Intercellular signalling in <i>Vibrio harveyi</i>: sequence and function of genes regulating expression of luminescence

TLDR

Density‑dependent luminescence in *Vibrio harveyi* is controlled by extracellular autoinducer concentration, with LuxL and LuxM proteins unique to this system and LuxN resembling a two‑component signal‑transduction kinase. Sequence analysis identified three open reading frames—luxL and luxM required for autoinducer synthesis and luxN required for signal response. A recombinant clone that restored luminescence in dim mutants encoded these functions, and mutant phenotypes for luxL, luxM, and luxN suggest an additional, yet unidentified, signal‑response system.

Abstract

Summary Density‐dependent expression of luminescence in Vibrio harveyi is regulated by the concentration of an extracellular signal molecule (autoinducer) in the culture medium. A recombinant clone that restored function to one class of spontaneous dim mutants was found to encode functions necessary for the synthesis of, and response to, a signal molecule. Sequence analysis of the region encoding these functions revealed three open reading frames, two ( luxL and luxM ) that are required for production of an autoinducer substance and a third ( luxN ) that is required for response to this signal substance. The LuxL and LuxM proteins are not similar in amino acid sequence to other proteins in the database, but the LuxN protein contains regions of sequence resembling both the histidine protein kinase and the response regulator domains of the family of two–component, signal transduction proteins. The phenotypes of mutants with luxL, luxM and luxN defects indicated that an additional signal–response system controlling density‐dependent expression of luminescence remains to be identified.