title: The agr radiation: an early event in the evolution of staphylococci.
abstract: Agr is a global regulatory system in the staphylococci, operating by a classical two-component signaling module and controlling the expression of most of the genes encoding extracellular virulence factors. As it is autoinduced by a peptide, encoded within the locus, that is the ligand for the signal receptor, it is a sensor of population density or a quorum sensor and is the only known quorum-sensing system in the genus. agr is conserved throughout the staphylococci but has diverged along lines that appear to parallel speciation and subspeciation within the genus. This divergence has given rise to a novel type of interstrain and interspecies cross-inhibition that represents a fundamental aspect of the organism's biology and may be a predominant feature of the evolutionary forces that have driven it. We present evidence, using a newly developed, luciferase-based agr typing scheme, that the evolutionary divergence of the agr system was an early event in the evolution of the staphylococci and long preceded the development of the nucleotide polymorphisms presently used for genotyping. These polymorphisms developed, for the most part, within different agr groups; mobile genetic elements appear also to have diffused recently and, with a few notable exceptions, have come to reside largely indiscriminately within the several agr groups.
authors.affiliation: Molecular Pathogenesis Program and Department of Microbiology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Ave., New York, NY 10016, USA.
authors.forename: Jesse S
authors.initials: JS
authors.lastname: Wright
authors.forename: Katrina E
authors.initials: KE
authors.lastname: Traber
authors.forename: Rebecca
authors.initials: R
authors.lastname: Corrigan
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Benson
authors.forename: James M
authors.initials: JM
authors.lastname: Musser
authors.forename: Richard P
authors.initials: RP
authors.lastname: Novick
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D005838:Genotype; D006460:Hemolysin Proteins / Q000378:metabolism; D006461:Hemolysis; D008156:Luciferases / Q000235:genetics; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000502:physiology; D013211:Staphylococcus aureus / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D015534:Trans-Activators; D008156:Luciferases