title: The LuxS-dependent autoinducer AI-2 controls the expression of an ABC transporter that functions in AI-2 uptake in Salmonella typhimurium.
abstract: In a process called quorum sensing, bacteria communicate with one another using secreted chemical signalling molecules termed autoinducers. A novel autoinducer called AI-2, originally discovered in the quorum-sensing bacterium Vibrio harveyi, is made by many species of Gram-negative and Gram-positive bacteria. In every case, production of AI-2 is dependent on the LuxS autoinducer synthase. The genes regulated by AI-2 in most of these luxS-containing species of bacteria are not known. Here, we describe the identification and characterization of AI-2-regulated genes in Salmonella typhimurium. We find that LuxS and AI-2 regulate the expression of a previously unidentified operon encoding an ATP binding cassette (ABC)-type transporter. We have named this operon the lsr (luxS regulated) operon. The Lsr transporter has homology to the ribose transporter of Escherichia coli and S. typhimurium. A gene encoding a DNA-binding protein that is located adjacent to the Lsr transporter structural operon is required to link AI-2 detection to operon expression. This gene, which we have named lsrR, encodes a protein that represses lsr operon expression in the absence of AI-2. Mutations in the lsr operon render S. typhimurium unable to eliminate AI-2 from the extracellular environment, suggesting that the role of the Lsr apparatus is to transport AI-2 into the cells. It is intriguing that an operon regulated by AI-2 encodes functions resembling the ribose transporter, given recent findings that AI-2 is derived from the ribosyl moiety of S-ribosylhomocysteine.
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Taga
authors.forename: J L
authors.initials: JL
authors.lastname: Semmelhack
authors.forename: B L
authors.initials: BL
authors.lastname: Bassler
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D013437:Carbon-Sulfur Lyases; D015964:Gene Expression Regulation, Bacterial; D009876:Operon; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C085427:LuxI protein, Bacteria; D014157:Transcription Factors; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria