Question

Microbiology question:
Why would quorum sensing be associated with bioluminescence?

microbiology

Answer 1

Quorum sensing(Autoinduction) is the regulation of gene expression in response to fluctuations in population density and Bioluminescence is the production and emission of light by a living organism.

Quorum sensing should be associated with bioluminescence, because it is a way to communicate for bacteria and to determine where to nest. Quorum sensing is a diffusible pheromone produced by bioluminescent bacteria and serves as an extracellular signalling molecule and  it induces the expression of luciferase and other enzymes involved in bioluminescence.

Bacteria are able to estimate their population density in the surrounding environment by sensing the level of quorum sensor around it which thereby regulate their bioluminescence. The bioluminescence produced will be visible in the environment only at sufficiently high cell population.

For example, quorum sensing is that which occurs between Aliivibrio fischeri and its host. The genes LuxI and LuxR, are regulate this process and encoded by luxI and luxR respectively. LuxI is autoinducer synthase that produces autoinducer (AI) while LuxR functions as both a receptor and transcription factor for the lux operon. When LuxR binds AI, LuxR-AI complex activates transcription of the lux operon and induces the expression of luciferase. Using this system, A. fischeri has shown that bioluminescence is expressed only when the bacteria are host-associated and have reached sufficient cell densities.