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Cells grow and divide

Bacteria keep us alive

Able to distinguish between being alone and being in a community by making and secreting small molecules similar to hormones

Bacterium have signal producing hormone and signal receptor protein which triggers the group behaviour

This is called Bacterial Quorum Sensing

This is the mechanism for bacterial infection - once the bacteria invades the host it multiplies until there is a sufficient number of cells, which can be identified by the release the molecule and carry out a pathogenic attack

This is a mode of intraspecies communication

Each bacteria also has a second enzyme which makes a second signal and has its own receptor and this is the mode of interspecies communication - every bacterium has this enzyme which produces the same molecule (small 5 carbon molecule)

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Bacteria communicate both intra-species and inter-species

"Quorum sensing is a mechanism of microbial communication wherein microorganisms synchronize their behavior depending on the population density (Miller & Bassler, 2001)".

It allows bacterial cell-to-cell signalling that controls the factors in many pathological bacteria.

The three main targets of quorum sensing proposed are;

1. The signal generator

2. The Quorum-sensing molecule

3. The signal receptor

By disrupting one of these targets, it can reduce the ability for cell-to-cell communication and prevent the release of virulent in a host.

The development of antimicrobial pharmaceuticals has allowed us to effectively treat various infectious diseases since the discovery of penicillin in 1928. Meaning traditional methods is to kill the bacterium and allowing the growth of resistant bacterium, where Quorum Sensing will be to prevent their communication, to prevent the production of bio-films and virulence in a host as an example.

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Way more bacteria in humans than human cells

Quorum sensing is a chemical form of communication and occurs in both a form of intraspecies and interspecies communication

Quorum Sensing is integral in regulating pathogenicity

Squid are the stealth bombers of the sea

This principle can be inhibited in order to prevent bateria from undergoing pathogensis

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- Bacteria has a very significant role in bodily functions and keeps us alive
- Bacteria talk to each other by secreting signal molecules (often called auto-inducers - like hormones)
- Regulation of gene expression - coordinate the expression of certain genes
- Detect and respond to cell population density
- discovered through the study of bioluminescence in Vibrio fischeri

- Intraspecies communication:

chemical secretion and detection is specific to the species of bacteria
- Interspecies communication: bacteria can take census and communicate with all other types of bacteria. They have a generic enzyme which makes a second signal used by all bacteria.
- Information from both intraspecies and interspecies communication allows bacteria to make decisions on behaviour

Practical Application
- Bacteria initiate pathogenicity by producing virulence factors
- Bacteria are becoming multi-drug resistant
- Target intraspecies communication which lock into the receptors
- Specific anti-quorum sensing molecules
- Broad spectrum antibiotics

- On the other side we can enhance bacteria which are beneficial

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Overview Bacteria

Consume nutrients then grow and divide

10 x more bacterial cells than normal cells

100 x more bacterial genes

keep out environmental factors, digest food etc

Vibrio Fischeri

In dilute concentrations made no light

produce light when together  in higher concentrations through quorum sensing

secretes molecules that increase in proportion to cell number

Quorum specific receptors sense either a species specific quorum or a universal quorum for all bacteria

Potential

Potential for new type of antibiotic (Quorum sensing inhibitors) to inhibit pathogenicity of bacteria

Can inhibit intra-species communication (specific)

Can inhibit universal bacterial communication (general)

Can also be used to promote bacterial activity in GIT t