Question

If a vibrio strain lacking LuxN and CqsS is co-cultured with another strain lacking only LuxS, both at high density, will bioluminescence be produced?

A) No

B) Yes

Answer 1

No

In bacterial quorum sensing, signal molecules termed autoinducers are used for bacterial communication. For eg., in the marine bacterium, Vibrio harveyi two parallel quorum-sensing systems have been identified. System 1 comprises of the LuxM-dependent autoinducer HAI-1 and the HAI-1 sensor, LuxN. System 2 consists of the LuxS-dependent autoinducer AI-2 and the AI-2 detector, LuxPQ. The related one, Vibrio cholerae, a human pathogenic Vibrio strain, contains System 2 (LuxS, AI-2, and LuxPQ) but does not possess obvious homologs of V. harveyi System 1. Instead, System 1 of V. cholerae is made up of the CAI-1(CqsA-dependent autoinducer) and a sensor called CqsS. Using a V. cholerae CAI-1 reporter strain, some Vibrio strains including V. harveyi, produce CAI-1 activity. Genetic analysis of V. harveyi shows cqsA and cqsS, and phenotypic analysis of V. harveyi cqsA and cqsS mutants shows that these functions possess a third V. harveyi quorum-sensing system that acts in parallel to Systems 1 and 2. Together these communication systems act as a 3-way coincidence detector in the regulation of a variety of genes, including those responsible for bioluminescence.