your microbiota contains, however colloquially the two terms are often used interchangeably.

Hang on, aren't microbes supposed to be dangerous?
It's a bit of a spectrum: some are pathogens, but others only become harmful if they get in the wrong place or boom in number, and some are very useful to the body - such as by helping to break down the array of sugars found in human breast milk. "These sugars are not broken down by the infant," said Prof John Cryan, a neuropharmacologist and microbiome expert from University College Cork. Instead, microbes in the baby's gut do the job.

Other key roles of our microbes include programming the immune system, providing nutrients for our cells and preventing colonisation by harmful bacteria and viruses.
Where do my gut microbes come from? Do I just pick them up from my surroundings?
Partly. But it is more complicated than that. "It is still a little bit controversial but for the most part it is thought that we are sterile when we are in utero, and as we are being born, as we emerge through the birth canal from our mums, we get this handover bacteria," said Cryan. "It is like a gulp at birth. Those bacteria are really important for starting the whole process."

Cryan notes that during pregnancy a mother's microbiome shifts, apparently to an optimum mix for offspring. "If you are not born by vaginal delivery, but are born by [caesarean] section, things start off being different," he said. Indeed, studies have suggested that these differences could be one of the reasons why babies born by caesarean section have a higher risk of conditions including asthma and type 1 diabetes. That said, doctors have cautioned parents against attempting to seed babies born by caesarean section with vaginal bacteria.

Our gut microbiome changes quickly over our first year or two, shaped by microbes in breast milk, the environment and other factors, and stabilises by the time we are about three years old. But our environment, our long-term diet, stress and the drugs we take, such as antibiotics, continue to play a role as we age, meaning our microbiome can change throughout our life.
It seems like microbes are everywhere - how many are we talking about?
The figure that has been bandied out since the 1970s is that microbes outnumber our own cells by about 10 to one. But a study from 2016 suggests that in fact microbial cells and human cells coexist in somewhere around a 1.3 to one ratio - suggesting they only slightly outnumber our own cells, although that doesn't count viruses and viral particles.
Does this mean I am not human?
Some say we should be seen as a , a term that reflects the intimate, co-dependent relationship humans have with microbes. "I tell this joke that the next time someone goes to the bathroom and they get rid of some of their microbes they are becoming more human," said Cryan.

But Ellen Clarke, a philosopher of biology at the University of Leeds, is not convinced. "It all depends on what you mean by 'human' in the first place," she said. "If you think that a human is a collection of cells that all share copies of the same chromosomes, then it is shocking to be told that our bodies contain cells with bacterial DNA."

But as Clarke points out, human cells don't just contain chromosomes, but also carry DNA within our cellular powerhouses, mitochondria, which are evolutionary descendants of bacteria. Our genome also contains stretches of genetic material called transposons that, at least in some cases, are thought to have been introduced long ago by viruses. "I prefer to define a human in evolutionary terms, and if we do this then mitochondria are parts of a human, and so are transposons, but gut microbes are not, and neither are prosthetic limbs nor unborn foetuses," said Clarke, pointing out that microbes can escape the body and live without us.

Are microbes the same in my gut as on my skin?

No, different parts of the body - the skin, vagina, gut - all have very different, distinct communities of microbes. While gut microbes have gained a lot of attention, microbes elsewhere are also important: in recent studies, scientists have found that bacteria commonly found on the skin might help to protect against skin cancer.

Microbiomes also differ from person to person. "When you look at the overall active microbiomes between two healthy people, even if they are living in the same city, you see a tremendous amount of disagreement in their microbiome," said Rob Knight, professor of paediatrics, computer science and engineering at the University of California San Diego and an expert on the human microbiome.
Why has the microbiome become such a hot topic for research?

Variability in the gut microbiome, Knight notes, helps to explain why people respond differently to the same foods. "Whether tomatoes are good or bad for you, whether rice is good for you or worse for you than ice cream and so on is explained by your microbiome," he said.

Over recent years the gut microbiome in particular has been linked to a plethora of diseases and conditions, from diabetes to autism and anxiety to obesity.
Why do we think the microbiome is linked to all these conditions?

The gut microbiome has also been linked to how individuals respond to certain drugs, including how cancer patients respond to chemotherapy, and it has even, tentatively, been suggested that it could be linked with how well we sleep.

Meanwhile, a range of studies have raised the importance of other aspects of our microbiome, including that the vaginal microbiome is important in whether an HIV-prevention drug applied to the vagina is effective.

While some links have come from comparing the microbiomes of different groups of people, such as those with a particular disease compared with healthy individuals, a big player in microbiome research is the germ-free mouse.

This organism is raised in a sterile environment and can then be exposed to particular microbes, or groups of microbes, to explore their impact. Such studies have been key in raising possible links between the gut microbiome and numerous aspects of our health, including mood and obesity.

Is it that particular microbes are important, or is it about the microbial community as a whole?

So might microbes be affecting our weight, or even our brains? That sounds a bit sci-fi.
With the microbiome linked to so many conditions, does tinkering with it promise a whole range of new treatments?

This is the knotty issue. In some experiments, particular strains of bacteria have been linked to particular effects or conditions, while others have shown that the diversity of the microbiome, or relative abundances of species, is important.

"It is a bit like a rainforest: you might have a very nice fern that is very happy but if that is the only thing in your rainforest and you don't have a diversity it is not going to be good [for the] soil," said Tim Spector, professor of genetic epidemiology at King's College London and author of The Diet Myth. When it comes to the microbiome, "it's having the right community of bacteria that are working together and together producing the right chemicals for your body."

When it comes to obesity, there are several ways gut microbes might influence matters, including through appetite, production of gases, efficiency of using food, and impact on the immune system and inflammation.
Does any of this actually affect patients?
When it comes to affecting mood, there are also several mechanisms. One is via the vagus nerve, a two-way highway that runs from our brain to various organs in the body, including the gut.

It is worth being cautious: many studies show associations rather than cause and effect, and some are based only on studies in germ-free mice and have not been explored in humans. Even in mice things aren't straightforward - effects are not always the same for both sexes and can differ for different strains of mice.

And there are other factors to consider: "For obesity what it looks like is in different human populations, different kinds of microbes are involved in the differences between lean and obese humans," said Knight.
Let's cut to the chase: what can I do to keep my microbiome in good shape?

Spector said: "I think everyone is right to be sceptical, and a lot of the links may just be that [microbes] are not necessarily the cause of [a disease], but they might be a secondary effect of it."

Others say it isn't surprising that our microbiome might be closely linked to our health. "All of human development and all the systems in the body have all evolved, or co-evolved, with our microbes," said Cryan. "As humans we are very much human-focused and we feel that human cells and genes have primacy, but the microbes were there first."

Up to a point. The field has already led to advances in the treatment of C difficile - an infection that causes serious diarrhoea and can prove deadly. Patients can now receive faecal transplants from a donor with a healthy microbiome to "reset" their inner community - a procedure that has been shown to rapidly cure the condition.

Some researchers, including Cryan, believe microbiome research could lead to the development of new mental health therapies. "We have coined the term 'psychobiotic' [by which we mean] a targeted intervention of the microbiome for brain health," he said.
Further reading: I Contain Multitudes, by Ed Yong Gut: The Inside Story of Our Body's Most Underrated Organ, by Giulia Enders The Psychobiotic Revolution, by Scott C Anderson with John Cryan and Ted Dinan Follow Your Gut: How the Ecosystem in Your Gut Determines Your Health, Mood, and More, by Rob Knight
While that may be some way off, Cryan believes it will become routine for doctors to keep an eye on the makeup of patients' microbiomes. "I think personally that bacteria- or microbiome-derived medicine is the future of precision medicine," he said.

This is where prebiotics and probiotics come in: the former are substances, such as the fibre inulin, on which useful microbes can thrive, while the latter are microbes themselves that are thought to be beneficial for health, such as the Lactobacillus and Bifidobacterium species.

While both prebiotics and probiotics can be taken as supplements, whether you should shell out for them is another matter: there is little advice on which prebiotics or probiotics people should consume for a particular situation, and when it comes to probiotics it isn't a dead cert that the microbes will colonise your gut when they get there, or if they will offer benefits to already healthy people, such as preventing diseases. That said, if you are taking antibiotics or have IBS, there is some evidence probiotics might be a good idea.

"It is not clear yet whether you're better off just having lots of yoghurt and other fermented foods or actually taking these formulations," said Spector, adding that in general he recommends opting for tweaking your diet to get a dose of probiotics, since it isn't clear which strains individuals should take. The same goes for prebiotics: "there is more variety in food in terms of the fibre, therefore more variety in the microbes," he said. "Ideally you combine a prebiotic and a probiotic: something like sauerkraut or kimchi."

What next?

The spotlight is on unpicking the mechanisms by which microbes are linked to human health. Among the conundrums is how and why the different strains of bacteria have different effects, while researchers are also developing studies to explore how the microbiome influences our response to food, and how different diets can tweak the microbiome. There is also a need to take more of the exciting findings from mouse studies and probe them in humans, preferably through randomised control trials.

Illustrations: Pete Gamlen

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The human microbiome: why our microbes could be key to our health

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Both inside and out, our bodies harbour a huge array of micro-organisms. While bacteria are the biggest players, we also host single-celled organisms known as archaea, as well as fungi, viruses and other microbes - including viruses that attack bacteria. Together these are dubbed the human microbiota.

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Introduction

Human activities and their effects on the climate and environment cause unprecedented animal and plant extinctions, cause loss in biodiversity and endanger animal and plant life on Earth5. Losses of species, communities and habitats are comparatively well researched, documented and publicized6. By contrast, microorganisms are generally not discussed in the context of climate change (particularly the effect of climate change on microorganisms). While invisible to the naked eye and thus somewhat intangible7, the abundance (~10 ³⁰ total bacteria and archaea)8 and diversity of microorganisms underlie their role in maintaining a healthy global ecosystem: simply put, the microbial world constitutes the life support system of the biosphere. Although human effects on microorganisms are less obvious and certainly less characterized, a major concern is that changes in microbial biodiversity and activities will affect the resilience of all other organisms and hence their ability to respond to climate change9.

Microorganisms have key roles in carbon and nutrient cycling, animal (including human) and plant health, agriculture and the global food web. Microorganisms live in all environments on Earth that are occupied by macroscopic organisms, and they are the sole life forms in other environments, such as the deep subsurface and 'extreme' environments. Microorganisms date back to the origin of life on Earth at least 3.8 billion years ago, and they will likely exist well beyond any future extinction events.

Although microorganisms are crucial in regulating climate change, they are rarely the focus of climate change studies and are not considered in policy development. Their immense diversity and varied responses to environmental change make determining their role in the ecosystem challenging. In this Consensus Statement, we illustrate the links between microorganisms, macroscopic organisms and climate change, and put humanity on notice that the microscopic majority can no longer be the unseen elephant in the room. Unless we appreciate the importance of microbial processes, we fundamentally limit our understanding of Earth's biosphere and response to climate change and thus jeopardize efforts to create an environmentally sustainable future6 (Box 1).

Box 1 Scientists' warning

Scope of the Consensus Statement

In this Consensus Statement, we address the effects of microorganisms on climate change, including microbial climate-active processes and their drivers. We also address the effects of climate change on microorganisms, focusing on the influences of climate change on microbial community composition and function, physiological responses and evolutionary adaptation. Although we focus on microorganism-climate connections, human activities with a less direct but possibly synergistic effect, such as via local pollution or eutrophication, are also addressed.

For the purpose of this Consensus Statement, we define 'microorganism' as any microscopic organism or virus not visible to the naked eye (smaller than 50 μm) that can exist in a unicellular, multicellular (for example, differentiating species), aggregate (for example, biofilm) or viral form. In addition to microscopic bacteria, archaea, eukaryotes and viruses, we discuss certain macroscopic unicellular eukaryotes (for example, larger marine phytoplankton) and wood-decomposing fungi. Our intent is not to exhaustively cover all environments nor all anthropogenic influences but to provide examples from major global biomes (marine and terrestrial) that highlight the effects of climate change on microbial processes and the consequences. We also highlight agriculture and infectious diseases and the role of microorganisms in climate change mitigation. Our Consensus Statement alerts microbiologists and non-microbiologists to address the roles of microorganisms in accelerating or mitigating the impacts of anthropogenic climate change (Box 1).

Marine biome

Marine biomes cover ~70% of Earth's surface and range from coastal estuaries, mangroves and coral reefs to the open oceans (Fig. 1). Phototrophic microorganisms use the sun's energy in the top 200 m of the water column, whereas marine life in deeper zones uses organic and inorganic chemicals for energy10. In addition to sunlight, the availability of other energy forms and water temperature (ranging from approximately −2 °C in ice-covered seas to more than 100 °C in hydrothermal vents) influence the composition of marine communities11. Rising temperatures not only affect biological processes but also reduce water density and thereby stratification and circulation, which affect organismal dispersal and nutrient transport. Precipitation, salinity and winds also affect stratification, mixing and circulation. Nutrient inputs from air, river and estuarine flows also affect microbial community composition and function, and climate change affects all these physical factors.

In marine environments, microbial primary production contributes substantially to CO ₂ sequestration. Marine microorganisms also recycle nutrients for use in the marine food web and in the process release CO ₂ to the atmosphere. In a broad range of terrestrial environments, microorganisms are the key decomposers of organic matter and release nutrients in the soil for plant growth as well as CO ₂ and CH ₄ into the atmosphere. Microbial biomass and other organic matter (remnants of plants and animals) are converted to fossil fuels over millions of years. By contrast, burning of fossil fuels liberates greenhouse gases in a small fraction of that time. As a result, the carbon cycle is extremely out of balance, and atmospheric CO ₂ levels will continue to rise as long as fossil fuels continue to be burnt. The many effects of human activities, including agriculture, industry, transport, population growth and human consumption, combined with local environmental factors, including soil type and light, greatly influence the complex network of microbial interactions that occur with other microorganisms, plants and animals. These interactions dictate how microorganisms respond to and affect climate change (for example, through greenhouse gas emissions) and how climate change (for example, higher CO ₂ levels, warming, and precipitation changes) in turn affect microbial responses. OMZ, oxygen minimum zone.

The overall relevance of microorganisms to ocean ecosystems can be appreciated from their number and biomass in the water column and subsurface: the total number of cells is more than 10 ²⁹ (refs) and the Census of Marine Life estimates that 90% of marine biomass is microbial. Beyond their sheer numbers, marine microorganisms fulfil key ecosystem functions. By fixing carbon and nitrogen, and remineralizing organic matter, marine microorganisms form the basis of ocean food webs and thus global carbon and nutrient cycles13. The sinking, deposition and burial of fixed carbon in particulate organic matter to marine sediments is a key, long-term mechanism for sequestering CO ₂ from the atmosphere. Therefore, the balance between regeneration of CO ₂ and nutrients via remineralization versus burial in the seabed determines the effect on climate change.

In addition to getting warmer (from increased atmospheric CO ₂ concentrations enhancing the greenhouse effect), oceans have acidified by ~0.1 pH units since preindustrial times, with further reductions of 0.3-0.4 units predicted by the end of the century. Given the unprecedented rate of pH change, there is a need to rapidly learn how marine life will respond22. The impact of elevated greenhouse gas concentrations on ocean temperature, acidification, stratification, mixing, thermohaline circulation, nutrient supply, irradiation and extreme weather events affects the marine microbiota in ways that have substantial environmental consequences, including major shifts in productivity, marine food webs, carbon export and burial in the seabed19,23,24,25,26,27,28,29.

Microorganisms affect climate change

Marine phytoplankton perform half of the global photosynthetic CO ₂ fixation (net global primary production of ~50 Pg C per year) and half of the oxygen production despite amounting to only ~1% of global plant biomass30. In comparison with terrestrial plants, marine phytoplankton are distributed over a larger surface area, are exposed to less seasonal variation and have markedly faster turnover rates than trees (days versus decades)30. Therefore, phytoplankton respond rapidly on a global scale to climate variations. These characteristics are important when one is evaluating the contributions of phytoplankton to carbon fixation and forecasting how this production may change in response to perturbations. Predicting the effects of climate change on primary productivity is complicated by phytoplankton bloom cycles that are affected by both bottom-up control (for example, availability of essential nutrients and vertical mixing) and top-down control (for example, grazing and viruses). Increases in solar radiation, temperature and freshwater inputs to surface waters strengthen ocean stratification and consequently reduce transport of nutrients from deep water to surface waters, which reduces primary productivity. Conversely, rising CO ₂ levels can increase phytoplankton primary production, but only when nutrients are not limiting.

Some studies indicate that overall global oceanic phytoplankton density has decreased in the past century39, but these conclusions have been questioned because of the limited availability of long-term phytoplankton data, methodological differences in data generation and the large annual and decadal variability in phytoplankton production. Moreover, other studies suggest a global increase in oceanic phytoplankton production44 and changes in specific regions or specific phytoplankton groups45,46. The global sea ice ( Sea Ice Index) is declining, leading to higher light penetration and potentially more primary production47; however, there are conflicting predictions for the effects of variable mixing patterns and changes in nutrient supply and for productivity trends in polar zones34. This highlights the need to collect long-term data on phytoplankton production and microbial community composition. Long-term data are needed to reliably predict how microbial functions and feedback mechanisms will respond to climate change, yet only very few such datasets exist (for example, the Hawaii Ocean Time-series and the Bermuda Atlantic Time-series Study). In this context, the Global Ocean Sampling Expedition51, transects of the Southern Ocean52,53, and the Tara Oceans Consortium11,54,55,56,57,58,59 provide metagenome data that are a valuable baseline of marine microorganisms.

Diatoms perform 25-45% of total primary production in the oceans, owing to their prevalence in open-ocean regions when total phytoplankton biomass is maximal63. Diatoms have relatively high sinking speeds compared with other phytoplankton groups, and they account for ~40% of particulate carbon export to depth62,64. Physically driven seasonal enrichments in surface nutrients favour diatom blooms. Anthropogenic climate change will directly affect these seasonal cycles, changing the timing of blooms and diminishing their biomass, which will reduce primary production and CO ₂ uptake65. Remote sensing data suggest a global decline of diatoms between 1998 and 2012, particularly in the North Pacific, which is associated with shallowing of the surface mixed layer and lower nutrient concentrations46.

In addition to the contribution of marine phytoplankton to CO ₂ sequestration, chemolithoautotrophic archaea and bacteria fix CO ₂ under dark conditions in deep ocean waters69 and at the surface during polar winter70. Marine bacteria and archaea also contribute substantially to surface ocean respiration and cycling of many elements18. Seafloor methanogens and methanotrophs are important producers and consumers of CH ₄, but their influence on the atmospheric flux of this greenhouse gas is uncertain71. Marine viruses, bacteriovorous bacteria and eukaryotic grazers are also important components of microbial food webs; for example, marine viruses influence how effectively carbon is sequestered and deposited into the deep ocean57. Climate change affects predator-prey interactions, including virus-host interactions, and thereby global biogeochemical cycles72.

Oxygen minimum zones (OMZs) have expanded in the past 50 years as a result of ocean warming, which reduces oxygen solubility. OMZs are global sinks for reactive nitrogen, and microbial production of N ₂ and N ₂ O accounts for ~25-50% of nitrogen loss from the ocean to the atmosphere. Furthermore, OMZs are the largest pelagic methane reservoirs in the ocean and contribute substantially to open ocean methane cycling. The observed and predicted future expansion of OMZs may therefore considerably affect ocean nutrient and greenhouse gas budgets, and the distributions of oxygen-dependent organisms.

The top 50 cm of deep-sea sediments contains ~1 × 10 ²⁹ microorganisms8,16, and the total abundances of archaea and bacteria in these sediments increase with latitude (from 34° N to 79° N) with specific taxa (such as Marine Group I Thaumarchaeota) contributing disproportionately to the increase76. Benthic microorganisms show biogeographic patterns and respond to variations in the quantity and quality of the particulate matter sinking to the seafloor77. As a result, climate change is expected to particularly affect the functional processes that deep-sea benthic archaea perform (such as ammonia oxidation) and associated biogeochemical cycles76.

Aerosols affect cloud formation, thereby influencing sunlight irradiation and precipitation, but the extent to which and the manner in which they influence climate remains uncertain78. Marine aerosols consist of a complex mixture of sea salt, non-sea-salt sulfate and organic molecules and can function as nuclei for cloud condensation, influencing the radiation balance and, hence, climate79,80. For example, biogenic aerosols in remote marine environments (for example, the Southern Ocean) can increase the number and size of cloud droplets, having similar effects on climate as aerosols in highly polluted regions. Specifically, phytoplankton emit dimethylsulfide, and its derivate sulfate promotes cloud condensation79,84. Understanding the ways in which marine phytoplankton contribute to aerosols will allow better predictions of how changing ocean conditions will affect clouds and feed back on climate84. In addition, the atmosphere itself contains ~10 ²² microbial cells, and determining the ability of atmospheric microorganisms to grow and form aggregates will be valuable for assessing their influence on climate8.

Vegetated coastal habitats are important for carbon sequestration, determined by the full trophic spectrum from predators to herbivores, to plants and their associated microbial communities85. Human activity, including anthropogenic climate change, has reduced these habitats over the past 50 years by 25-50%, and the abundance of marine predators has dropped by up to 90%. Given such extensive perturbation, the effects on microbial communities need to be evaluated because microbial activity determines how much carbon is remineralized and released as CO ₂ and CH ₄.

Climate change affects microorganisms

Climate change perturbs interactions between species and forces species to adapt, migrate and be replaced by others or go extinct28,88. Ocean warming, acidification, eutrophication and overuse (for example, fishing, tourism) together cause the decline of coral reefs and may cause ecosystems shifts towards macroalgae and benthic cyanobacterial mats94,95. The capacity for corals to adapt to climate change is strongly influenced by the responses of their associated microorganisms, including microalgal symbionts and bacteria. The hundreds to thousands of microbial species that live on corals are crucial for host health, for example by recycling the waste products, by provisioning essential nutrients and vitamins and by assisting the immune system to fight pathogens99. However, environmental perturbation or coral bleaching can change the coral microbiome rapidly. Such shifts undoubtedly influence the ecological functions and stability of the coral-microorganism system, potentially affecting the capacity and pace at which corals adapt to climate change, and the relationships between corals and other components of the reef ecosystem99,100.

Generally, microorganisms can disperse more easily than macroscopic organisms. Nevertheless, biogeographic distinctions occur for many microbial species, with dispersal, lifestyle (for example, host association) and environmental factors strongly influencing community composition and function. Ocean currents and thermal and latitudinal gradients are particularly important for marine communities104,105. If movement to more favourable environments is impossible, evolutionary change may be the only survival mechanism88. Microorganisms, such as bacteria, archaea and microalgae, with large population sizes and rapid asexual generation times have high adaptive potential22. Relatively few studies have examined evolutionary adaptation to ocean acidification or other climate change-relevant environmental variables22,28. Similarly, there is limited understanding of the molecular mechanisms of physiological responses and the implications of those responses for biogeochemical cycles18.

However, several studies have demonstrated effects of elevated CO ₂ levels on individual phytoplankton species, which may disrupt broader ecosystem-level processes. A field experiment demonstrated that increasing CO ₂ levels provide a selective advantage to a toxic microalga, Vicicitus globosus, leading to disruption of organic matter transfer across trophic levels106. The marine cyanobacterial genus Trichodesmium responds to long-term (4.5-year) exposure to elevated CO ₂ levels with irreversible genetic changes that increase nitrogen fixation and growth107. For the photosynthetic green alga Ostreococcus tauri, elevated CO ₂ levels increase growth, cell size and carbon-to-nitrogen ratios108. Higher CO ₂ levels also affect the population structure of O. tauri, with changes in ecotypes and niche occupation, thereby affecting the broader food webs and biogeochemical cycles108. Rather than producing larger cells, the calcifying phytoplankton species Emiliania huxleyi responds to the combined effects of elevated temperature and elevated CO ₂ levels (and associated acidification) by producing smaller cells that contain less carbon109. However, for this species, overall production rates do not change as a result of evolutionary adaptation to higher CO ₂ levels109. Responses to CO ₂ levels differ between communities (for example, between Arctic phytoplankton and Antarctic phytoplankton110). A mesocosm study identified variable changes in the diversity of viruses that infect E. huxleyi when it is growing under elevated CO ₂ levels, and noted the need to determine whether elevated CO ₂ levels directly affected viruses, hosts or the interactions between them111. These examples illustrate the need to improve our understanding of evolutionary processes and incorporate that knowledge into predictions of the effects of climate change.

Ocean acidification presents marine microorganisms with pH conditions well outside their recent historical range, which affects their intracellular pH homeostasis18,112. Species that are less adept at regulating internal pH will be more affected, and factors such as organism size, aggregation state, metabolic activity and growth rate influence the capacity for regulation112.

Lower pH causes bacteria and archaea to change gene expression in ways that support cell maintenance rather than growth18. In mesocosms with low phytoplankton biomass, bacteria committed more resources to pH homeostasis than bacteria in nutrient-enriched mesocosms with high phytoplankton biomass. Consequently, ocean acidification is predicted to alter the microbial food web via changes in cellular growth efficiency, carbon cycling and energy fluxes, with the biggest effects expected in the oligotrophic regions, which include most of the ocean18. Experimental comparisons of Synechococcus sp. growth under both present and predicted future pH concentrations showed effects not only on the cyanobacteria but also on the cyanophage viruses that infect them113.

Environmental temperature and latitude correlate with the diversity, distribution and/or temperature optimum ( T opt) of certain marine taxa, with models predicting that rising temperatures will cause a poleward shift of cold-adapted communities. However, T opt of phytoplankton from polar and temperate waters was found to be substantially higher than environmental temperatures, and an eco-evolutionary model predicted that T opt for tropical phytoplankton would be substantially higher than observed experimental values116. Understanding how well microorganisms are adapted to environmental temperature and predicting how they will respond to warming requires assessments of more than T opt, which is generally a poor indicator of physiological and ecological adaptation of microorganisms from cold environments119.

Many environmental and physiological factors influence the responses and overall competitiveness of microorganisms in their native environment. For example, elevated temperatures increase protein synthesis in eukaryotic phytoplankton while reducing cellular ribosome concentration120. As the biomass of eukaryotic phytoplankton is ~1 Gt C (ref.13) and ribosomes are phosphate rich, climate change-driven alteration of their nitrogen-to-phosphate ratio will affect resource allocation in the global ocean120. Ocean warming is thought to favour smaller plankton types over larger ones, changing biogeochemical fluxes such as particle export121. Increased ocean temperatures, acidification and decreased nutrient supplies are projected to increase the extracellular release of dissolved organic matter from phytoplankton, with changes in the microbial loop possibly causing increased microbial production at the expense of higher trophic levels122. Warming can also alleviate iron limitation of nitrogen-fixing cyanobacteria, with potentially profound implications for new nitrogen supplied to food webs of the future warming oceans123. Careful attention needs to be paid to how to quantify and interpret responses of environmental microorganisms to ecosystem changes and stresses linked to climate change124,125. Key questions thus remain about the functional consequences of community shifts, such as changes in carbon remineralization versus carbon sequestration, and nutrient cycling.

Terrestrial biome

There is ~100-fold more terrestrial biomass than marine biomass, and terrestrial plants account for a large proportion of Earth's total biomass15. Terrestrial plants perform roughly half of net global primary production30,67. Soils store ~2,000 billion tonnes of organic carbon, which is more than the combined pool of carbon in the atmosphere and vegetation126. The total number of microorganisms in terrestrial environments is ~10 ²⁹, similar to the total number in marine environments8. Soil microorganisms regulate the amount of organic carbon stored in soil and released back to the atmosphere, and indirectly influence carbon storage in plants and soils through provision of macronutrients that regulate productivity (nitrogen and phosphorus)126,127. Plants provide a substantial amount of carbon to their mycorrhizal fungal symbionts, and in many ecosystems, mycorrhizal fungi are responsible for substantial amounts of nitrogen and phosphorus acquisition by plants128.

Plants remove CO ₂ from the atmosphere through photosynthesis and create organic matter that fuels terrestrial ecosystems. Conversely, autotrophic respiration by plants (60 Pg C per year) and heterotrophic respiration by microorganisms (60 Pg C per year) release CO ₂ back into the atmosphere126,129. Temperature influences the balance between these opposing processes and thus the capacity of the terrestrial biosphere to capture and store anthropogenic carbon emissions (currently, storing approximately one quarter of emissions) (Fig. 1). Warming is expected to accelerate carbon release into the atmosphere129.

Forests cover ~30% of the land surface, contain ~45% of terrestrial carbon, make up ~50% of terrestrial primary production and sequester up to 25% of anthropogenic CO ₂ (refs130,131). Grasslands cover ~29% of the terrestrial surface132. Non-forested, arid and semiarid regions (47%) are important for the carbon budget and respond differently to anthropogenic climate change than forested regions132,133. Lakes make up ~4% of the non-glaciated land area134, and shallow lakes emit substantial amounts of CH ₄ (refs135,136). Peat (decomposed plant litter) covers ~3% of the land surface and, due to plant productivity exceeding decomposition, intact peatlands function as a global carbon sink and contain ~30% of global soil carbon137,138. In permafrost, the accumulation of carbon in organic matter (remnants of plants, animals and microorganisms) far exceeds the respiratory losses, creating the largest terrestrial carbon sink. Climate warming of 1.5-2 °C (relative to the global mean surface temperature in 1850-1900) is predicted to reduce permafrost by 28-53% (compared with levels in 1960-1990)142, thereby making large carbon reservoirs available for microbial respiration and greenhouse gas emissions.

Evaluations of the top 10 cm of soil143 and whole-soil profiles to 100 cm deep, which contain older stocks of carbon144, demonstrate that warming increases carbon loss to the atmosphere. Explaining differences in carbon loss between different soil sites will require a greater range of predictive variables (in addition to soil organic matter content, temperature, precipitation, pH and clay content)145,146. Nevertheless, predictions from global assessments of responses to warming indicate that terrestrial carbon loss under warming is causing a positive feedback that will accelerate the rate of climate change143, particularly in cold and temperate soils, which store much of the global soil carbon147.

Microorganisms affect climate change

Higher CO ₂ levels in the atmosphere increase primary productivity and thus forest leaf and root litter, which leads to higher carbon emissions due to microbial degradation151. Higher temperatures promote higher rates of terrestrial organic matter decomposition152. The effect of temperature is not just a kinetic effect on microbial reaction rates but results from plant inputs stimulating microbial growth.

Several local environmental factors (such as microbial community composition, density of dead wood, nitrogen availability and moisture) influence rates of microbial activity (for example, fungal colonization of wood) necessitating Earth system model predictions of soil carbon losses through climate warming to incorporate local controls on ecosystem processes155. In this regard, plant nutrient availability affects the net carbon balance in forests, with nutrient-poor forests releasing more carbon than nutrient-rich forests156. Microbial respiration may be lower in nutrient-rich forests as plants provide less carbon (for example, as root exudates) to rhizosphere microorganisms157.

Plants release ~50% of fixed carbon into the soil, which is available for microbial growth. In addition to microorganisms using exudates as an energy source, exudates can disrupt mineral-organic associations, liberating organic compounds from minerals that are used for microbial respiration, thereby increasing carbon release159. The relevance of these plant-mineral interactions illustrates the importance of biotic-abiotic interactions, in addition to biotic interactions (plant-microorganism) when one is evaluating the influence of climate change159. Thermodynamic models that incorporate the interactions of microorganisms and secreted enzymes with organic matter and minerals have been used to predict soil carbon-climate feedbacks in response to increasing temperature; one study predicted more variable but weaker soil carbon-climate feedbacks from a thermodynamic model than from static models160.

