title: A quorum-sensing system in the free-living photosynthetic bacterium Rhodobacter sphaeroides.
abstract: Rhodobacter sphaeroides is a free-living, photoheterotrophic bacterium known for its genomic and metabolic complexity. We have discovered that this purple photosynthetic organism possesses a quorum-sensing system. Quorum sensing occurs in a number of eukaryotic host-associated gram-negative bacteria. In these bacteria there are two genes required for quorum sensing, the luxR and luxI homologs, and there is an acylhomoserine lactone signal molecule synthesized by the product of the luxI homolog. In R. sphaeroides, synthesis of a novel homoserine lactone signal, 7,8-cis-N-(tetradecenoyl)homoserine lactone, is directed by a luxI homolog termed cerI. Two open reading frames immediately upstream of cerI are proposed to be components of the quorum-sensing system. The first of these is a luxR homolog termed cerR, and the second is a small open reading frame of 159 bp. Inactivation of cerI in R. sphaeroides results in mucoid colony formation on agar and formation of large aggregates of cells in liquid cultures. Clumping of CerI mutants in liquid culture is reversible upon addition of the acylhomoserine lactone signal and represents a phenotype unlike those controlled by quorum sensing in other bacteria.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston 77224, USA.
authors.forename: A
authors.initials: A
authors.lastname: Puskas
authors.forename: E P
authors.initials: EP
authors.lastname: Greenberg
authors.forename: S
authors.initials: S
authors.lastname: Kaplan
authors.forename: A L
authors.initials: AL
authors.lastname: Schaefer
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002450:Cell Communication / Q000235:genetics*; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010675:Pheromones / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D012097:Repressor Proteins; D015183:Restriction Mapping; D012242:Rhodobacter sphaeroides / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; C085427:LuxI protein, Bacteria; C109408:N-(7-tetradecenoyl)homoserine lactone; D010675:Pheromones; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C064778:LuxR autoinducer binding proteins; D015107:4-Butyrolactone