Question

Diagram (draw and describe) the regulation of the lux operon in Vibrio fishcerii. Why is quorum sensing important for these bioluminescent, mutualistic bacteria? What is the benefit to the Hawaiian Bobtail Squid?

LUX OPERON

Answer 1

Operon cell extenor cell interior I Luxd -Steuer un | CDARBO Luxl synthesizes autoinducea All-3- Onohen anoyl-4-homoserine lactone), 8t binds to Lux R which es an transcriptional activator of luminescente genes lux CDABE

• Quorum sensing (QS) is the communication between bacterial cells to alter its group behaviour according the population density. This depends on the signalling molecules such as autoinducers present in the environment.
• In Vibrio fischeri, QS is important to form a mutualistic symbiosis with Hawaiian bobtail squid.
• This Vibrio fischeri consists of two quorum-sensing systems namely ain and lux. Here acyl homoserine lactones acts as signaling molecules.
• ain system activates the expression of luminescence gene at low cell densities when compared to lux system actication and both are important for continuous colonization of squid host.
• ain in inactive condition and lux activated, delays symbiotic relationship initiation.

• Benefit: Both Vibrio fischeri and Hawaiian bobtail squid benefits from the symbiotic relationship.
• The bacteria has home and food which doesnot affect the Hawaiian bobtail squid (animal). The animal benefit from the bacteria, where the animal fools its predator with the help of lumiescence producing bacteria that mimics the moonlight.