The availability of soil organic matter for microbial degradation versus long-term storage depends on many environmental factors, including the soil mineral characteristics, acidity and redox state; water availability; climate; and the types of microorganisms present in the soil161. The nature of the organic matter, in particular substrate complexity, affects microbial decomposition. Furthermore, the microbial capacity to access organic matter differs between soil types (for example, with different clay content)162. If access is taken into account, increasing atmospheric CO ₂ levels are predicted to allow greater microbial decomposition and less soil retention of organic carbon162.

Elevated CO ₂ concentrations enhance competition for nitrogen between plants and microorganisms163. Herbivores (invertebrates and mammals) affect the amount of organic matter that is returned to soil and thereby microbial biomass and activity164. For example, grasshoppers diminish plant biomass and plant nitrogen demand, thereby increasing microbial activity163. Climate change can reduce herbivory, resulting in overall alterations to global nitrogen and carbon cycles that reduce terrestrial carbon sequestration163. Detritivores (for example, earthworms) influence greenhouse gas emissions by indirectly affecting plants (for example, by increasing soil fertility) and soil microorganisms165. Earthworms modify soils through feeding, burrowing and deposition of waste products. The anaerobic gut environment of earthworms harbours microorganisms that perform denitrification and produce N ₂O. Earthworms enhance soil fertility, and their presence can result in net greenhouse gas emissions165, although the combined effects of increased temperature and decreased rainfall on detritivore feeding and microbial respiration may reduce emissions166.

In peatlands, decay-resistant litter (for example, antimicrobial phenolics and polysaccharides of Sphagnum mosses) inhibits microbial decomposition, and water saturation restricts oxygen exchange and promotes the growth of anaerobes and release of CO ₂ and CH ₄ (refs137,167). Increased temperature and reduced soil water content caused by climate change promote the growth of vascular plants (ericaceous shrubs) but reduce the productivity of peat moss. Changes in plant litter composition and associated microbial processes (for example, reduced immobilization of nitrogen and enhanced heterotrophic respiration) are switching peatlands from carbon sinks to carbon sources137.

Melting and degradation of permafrost allows microbial decomposition of previously frozen carbon, releasing CO ₂ and CH ₄ (refs). Coastal permafrost erosion will lead to the mobilization of large quantities of carbon to the ocean, with potentially large CO ₂ emissions occurring through increased microbial remineralization170, causing a positive feedback loop that accelerates climate change139,140,141,168,169,170,171. Melting of permafrost leads to increases in water-saturated soils172, which promotes anaerobic CH ₄ production by methanogens and CO ₂ production by a range of microorganisms. Production is slow compared with metabolism in drained aerobic soils, which release CO ₂ rather than CH ₄. However, a 7-year laboratory study of CO ₂ and CH ₄ production found that once methanogen communities became active in thawing permafrost, equal amounts of CO ₂ and CH ₄ were formed under anoxic conditions, and it was predicted that by the end of the century, carbon emissions from anoxic environments will drive climate change to a greater extent than emissions from oxic environments172.

A 15-year mesocosm study that simulated freshwater lake environments determined that the combined effects of eutrophication and warming can lead to large increases in CH ₄ ebullition (bubbles from accumulated gas)135. As small lakes are susceptible to eutrophication and tend to be located in climate-sensitive regions, the role of lake microorganisms in contributing to global greenhouse gas emissions needs to be evaluated135,136.

Climate change affects microorganisms

Shifts in climate can influence the structure and diversity of microbial communities directly (for example, seasonality and temperature) or indirectly (for example, plant composition, plant litter and root exudates). Soil microbial diversity influences plant diversity and is important for ecosystem functions, including carbon cycling173,174.

Both short-term laboratory warming and long-term (more than 50 years) natural geothermal warming initially increased the growth and respiration of soil microorganisms, leading to net CO ₂ release and subsequent depletion of substrates, causing a decrease in biomass and reduced microbial activity175. This implies that microbial communities do not readily adapt to higher temperatures, and the resulting effects on reaction rates and substrate depletion reduce overall carbon loss175. By contrast, a 10-year study found that soil communities adapted to increased temperature by changing composition and patterns of substrate use, leading to less carbon loss than would have occurred without adaptation176. Substantial changes in bacterial and fungal communities were also found in forest soils with a more than 20 °C average annual temperature range177, and in response to warming across a 9-year study of tall-grass prairie soils178.

Two studies assessed the effects of elevated temperatures on microbial respiration rates and mechanisms and outcomes of adaptation179,180. The studies examined a wide range of environmental temperatures (−2 to 28 °C), dryland soils (110 samples) and boreal, temperate and tropical soils (22 samples), and evaluated how communities respond to three different temperatures (~10-30 °C). Thermal adaptation was linked to biophysical characteristics of cell membranes and enzymes (reflecting activity-stability trade-offs180) and the genomic potential of microorganisms (with warmer environments having microbial communities with more diverse lifestyles179). Respiration rates per unit biomass were lower in soils from higher-temperature environments, indicating that thermal adaptation of microbial communities may lessen positive climate feedbacks. However, as respiration depends on multiple interrelated factors (not just on one variable, such as temperature), such mechanistic insights into microbial physiology need to be represented in biogeochemical models of possible positive climate feedbacks.

Microbial growth responses to temperature change are complex and varied181. Microbial growth efficiency is a measure of how effectively microorganisms convert organic matter into biomass, with lower efficiency meaning more carbon is released to the atmosphere182,183. A 1-week laboratory study found that increasing temperature led to increases in microbial turnover but no change in microbial growth efficiency, and predicted that warming would promote carbon accumulation in soil183. A field study spanning 18 years found microbial efficiency was reduced at higher soil temperature, with decomposition of recalcitrant, complex substrates increasing by the end of the period along with a net loss of soil carbon182.

Similarly, in a 26-year forest-soil warming study, temporal variation occurred in organic matter decomposition and CO ₂ release184, leading to changes in microbial community composition and carbon use efficiency, reduced microbial biomass and reduced microbially accessible carbon184. Overall, the study predicted anthropogenic climate change to cause long-term, increasing and sustained carbon release184. Similar predictions arise from Earth system models that simulate microbial physiological responses185 or incorporate the effects of freezing and thawing of cold-climate soils186.

Climate change directly and indirectly influences microbial communities and their functions through several interrelated factors, such as temperature, precipitation, soil properties and plant input. As soil microorganisms in deserts are carbon limited, increased carbon input from plants promotes transformation of nitrogenous compounds, microbial biomass, diversity (for example, of fungi), enzymatic activity and use of recalcitrant organic matter133. Although these changes may enhance respiration and net loss of carbon from soil, the specific characteristics of arid and semiarid regions may mean they could function as carbon sinks133. However, a study of 19 temperate grassland sites found that seasonal differences in rainfall constrain biomass accumulation132. To better understand aboveground plant-biomass responses to CO ₂ levels and seasonal precipitation, we also need improved knowledge of microbial community responses and functions.

Metagenome data, including metagenome-assembled genomes, provide knowledge of key microbial groups that metabolize organic matter and release CO ₂ and CH ₄ and link these groups to the biogeochemistry occurring in thawing permafrost. Tundra microbial communities change in the soil layer of permafrost after warming192. Within 1.5 years of warming, the functional potential of the microbial communities changed markedly, with an increasing abundance of genes involved in aerobic and anaerobic carbon decomposition and nutrient cycling. Although microbial metabolism stimulates primary productivity by plants, the balance between microbial respiration and primary productivity results in a net release of carbon to the atmosphere192. When forests expand into warming regions of tundra, plant growth can produce a net loss of carbon, possibly as a result of root exudates stimulating microbial decomposition of native soil carbon153,193. Although there are reports of carbon accumulating owing to warming (for example, ref.183), most studies describe microbial community responses that result in carbon loss.

Rapid warming of the Antarctic Peninsula and associated islands resulted in range expansion of Antarctic hair grass ( Deschampsia antarctica), as it outcompetes other indigenous species (for example, the moss Sanionia uncinata) through the superior capacity of its roots to acquire peptides and thus nitrogen194. The ability of the grass to be competitive depends on microbial digestion of extracellular proteins and generation of amino acids, nitrate and ammonium194. As warmer soils in this region harbour greater fungal diversity, climate change is predicted to cause changes in the fungal communities that will affect nutrient cycling and primary productivity195. Cyanobacterial diversity and toxin production within benthic mats from both the Antarctic Peninsula and the Arctic increased during 6 months of exposure to high growth temperatures196. A shift to toxin-producing species or increased toxin production by existing species could affect polar freshwater lakes, where cyanobacteria are often the dominant benthic primary producers196.

Climate change is likely to increase the frequency, intensity and duration of cyanobacterial blooms in many eutrophic lakes, reservoirs and estuaries197,198. Bloom-forming cyanobacteria produce a variety of neurotoxins, hepatotoxins and dermatoxins, which can be fatal to birds and mammals (including waterfowl, cattle and dogs) and threaten the use of waters for recreation, drinking water production, agricultural irrigation and fisheries198. Toxic cyanobacteria have caused major water quality problems, for example in Lake Taihu (China), Lake Erie (USA), Lake Okeechobee (USA), Lake Victoria (Africa) and the Baltic Sea.

Climate change favours cyanobacterial blooms both directly and indirectly198. Many bloom-forming cyanobacteria can grow at relatively high temperatures201. Increased thermal stratification of lakes and reservoirs enables buoyant cyanobacteria to float upwards and form dense surface blooms, which gives them better access to light and hence a selective advantage over nonbuoyant phytoplankton organisms202,203. Protracted droughts during summer increase water residence times in reservoirs, rivers and estuaries, and these stagnant warm waters can provide ideal conditions for cyanobacterial bloom development204.

The capacity of the harmful cyanobacterial genus Microcystis to adapt to elevated CO ₂ levels was demonstrated in both laboratory and field experiments205. Microcystis spp. take up CO ₂ and HCO ₃− and accumulate inorganic carbon in carboxysomes, and strain competitiveness was found to depend on the concentration of inorganic carbon. As a result, climate change and increased CO ₂ levels are expected to affect the strain composition of cyanobacterial blooms205.

Agriculture

According to the World Bank ( World Bank data on agricultural land), nearly 40% of the terrestrial environment is devoted to agriculture. This proportion is predicted to increase, leading to substantial changes in soil cycling of carbon, nitrogen and phosphorus, among other nutrients. Furthermore, these changes are associated with a marked loss of biodiversity206, including of microorganisms207. There is increasing interest in using plant-associated and animal-associated microorganisms to increase agricultural sustainability and mitigate the effects of climate change on food production, but doing so requires a better understanding of how climate change will affect microorganisms.

