Evidence for a signaling system in Helicobacter pylori: detection of a luxS-Encoded autoinducer

Helicobacter pylori possesses a homolog of the luxS gene, initially identif ied by its role in autoinducer production for the quorum-sensing system 2 i n Vibrio harveyi. The genomes of several other species of bacteria, notably Escherichia coil, Salmonella enterica serovar Typhimurium, and Vibrio chol erae, also include luxS homologs. All of these bacteria have been shown to produce active autoinducers capable of stimulating the expression of the lu ciferase operon in V. harveyi. In this report, we demonstrate that H. pylor i also synthesizes a functional autoinducer (AI-2) that can specifically ac tivate signaling system 2 in V. harveyi. Maximal activity is produced durin g early log phase, and the activity is diminished when cells enter stationa ry phase. We show that AI-2 is not involved in modulating any of the known or putative virulence factors in H. pylori and that a luxS null mutant has a two dimensional protein profile identical to that of its isogenic parent strain. We discuss the implications of having an AI-2-like quorum-sensing s ystem in H. pylori and suggest possible roles that it may play in H. pylori infection.