• Survival strategies that bacteria use and include bioluminescence virulence factor production, sporulation, biofilm formation and motility

--> cannot bind to Lux R = inactive = cannot bind to lux promoter = lux operon is not switch on

--> no gene expression of lux operon = behaviors like bioluminescence do not happen

• bacteria like Vibrio fischeri remain “dark”

• Save energy and ensure bioluminescence is not wasted

  
  

• At low bacterial density, the bacteria inside the squid don’t glow, keeping the squid safe from predators. As the bacteria grow, they start to glow, helping the squid blend in and hide

Quorum sensing is one of the processes used by bacteria to coordinate their behavior based on the population density.

Some functions regulated by quorum sensing include:

1) Biofilm formation

• Quorum sensing helps bacteria to form biofilms, which are protective layers that help them survive in harsh conditions.

2) Virulence factor production

• Some pathogenic bacteria use quorum sensing to regulate the production of toxins and other factors that enhance their ability to cause disease.

3) Sporulation

• In some bacterial species, quorum sensing controls the formation of endospores, which are high resistant forms of bacteria.

4) Antibiotic resistance

• Bacteria can use quorum sensing to develop and share resistance to antibiotics, making infections more difficult to treat.

5) Bioluminescence

• Certain marine bacteria use quorum sensing to produce light, which can be used for attracting prey for symbiotic relationships with marine organisms.

6) Conjugation

• The process of genetic exchange between bacteria. Quorum sensing can regulate the expression of genes involved in conjugation, allowing bacteria to share genetic material such as plasmids.

7) Motility

• Quorum sensing can control the movement of bacteria, enabling them to move collectively towards a favorable environment or away from harmful conditions.

• Bacteria first attach themselves to a surface using their appendages like pili or fimbriae.

2) Irreversible attachment to the surface due to EPS production.

• Once a critical number of bacteria have attached, they start producing extracellular polymeric substances (EPS), a sticky substance that firmly anchors them to the surface and to each other.

3) Microcolony formation and multi-layer of cells adhering to one another.

• The bacteria continue to multiply and produce more EPS, forming structured communities. During this stage, the cells communicate through quorum sensing by releasing signaling molecules called autoinducers. When the concentration of these molecules reaches a certain threshold, it triggers the expression of specific genes involved in biofilm formation.

4) Mature biofilm with characteristic ‘mushroom’ architecture supported by EPS.

• The biofilm develops a complex, three-dimensional structure with water channels that allow nutrients and waste to be transported. The bacteria within the biofilm can differentiate into distinct subpopulations, each with specialized functions.

5) Detachment and reversal to planktonic growth.

• Eventually, some bacteria within the biofilm will receive signals (often through quorum sensing) to become motile again and disperse from the biofilm. This allows them to colonize new surfaces and form new biofilms.

2) Close proximity of bacteria in the biofilm allows efficient synergistic microbial growth

For example, different species may cooperate to break down a common substrate into usable nutrients Also. different species may exchange metabolites and catalyze them further in another pathway. Thus, giving biofilm systems higher metabolic efficiency by maximally utilizing. waste products and makes nutrient sources available for the microorganisms to support their growths.

3) Close proximity of bacteria in the biofilm allows efficient intra- and interspecies cell-cell communication. For example, Al-2 may trigger the production of bacterial surface adhesins and induces coaggregation. between different bacterial species. Also, quorum sensing may increase EPS production in the attached cells. Thus, enhancing biofilm formation.

4) Close proximity of bacteria in the biofilm also creates a favorable condition for genetic material exchange that may enhance survivability by producing populations with antibiotic resistance or higher pathogenicity- (that is ability to cause disease).