Microorganisms affect climate change

Methanogens produce methane in natural and artificial anaerobic environments (sediments, water-saturated soils such as rice paddies, gastrointestinal tracts of animals (particularly ruminants), wastewater facilities and biogas facilities), in addition to the anthropogenic methane production associated with fossil fuels208 (Fig. 2). The main sinks for CH ₄ are atmospheric oxidation and microbial oxidation in soils, sediments and water208. Atmospheric CH ₄ levels have risen sharply in recent years (2014-2017) but the reasons are unclear so far, although they involve increased emissions from methanogens and/or fossil fuel industries and/or reduced atmospheric CH ₄ oxidation, thereby posing a major threat to controlling climate warming209.

Agricultural practices influence microbial communities in specific ways. Land usage (for example, plant type) and sources of pollution (for example, fertilizers) perturb microbial community composition and function, thereby altering natural cycles of carbon, nitrogen and phosphorus transformations. Methanogens produce substantial quantities of methane directly from ruminant animals (for example, cattle, sheep and goats) and saturated soils with anaerobic conditions (for example, rice paddies and constructed wetlands). Human activities that cause a reduction in microbial diversity also reduce the capacity for microorganisms to support plant growth.

Rice feeds half of the global population210, and rice paddies contribute ~20% of agricultural CH ₄ emissions despite covering only ~10% of arable land. Anthropogenic climate change is predicted to double CH ₄ emissions from rice production by the end of the century210. Ruminant animals are the largest single source of anthropogenic CH ₄ emissions, with a 19-48 times larger carbon footprint for ruminant meat production than plant-based high-protein foods211. Even the production of meat from non-ruminant animals (such as pigs, poultry and fish) produces 3-10 times more CH ₄ than high-protein plant foods211.

The combustion of fossil fuels and the use of fertilizers has greatly increased the environmental availability of nitrogen, perturbing global biogeochemical processes and threatening ecosystem sustainability212,213. Agriculture is the largest emitter of the potent greenhouse gas N ₂O, which is released by microbial oxidation and reduction of nitrogen214. The enzyme N ₂O reductase in rhizobacteria (in root nodules) and other soil microorganisms can also convert N ₂O to N ₂ (not a greenhouse gas). Climate change perturbs the rate at which microbial nitrogen transformations occur (decomposition, mineralization, nitrification, denitrification and fixation) and release N ₂O (ref.213). There is an urgent need to learn about the effects of climate change and other human activities on microbial transformations of nitrogen compounds.

Climate change affects microorganisms

Crop farming ranges from extensively managed (small inputs of labour, fertilizer and capital) to intensively managed (large inputs). Increasing temperature and drought strongly affect the ability to grow crops215. Fungal-based soil food webs are common in extensively managed farming (for example, grasslands) and are better able to adapt to drought than bacterial-based food webs, which are common in intensive systems (for example, wheat)216,217. A global assessment of topsoil found that soil fungi and bacteria occupy specific niches and respond differently to precipitation and soil pH, indicating that climate change would have differential impacts on their abundance, diversity and functions218. Aridity, which is predicted to increase owing to climate change, reduces bacterial and fungal diversity and abundance in global drylands219. Reducing soil microbial diversity reduces the overall functional potential of microbial communities, thereby limiting their capacity to support plant growth173.

The combined effects of climate change and eutrophication caused by fertilizers can have major, potentially unpredictable effects on microbial competitiveness. For example, nutrient enrichment typically favours harmful algal blooms, but a different outcome was observed in the relatively deep Lake Zurich220. Reducing phosphorus inputs from fertilizers reduced eukaryotic phytoplankton blooms but increased the nitrogen-to-phosphorus ratio and thus the non-nitrogen-fixing cyanobacterium Planktothrix rubescens became dominant220. In the absence of effective predation, annual mixing has an important role in controlling cyanobacterial populations. However, warming increased thermal stratification and reduced mixing, thereby facilitating the persistence of the toxic cyanobacteria220.

Infectious diseases

Climate change affects the occurrence and spread of diseases in marine and terrestrial biota221 (Fig. 3), depending on diverse socioeconomic, environmental and host-pathogen-specific factors222. Understanding the spread of disease and designing effective control strategies requires knowledge of the ecology of pathogens, their vectors and their hosts, and the influence of dispersal and environmental factors223 (Table 1). For example, there is a strong link between increasing sea surface temperatures and coral disease and, although the disease mechanisms are not absolutely clear for all the different syndromes, associations with microbial pathogens exist. Peaks in disease prevalence coincide with periodicities in the El Niño Southern Oscillation (ENSO)227. In particular, in some coral species, ocean warming can alter the coral microbiome, disrupting the host-symbiont equilibrium, shifting defensive mechanisms and nutrient cycling pathways that may contribute to bleaching and disease99. Ocean acidification may also directly cause tissue damage in organisms such as fish, potentially contributing to a weakened immune system that creates opportunities for bacterial invasion228.

Anthropogenic climate change stresses native life, thereby enabling pathogens to increasingly cause disease. The impact on aquaculture, food-producing animals and crops threatens global food supply. Human activities, such as population growth and transport, combined with climate change increase antibiotic resistance of pathogens and the spread of waterborne and vector-borne pathogens, thereby increasing diseases of humans, other animals and plants.

Table 1 Transmission response of pathogens to climatic and environmental factors

Sea star species declined by 80-100% along an ~3000 km section of the North American west coast, with peak declines occurring during anomalous increases in sea surface temperatures229. As sea stars are important predators of sea urchins, loss of predation can cause a trophic cascade that affects kelp forests and associated marine biodiversity229,230. Given the effects of ocean warming on pathogen impacts, temperature monitoring systems have been developed for a wide range of marine organisms, including corals, sponges, oysters, lobsters and other crustaceans, sea stars, fish and sea grasses231.

Forest die-off caused by drought and heat stress can be exacerbated by pathogens232. For crops, a variety of interacting factors are important when one is considering response to pathogens, including CO ₂ levels, climatic changes, plant health and species-specific plant-pathogen interactions233. A broad range of microorganisms cause plant diseases (fungi, bacteria, viruses, viroids and oomycetes) and can, therefore, affect crop production, cause famines (for example, the oomycete Phytophthora infestans caused the Irish potato famine) and threaten food security233. An assessment of more than 600 crop pests (nematodes and insects) and pathogens since 1960 found an expansion towards the poles that is attributable to climate change233. The spread of pathogens and the emergence of disease are facilitated by transport and introduction of species and are influenced by effects of weather on dispersal and environmental conditions for growth233.

Climate change can increase the disease risk by altering host and parasite acclimation234. For ectotherms (such as amphibians), temperature can increase susceptibility to infection, possibly through perturbation of immune responses234,235. Monthly and daily unpredictable environmental temperature fluctuations increase the susceptibility of the Cuban tree frog to the pathogenic chytrid fungus Batrachochytrium dendrobatidis. The effect of increasing temperature on infection contrasts with decreased growth capacity of the fungus in pure culture, illustrating the importance of assessing host-pathogen responses (rather than extrapolating from growth rate studies of isolated microorganisms) when evaluating the relevance of climate change234.

Climate change is predicted to increase the rate of antibiotic resistance of some human pathogens236. Data from 2013-2015 suggest that an increase of the daily minimum temperature by 10 °C (which is conceivable for some parts of the USA by the end of the century) will lead to an increase in antibiotic resistance rates of Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus by 2-4% (up to 10% for certain antibiotics)236. Potential underlying mechanisms include elevated temperatures facilitating horizontal gene transfer of mobile genetic elements of resistance, and increased pathogen growth rates promoting environmental persistence, carriage and transmission236. Population growth, which amplifies climate change, is also an important factor in contributing to the development of resistance236.

Vector-borne, foodborne, airborne, waterborne and other environmental pathogens may be particularly susceptible to the effects of climate change (Table 1). For vector-borne diseases, climate change will affect the distribution of vectors and hence the range over which diseases are transmitted, as well as the efficiency with which vectors transmit pathogens. Efficiency depends on the time between a vector feeding on an infected host and the vector becoming infectious itself. At warmer temperatures, this time can be reduced substantially, providing more opportunity for transmission within the vector's lifespan. Certain vector-borne diseases, such as bluetongue, an economically important viral disease of livestock, have already emerged in Europe in response to climate change, and larger, more frequent outbreaks are predicted to occur in the future241. For certain waterborne infections by pathogenic Vibrio spp., poleward spread correlates with increasing global temperature and lower salinity of aquatic environments in coastal regions (such as estuaries) caused by increased precipitation242. These changed conditions can promote the growth of Vibrio spp. in the environment242. Increasing sea surface temperatures also correlate with increases in Vibrio cholerae infections in Bangladesh243, infections with several human-pathogenic Vibrio spp. in the Baltic Sea region242 and the abundance of Vibrio spp. (including human pathogens) in the North Atlantic and North Sea244.

Malaria and dengue fever are two vector-borne diseases that are known to be highly sensitive to climate conditions, and thus their spatial distributions are expected to shift in response to climate change. Climate change can facilitate the spread of vector-borne pathogens by prolonging the transmission season, increasing the rate of replication of pathogens in the vector and increasing the number and geographic range of mosquitoes. This is especially the case for Aedes aegypti, the major vector of dengue, Zika, chikungunya and yellow fever viruses, which is currently limited to tropical and subtropical regions because it cannot survive cold winters. In combination with other mosquito-borne diseases (such as West Nile fever and Japanese encephalitis) and tick-borne diseases (such as Lyme disease), millions of people are predicted to be newly at risk under climate change.

Many infectious diseases, including several vector-borne and waterborne diseases, are strongly influenced by climate variability caused by large-scale climate phenomena such as the ENSO, which disrupts normal rainfall patterns and changes temperatures in about two thirds of the globe every few years. Associations with ENSO have been reported for malaria, dengue fever, Zika virus disease, cholera, plague, African horse sickness and many other important human and animal diseases.

Adaptation of species to their local environment has been studied less in microorganisms than in animals (including humans) and plants, although the mechanisms and consequences of adaptation have been studied in natural and experimental microbial populations255. Viral, bacterial and fungal pathogens of plants and animals (such as crops, humans and livestock) adapt to abiotic and biotic factors (such as temperature, pesticides, interactions between microorganisms and host resistance) in ways that affect ecosystem function, human health and food security255. The cyclic feedback between microbial response and human activity is well illustrated by the adaptation patterns of pathogenic agricultural fungi256. Because agricultural ecosystems have common global features (for example, irrigation, fertilizer use and plant cultivars) and human travel and transport of plant material readily disperse crop pathogens, 'agro-adapted' pathogens have a higher potential to cause epidemics and pose a greater threat to crop production than naturally occurring strains256. The ability of fungal pathogens to expand their range and invade new habitats by evolving to tolerate higher temperatures compounds the threat fungal pathogens pose to both natural and agricultural ecosystems257.

Microbial mitigation of climate change

An improved understanding of microbial interactions would help underpin the design of measures to mitigate and control climate change and its effects (see also ref.7). For example, understanding how mosquitoes respond to the bacterium Wolbachia (a common symbiont of arthropods) has resulted in a reduction of the transmission of Zika, dengue and chikungunya viruses through the introduction of Wolbachia into populations of A. aegypti mosquitoes and releasing them into the environment258. In agriculture, progress in understanding the ecophysiology of microorganisms that reduce N ₂O to harmless N ₂ provides options for mitigating emissions214,259. The use of bacterial strains with higher N ₂O reductase activity has lowered N ₂O emissions from soybean, and both natural and genetically modified strains with higher N ₂O reductase activity provide avenues for mitigating N ₂O emissions214. Manipulating the rumen microbiota260 and breeding programmes that target host genetic factors that change microbial community responses261 are possibilities for reducing methane emission from cattle. In this latter case, the aim would be to produce cattle lines that sustain microbial communities producing less methane without affecting the health and productivity of the animals261. Fungal proteins can replace meat, lowering dietary carbon footprints262.

Biochar is an example of an agricultural solution for broadly and indirectly mitigating microbial effects of climate change. Biochar is produced from thermochemical conversion of biomass under oxygen limitation and improves the stabilization and accumulation of organic matter in iron-rich soils263. Biochar improves organic matter retention by reducing microbial mineralization and reducing the effect of root exudates on releasing organic material from minerals, thereby promoting growth of grasses and reducing the release of carbon263.

A potentially large-scale approach to mitigation is the use of constructed wetlands to generate cellulosic biofuel using waste nitrogen from wastewater treatment; if all waste in China were used, it could supply the equivalent of 7% of China's gasoline consumption264. Such major developments of constructed wetlands would require the characterization and optimization of their core microbial consortia to manage their emissions of greenhouse gases and optimize environmental benefits265.

Microbial biotechnology can provide solutions for sustainable development266, including in the provision (for example, of food) and regulation (for example, of disease or of emissions and capture of greenhouse gases) of ecosystem services for humans, animals and plants. Microbial technologies provide practical solutions (chemicals, materials, energy and remediation) for achieving many of the 17 United Nations Sustainable Development Goals, addressing poverty, hunger, health, clean water, clean energy, economic growth, industry innovation, sustainable cities, responsible consumption, climate action, life below water, and life on land6 (Box 1). Galvanizing support for such actions will undoubtedly be facilitated by improving public understanding of the key roles of microorganisms in global warming, that is, through attainment of microbiology literacy in society7.

Conclusion

Microorganisms make a major contribution to carbon sequestration, particularly marine phytoplankton, which fix as much net CO ₂ as terrestrial plants. For this reason, environmental changes that affect marine microbial photosynthesis and subsequent storage of fixed carbon in deep waters are of major importance for the global carbon cycle. Microorganisms also contribute substantially to greenhouse gas emissions via heterotrophic respiration (CO ₂), methanogenesis (CH ₄) and denitrification (N ₂ O).

Many factors influence the balance of microbial greenhouse gas capture versus emission, including the biome, the local environment, food web interactions and responses, and particularly anthropogenic climate change and other human activities (Figs 1- 3).

Human activity that directly affects microorganisms includes greenhouse gas emissions (particularly CO ₂, CH ₄ and N ₂ O), pollution (particularly eutrophication), agriculture (particularly land usage) and population growth, which positively feeds back on climate change, pollution, agricultural practice and the spread of disease. Human activity that alters the ratio of carbon uptake relative to release will drive positive feedbacks and accelerate the rate of climate change. By contrast, microorganisms also offer important opportunities for remedying human-caused problems through improved agricultural outcomes, production of biofuels and remediation of pollution.

Addressing specific issues involving microorganisms will require targeted laboratory studies of model microorganisms (Box 2). Laboratory probing of microbial responses should assess environmentally relevant conditions, adopt a 'microbcentric' view of environmental stressors and be followed up by field tests. Mesocosm and in situ field experiments are particularly important for gaining insight into community-level responses to real environmental conditions. Effective experimental design requires informed decision-making, involving knowledge from multiple disciplines specific to marine (for example, physical oceanography) and terrestrial (for example, geochemistry) biomes.

To understand how microbial diversity and activity that govern small-scale interactions translate to large system fluxes, it will be important to scale findings from individuals to communities and to whole ecosystems. Earth system modellers need to include microbial contributions that account for physiological and adaptive (evolutionary) responses to biotic (including other microorganisms, plants and organic matter substrates) and abiotic (including mineral surfaces, ocean physics and chemistry) forcings.

We must improve our quantitative understanding of the global marine and soil microbiome. To understand biogeochemical cycling and climate change feedbacks at any location around the world, we need quantitative information about the organisms that drive elemental cycling (including humans, plants and microorganisms), and the environmental conditions (including climate, soil physiochemical characteristics, topography, ocean temperature, light and mixing) that regulate the activity of those organisms. The framework for quantitative models exists, but to a large extent these models lack mechanistic details of marine and terrestrial microorganisms. The reason for this omission has less to do with how to construct such a model mathematically but instead stems from the paucity of physiological and evolutionary data allowing robust predictions of microbial responses to environmental change. A focused investment into expanding this mechanistic knowledge represents a critical path towards generating the global models essential for benchmarking, scaling and parameterizing Earth system model predictions of current and future climate.

Extant life has evolved over billions of years to generate vast biodiversity, and microbial biodiversity is practically limitless compared with macroscopic life. Biodiversity of macroscopic organisms is rapidly declining because of human activity, suggesting that the biodiversity of host-specific microorganisms of animal and plant species will also decrease. However, compared with macroscopic organisms, we know far less about the connections between microorganisms and anthropogenic climate change. We can recognize the effects of microorganisms on climate change and climate change on microorganisms, but what we have learned is incomplete, complex and challenging to interpret. It is therefore not surprising that challenges exist for defining causes and effects of anthropogenic climate change on biological systems. Nevertheless, there is no doubt that human activity is causing climate change, and this is perturbing normal ecosystem function around the globe (Box 1). Across marine and terrestrial biomes, microbially driven greenhouse gas emissions are increasing and positively feeding back on climate change. Irrespective of the fine details, the microbial compass points to the need to act (Box 2). Ignorance of the role of, effects on and feedback response of microbial communities to climate change can lead to our own peril. An immediate, sustained and concerted effort is required to explicitly include microorganisms in research, technology development, and policy and management decisions. Microorganisms not only contribute to the rate of climate change but can also contribute immensely to its effective mitigation and our adaptation tools.

Box 2 A call to action

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Scientists' warning to humanity: microorganisms and climate change - Nature Reviews Microbiology

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The microbial majority with which we share Earth often goes unnoticed despite underlying major biogeochemical cycles and food webs, thereby taking a key role in climate change. This Consensus Statement highlights the importance of climate change microbiology and issues a call to action for all microbiologists.

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Bacteria have gotten a bad reputation, and for good reason. Bacteria are behind a number of serious diseases - including pneumonia ( Streptococcus pneumoniae), meningitis ( Haemophilus influenzae), strep throat ( Group A Streptococcus), food poisoning ( Escherichia coli and Salmonella),and a variety of other infections.

These "bad" bacteria are the reason why we diligently disinfect our hands and wipe down our kitchen and bathroom sinks, as well as any other places where germs tend to congregate. We also have developed a wide range of antibiotics, which are drugs designed to kill the bacteria that cause disease.

Yet, not all bacteria are bad guys. In fact, our bodies are home to an estimated 100 trillion "good" bacteria, many of which reside in our gut. Not only do we live in harmony with these beneficial bacteria, but they are actually essential to our survival.

Good bacteria help our bodies digest food and absorb nutrients, and they produce several vitamins in the intestinal tract - including folic acid, niacin, and vitamins B6 and B12. According to research published in the journal Best Practice & Research Clinical Gastroenterology, beneficial bacteria may also protect us against their dangerous relatives that cause disease by crowding them out in the gut, producing acids that inhibit their growth, and stimulating the immune system to fight them off.

When helpful bacteria multiply and thrive in our bodies, they act as our protectors. But sometimes, we put the population of beneficial bacteria at risk. When we take antibiotics to treat an infection of harmful bacteria, we also kill helpful bacteria. This can cause an imbalance of bacteria in the body that can lead to diarrhea and other gastrointestinal problems.

The idea that certain types of bacteria can improve our health has been around since the early 20 th century, when Nobel prize-winning Russian biologist Elie Metchnikoff first proposed that eating bacteria similar to those living in the body could have health benefits. More recently, companies started marketing products called probiotics (which means "for life") containing these bacteria.

Probiotics are available in many forms, including supplement pills, suppositories, and creams. Many foods contain friendly bacteria, such as:

yogurt

buttermilk

cheeses with live active cultures

Other foods that contain friendly bacteria include fermented foods such as:

Probiotics are proposed to prevent and treat a variety of health conditions, such as:

diarrhea (including diarrhea caused by
antibiotics)

irritable bowel syndrome

ulcerative colitis and Crohn's disease

tooth decay, gingivitis, and periodontitis

eczema

A few studies have hinted that probiotic pills might improve health, but many medical researchers such as those at the Cleveland Clinic report that there is not enough proof to say for sure.

Below are a few of the probiotics that are taken to treat or prevent disease, and how they're thought to work.

Lactobacillus

In the body, lactobacillus bacteria are normally found in the digestive, urinary, and genital systems. You can also find them in yogurt and dietary supplements, as well as in suppositories.

More than 50 different species of lactobacillus exist, including:

Lactobacillus acidophilus, one of the
most commonly used probiotics. It's found in yogurt and fermented soy products
such as miso and tempeh. Lactobacillus acidophilus has been
used (in suppository form) to treat bacterial infections of the vagina. In pill
form, it can be taken to prevent and treat diarrhea, including traveler's
diarrhea in adults and diarrhea caused by rotavirus in children.

Lactobacillus rhamnosus GG may help treat
traveler's diarrhea, or diarrhea that's caused by Clostridium difficile
(C. difficile) bacteria or by antibiotics in children. It's also
been found to help prevent eczema in infants.

Lactobacillus salivarius may help
block the growth of Helicobacter pylori (H. pylori),
the bacteria that cause peptic ulcers.

Lactobacillus plantarum can improve
the immune system barrier against invading disease-causing bacteria.

Other uses for lactobacillus include:

preventing diarrhea caused by antibiotics and
infection

preventing colic (inconsolable crying) in babies

preventing lung infections in young children

preventing diarrhea in adults who are in the
hospital or receiving chemotherapy treatment for cancer

treating bowel conditions such as irritable
bowel syndrome (IBS) and ulcerative colitis

Bifidobacteria

Bifidobacteria make up most of the "good" bacteria living in the gut. These bacteria begin colonizing the gastrointestinal system almost immediately after we're born.

Bifidobacteria come in about 30 different strains, including:

Bifidobacteria bifidum may help
protect against unhealthy bacteria. suggests they
also can relieve IBS symptoms. When combined with Lactobacillus
acidophilus, Bifidobacteria bifidum might help prevent eczema in
newborns.

Bifidobacteria infantis are thought
to help relieve the symptoms of IBS, such as abdominal pain, gas, and bloating

Bifidobacteria lactis has been
reported to improve cholesterol levels in women and in people with type 2
diabetes.

Streptococcus thermophilus

These bacteria produce the enzyme lactase, which the body needs to digest the sugar in milk and other dairy products. Some studies suggest Streptococcus thermophilus can help prevent lactose intolerance.

Saccharomyces boulardii

Saccharomyces boulardii is actually a type of yeast, but it acts as a probiotic. Some studies have found it helpful for preventing and treating traveler's diarrhea, as well as diarrhea caused by antibiotics. It may also be useful for treating acne, and reducing the side effects of antibiotic treatment for H. pylori bacteria.

Before you take any probiotic supplement, remember that the U.S. Food and Drug Administration (FDA) has not approved these products. That means you can't be sure when you buy a product whether it's safe and effective. There have been cases reported of people developing bacteria (bacteremia) or fungi (fungemia) in the blood after taking probiotics. More clinical studies are needed to confirm the benefits of probiotics, as well as the possible risks.

Let your doctor and pharmacist know before you take any probiotic supplement. Ask whether it's safe for people with your health conditions, and if it will interact with other medications you are already taking. It's especially important to tell your doctor before using these supplements if you are pregnant or nursing, have a weakened immune system from a condition such as HIV/AIDS, or are taking drugs that suppress your immune system.

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Good vs. Bad Germs: Here's What You Should Know

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Bacteria have gotten a bad reputation, and for good reason. Bacteria are behind a number of serious diseases - including pneumonia ( Streptococcus pneumoniae), meningitis ( Haemophilus influenzae), strep throat ( Group A Streptococcus), food poisoning ( Escherichia coli and Salmonella),and a variety of other infections.

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However, each probiotic can have different effects on your body. We read the names of bacteria with different foreign titles on the packaging, which often tells us nothing.

There is extremely little information about the different species (also called types and strains) of good bacteria, and because you should not grope in the dark, we bring you the results of research on the effects of the most studied and well-known bacterial species of good bacteria and their effects on the human body.

So, what are the species and benefits of these good bacteria and how do probiotics differ?

Strains of lactic acid bacteria are the most common microbes engaged as probiotics, especially Lactobacillus and Bifidobacterium species, but lactococci, some enterococci and some streptococci are also included as probiotics.

Bifidobacterium isn't included within the common Lactic Acid Bacteria thanks to its genetic insignificance , but the bacterium features a habitat that overlays with LAB (lactic acid bacteria), and it has a metabolism that makes lactic acid.

These two types of good bacteria Lactobacillus and Bifidobacterium in turn divide into different species:

Lactobacillus species - Of the more than 100 Lactobacillus species, the following are commonly used probiotics: Lactobacillus acidophilus, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus paracasei, Lactobacillus gasseri, Lactobacillus reuteri, Lactobacillus salivarius, Lactobacillus helveticus

Bifidobacterial species - Among 30 species, those recognized as probiotics include: Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium infantis, Bifidobacterium lactis, Bifidobacterium breve, Bifidobacterium adolescentis.

Streptococcus thermophilus

Types of Good Bacteria (Probiotics) - Lactobacillus (Lactic Acid bacteria) Species

The most important and predominant good bacteria that live mainly in the human small intestine are lactic bacteria (Lactobacillus). Lactobacillus is a family of Gram-positive, facultative anaerobic, rod-shaped bacteria. This group of lactic acid bacteria is responsible for the production of lactase.

Lactase is an enzyme that breaks down carbohydrates such as lactose (milk sugar) and other sugars into lactic acid. Similarly, l actic acid helps to create an acidic environment in the gastrointestinal tract, which inhibits the development of many unwanted microorganisms.

These good bacteria protect the body from allergic reactions, ensure timely bowel movements, prevent dysbiosis, relieve constipation, treat diarrhea, help the body develop elements of the immune system and play an important role in creating a favorable environment for bifidobacteria to multiply.

Even more, lactic bacteria (Lactobacillus) can inhibit the growth of cancer cells in the colon and mammary glands by preventing the body from being contaminated with pathogenic flora.

What does Gram-Positive Mean? Gram-positive bacteria, unlike Gram-negative bacteria retain the color of the crystal violet stain in the Gram stain.

10 Lactobacillus Species

1. Lactobacillus acidophilus

Lactobacillus acidophilus is one of the most important strains of Lactobacillus in the group of lactic acid bacteria. This bacterium lives most often in the small intestine, where it helps maintain a healthy intestinal wall to ensure the necessary absorption of nutrients and function of the overall digestive system.

Acidophilus strain helps relieve indigestion. A controlled double-blind placebo trial showed that those patients who used the probiotic strain of acidophilus experienced significantly fewer symptoms of indigestion than those who received placebo.

One separate meta-analysis found, that probiotic food supplements containing an acidophilus strain help relieve Research also shows that acidophilus helps to improve the activity of the diarrhea. The third study also found that food supplements containing both L. acidophilus and B. bifidum helped to reduce the harmful effects of antibiotics on the intestinal microflora. immune system and support the health of women's vaginal microflora.

Lactobacillus acidophilus benefits:

Supports all digestive function

Enhances absorption of nutrients

Relieves abdominal cramps, gases and diarrhea

Supports the health of the immune system and urinary tract

Improves vaginal microflora in women

2. Lactobacillus fermentum

Lactobacillus fermentum benefits:

3. Lactobacillus plantarum

L. plantarum is known for its ability to produce hydrogen peroxide. The body uses hydrogen peroxide as a line of defense against bacteria in food, as well as other microorganisms. Studies have also found that this strain helps effectively support immune function in healthy adults.

Lactobacillus plantarum benefits:

4. Lactobacillus rhamnosus

L. rhamnosus is one of the most studied strains of lactic bacteria in the world, and to date its beneficial properties have been proven in more than 260 clinical trials. The most important feature of this strain is the strengthening of the human immune system, which helps to prevent respiratory diseases (cough, runny nose, asthma, etc.), the risk of dental caries, prevent gastrointestinal infections and promote faster recovery from gastrointestinal infections.

Likewise, L. rhamnosus reduces the risk of developing allergic diseases and promotes faster relief of already severe atopic dermatitis. Above all, this probiotic strain is known for its great ability to survive through the gastrointestinal tract and is considered the best aid in supporting women's vaginal health among lactobacilli.

Even more, the study concluded that L. rhamnosus also helps to improve vaginal and urinary tract health and reduce vaginal irritability. Rhamnosus is also one of the best bacterial strains to take with you on a vacation. U.S. studies showed that those living in New York who consumed the L. rhamnosus strain when traveling to developing countries had a diarrhea incidence rate of 3.9%, compared with those who did not, and who had a rate of 7.4%.

Lactobacillus rhamnosus benefits:

Affects the human ability to protect against diseases and strengthens the immune system

Prevents respiratory diseases (cough, runny nose, asthma, etc.) and the risk of dental caries

Reduces the risk of allergic diseases

Helps prevent gastrointestinal infections (eg diarrhea when traveling to developing countries)

Reduces the side effects of antibiotic and chemotherapy treatment, and helps with IBS (irritable bowel syndrome)

Improves women's vaginal health

5. Lactobacillus paracasei

Lactobacillus paracasei is a strong strain living mainly in the small intestine. This probiotic strain of paracasei has a unique ability to support liver function and lower urine pH.

Lactobacillus paracasei benefits:

6. Lactobacillus gasseri

L gasseri is a relatively new bacterium among probiotic strain species. This lactic acid bacteria is predominantly associated with the vaginal microflora.

Lactobacillus gasseri benefits:

7. Lactobacillus reuteri

L. reuteri bacteria are located in both, in the intestines and the oral cavity. Studies in humans have shown that the bacterium L. reuteri supports the health of the gastrointestinal tract, oral microflora and immune system.

Lactobacillus reuteri benefits:

Supports the health of the gastrointestinal tract

Improves oral microflora

Strengthens immune system

8. Lactobacillus salivarius

L. salivarius is a somewhat unique bacteria because it is able to grow in poorer conditions than other lactic acid bacteria, including high-salt environments, and with or without oxygen.

Even more, to keep the human body healthy and functional, L. salivarius itself produces the necessary antibiotics. These antibiotics are specifically directed against the invasion of pathogenic bacteria that can cause dysbiosis and other health conditions.

L. salivarius also produces lactic acid, which creates an environment unsuitable for bad bacteria and an ideal environment for the necessary lactic acid bacteria.

Compared to other strains of probiotics, L. salivarius grows very rapidly. As a result, it quickly displaces bad bacteria. Salivarius has been found to be an excellent aid in protein digestion. It is a very resistant bacteria that is important for the health of all of us.

Lactobacillus salivarius benefits:

Helps to inhibit yeast infections, for example candida

Reduces gingivitis

Prevents strep throat (caused by S. Pyogenes)

Helps to reduce mastitis (inflammation of the breast), ulcerative colitis and irritable bowel syndrome (IBS)

Inhibits pathogenic bacteria such as E. coli and Salmonella spp.

Side effects of Lactobacillus salivarius are usually mild, such as a mild rash or temporary indigestion.

9. Lactobacillus helveticus

In the case of the Lactobacillus helveticus strain, it is a very interesting fact that it can lower blood pressure. This strain is widely used in cheese production in Switzerland.

Lactobacillus helveticus benefits:

10. Lactobacillus bulgaricus

The bacteria L. Bulgaricus was one of the first probiotic strains in history that was studied. Ilya Mechnikov, a Russian Nobel laureate, first isolated the Lactobacillus bulgaricus strain from fermented sour milk in 1882 when he discovered that the longevity of the Balkan people was due to eating fermented foods (fermented sour milk, kefir, sauerkraut, etc.).

L. Bulgaricus is a great help for those who are lactose intolerant and do not have an enzyme in the digestive system that helps break down lactose into easier sugar.

One random double-blind, placebo-controlled trial showed that consumption of beverages containing a probiotic complex such as L. casei, L. bulgaricus, and S. thermophilus reduced the incidence of Clostridium difficile, which is a diarrhea associated with side effects in antibiotic treatment.

It has been found that using such a combination of probiotics over the age of 50 would help reduce mortality and save on health care costs.

In addition, in the 1960s and 1970s, Russian scientists with Dr. Ivan Bogdanov conducted extensive research in the field of L. bulgaricus. They published a complete list of the benefits of the probiotic strains of L. bulgaricus, which are listed below.

Lactobacillus bulgaricus benefits:

Lowers blood levels of triglycerides and total cholesterol

Boosts immune system and fights viruses

Reduces leaking bowel symptoms, diarrhea and nausea

Improves the digestion of dairy products (lactose)

Reduces inflammation

Improves the symptoms of IBS (irritable bowel syndrome)

Reduces tooth decay

Manages HIV symptoms

Fights dyspepsia. Functional dyspepsia is a persistent or episodic indigestion that originates in the upper gastrointestinal tract and shows no signs of an organic disease (eg, ulcer, tumor).

Types of Good Bacteria (Probiotics) - Bifidobacteria (Bifidobacterium) Species

Bifidobacteria are a family of Gram-positive, anaerobic branched rod-shaped bacteria. Billions of bifidobacteria, located mainly in the walls of the colon help prevent the spread of harmful bacteria and other pathogenic microorganisms, including yeast, and their occupation in the intestinal wall.

Bifidobacteria is the largest group of bacteria in the intestines of infants, in adults bifidobacteria are in the 3 or 4 place, and their proportion decreases further with age.

Like lactic bacteria, bifidobacteria also produce lactic acid and acetic acid, which provide up to 70 percent of the energy needed for intestinal wall cells to increase the natural protective barrier in the gut.

Even more, Bifidobacteria break down lactose, synthesize amino acids and proteins, lower cholesterol, produce K and B complex vitamins, and help prevent food poisoning.

However, studies have shown that with age, stress and malnutrition, the number of bifidobacteria in the body begins to decrease. The most important strains of bifidobacteria are B. lactis, B. bifidum, B. longum, B. infantis, B. breve.

6. Bifidobacteria Species

1. Bifidobacterium bifidum

This probiotic strain is among the first to occupy the intestinal walls of infants and continues to do so throughout life as one of the major groups of bacteria in the entire colon microflora and in the small intestine.

By creating a balanced intestinal microflora, B. bifidum also helps to prevent the growth of unwanted bacteria, fungi and yeast by attaching to the intestinal mucosa better than strains of pathogenic bacteria. The role of the B. bifidum strain is also to help break down digestible carbohydrates, fats and proteins.

Bifidobacterium bifidum benefits:

Supports whole digestive function

Helps to absorb nutrients

Helps in case of random diarrhea, for example travel diarrhea.

2. Bifidobacterium longum

The B. longum strain is one of the most common bifidobacteria found in the gastrointestinal tract. Its effect on digestion is the ability to break down carbohydrates and neutralize toxins in the gut.

Preliminary studies have shown that the B. longum strain has antioxidant properties. For example, this bacteria can remove metallic minerals such as copper and corrosive free radicals from the body.

Even more, the studies showed that, after 20 weeks of taking the B. longum, there was an increase in immune parameters in the elderly. Therefore, it also has a supportive effect on the immune system.

Bifidobacterium longum benefits:

3. Bifidobacterium infantis

Among other beneficial bacteria, this probiotic strain has the highest colony especially in babies. The amount of B. infantis decreases with age, but still it remains an important bacteria in our microflora. A dietary supplement with a strain of B. infantis has been shown to reduce bloating, constipation and bowel movement difficulties.

Bifidobacterium infantis benefits:

4. Bifidobacterium lactis also called Bifidobacterium animalis

B. lactis live in large numbers in the intestine and colon. In general, the function of B. lactis is to break down body residues and help the body absorb various vitamins and minerals. Bifidobacterium lactis is also widely used in the production of cheese, curd and butter.

Bifidobacterium lactis benefits:

5. Bifidobacterium breve

Bifidobacterium breve benefits:

Reduces chronic periodontitis, a microbial inflammation of the supporting tissues of the teeth

Treats oral ulcers

Reduces urinary oxalate levels (oxalate forms water-insoluble crystals that can form kidney stones, for example from excessive consumption of ascorbic acid)

Decreases helicobacter pylori colonization

6. Bifidobacterium adolescentis

Bifidobacterium adolescentis is a natural component of the gut of every healthy person and occupies the gut immediately after birth. Their population remains relatively stable until late adulthood.

Since then, the presence of lactic acid bacteria in the gut has been associated with a healthy microflora.

Bifidobacterium adolescentis benefits:

Streptococcus thermophilus

Streptococcus thermophilus is a very powerful strain of lactic acid bacteria that has also been extensively studied. This probiotic strain is located mainly in the colon and has a strong effect on the gastrointestinal tract, immune system and many other health-improving factors.

S. thermophilus is used in the production of cheese and yoghurt and it also produces lactase, which helps break down milk sugar (lactose). Streptococcus thermophilus also produces body-specific antibiotic chemicals that help prevent intestinal ulcers, pneumonia and antibiotic-induced C. Difficile.

Streptococcus thermophilus benefits:

Probiotics Side Effects and Avoiding Dysbiosis (Microbial Imbalance)

The side effects of probiotics mean that good bacteria have started to work! However, the most common side effects that can sometimes occur can be

Assuming that the side effects of probiotics are relatively small and the symptoms do not last more than 14 days, there is reason to be joyful because of these side effects!

It's because temporary reactions such as mild bloating, diarrhea or constipation indicate that harmful bacteria that can cause dysbiosis are being replaced by beneficial ones, waste products are excreted from the gut, and the intestinal environment is improved and healed.

It should also be remembered that although these side effects are unpleasant, they are much milder compared to many drug-related side effects.

Here are 3 ways to reduce the side effects of probiotics

Dose reduction

One way to reduce the side effects is to reduce the dose. Take one capsule instead of two until your body gets used to the new good bacteria. Once the body is used to it, you can increase the dose again. The overdose of probiotics can cause too rapid CFU in the gut, which means the number of viable bacteria or fungal cells in the sample.

Water consumption

Give your body time to adjust

Taking probiotics can kill a large number of bad bacteria by replacing them with useful ones. However, this can be quite a shock to the body. Therefore, just allow your body to get used to it for at least two weeks until the side effects go away. If the side effects do not go away, see a doctor.

Probiotics, which ones to consume?

The intestinal microflora varies according to age and the health condition, so the need for probiotics may therefore differ. Hence, you should always read the labels of the product.

Maria-Helena Loik

Sources: Fda.gov/BiologicsBloodVaccines, Ncbi.nlm.nih.gov, Textbookofbacteriology.net, Gutmicrobiotaforhealth.com, Probiotics101.probacto.com, Probiotics.org, Globalhealingcenter.com, Drdavidwilliams.com, Microbewiki.kenyon.edu, Sumobrain.com, Bmccancer.biomedcentral.com, Probioticsdb.com

Pictures: Pixabay.com, Pexels.com, Shutterstock.com

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17 TYPES OF GOOD BACTERIA - The List of Most Beneficial Species of Probiotics Lactobacillus and Bifidobacteria - Ecosh Life

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However, each probiotic can have different effects on your body. We read the names of bacteria with different foreign titles on the packaging, which often tells us nothing.

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Révéler ce qui est invisible à l’oeil nu

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critique sur la grande quantité d'images de violence diffusées et disponibles à tous

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La collection «THIS IS THE END OF YOU» propose une réflexion sociétale sur la violence qui nous est présentée quotidiennement. Par l’intérim de 32 images tirées de scènes de films ou de séries télévisées mettant de l’avant un personnage pointant son arme aux spectateurs (à la caméra), l’oeuvre a comme objectif de créer un inconfort pour l’observateur, lui imposant une forme de violence directe qui est pourtant omniprésente de nos jours. Il ne s’agit pas d’une critique, mais plutôt d’une ouverture pour une discussion quant aux impacts des images violentes que nous présentons autant dans les médias que dans l’industrie cinématographique.

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répertoire de 52 «screenshots» ou images tirés de films ou de séries télévisées. à gauche (fusil pointé vers droite caméra), centre (fusil centré), à droite (fusil pointé vers la gauche caméra), bas de la page (images rejetées)

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https://sammlung.staedelmuseum.de/en

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About the
Städel Museum

Established as a civic foundation in 1815 by the banker and businessman Johann Friedrich Städel, the Städel Museum ranks as Germany's oldest museum foundation. Under a single roof, its collection offers a virtually complete survey of seven hundred years of European art from the early fourteenth century to the present, with focuses on the Renaissance, the Baroque, early Modern art and much more.

Visit the Städel Museum

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Established as a civic foundation in 1815 by the banker and businessman Johann Friedrich Städel, the Städel Museum ranks as Germany's oldest museum foundation. Under a single roof, its collection offers a virtually complete survey of seven hundred years of European art from the early fourteenth century to the present, with focuses on the Renaissance, the Baroque, early Modern art and much more.

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https://fraenkelgallery.com/artists/christian-marclay

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Christian Marclay is a London and New York based visual artist and composer whose innovative work explores the juxtaposition between sound recording, photography, video and film. Marlcay was born in California in 1955 and raised in Geneva, Switzerland. His mother was American so he held a double nat…

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Christian Marclay

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définition:
La dysmorphophobie est caractérisée par une préoccupation concernant ≥ 1 défaut perçu de l'apparence physique qui ne sont pas apparents ou apparaissent léger à d'autres personnes. La préoccupation concernant l'apparence doit provoquer des souffrances ou des perturbations importantes de la vie sociale, professionnelle, scolaire ou dans d'autres domaines de fonctionnement. Et à un certain moment au cours de l'évolution de la maladie, les patients doivent de manière répétitive et excessive effectuer ≥ 1 comportements répétitifs (p. ex., vérification devant le miroir, en comparant leur apparence avec celle d'autres sujets) en réponse à des préoccupations d'apparence. Le diagnostic repose sur l'anamnèse. Le traitement repose sur des médicaments (en particulier les inhibiteurs sélectifs de la recapture de la sérotonine ou la clomipramine) et/ou la psychothérapie (en particulier la thérapie cognitivo-comportementale).