title: The PlcR virulence regulon of Bacillus cereus.
abstract: PlcR is a Bacillus cereus transcriptional regulator, which activates gene expression by binding to a nucleotidic sequence called the 'PlcR box'. To build a list of all genes included in the PlcR regulon, a consensus sequence was identified by directed mutagenesis. The reference strain ATCC14579 sequenced genome was searched for occurrences of this consensus sequence to produce a virtual regulon. PlcR control of these genes was confirmed by comparing gene expression in the reference strain and its isogenic Delta-plcR strain using DNA microarrays, lacZ fusions and proteomics methods. The resulting list included 45 genes controlled by 28 PlcR boxes. Forty of the PlcR controlled proteins were exported, of which 22 were secreted in the extracellular medium and 18 were bound or attached to cell wall structures (membrane or peptidoglycan layer). The functions of these proteins were related to food supply (phospholipases, proteases, toxins), cell protection (bacteriocins, toxins, transporters, cell wall biogenesis) and environment-sensing (two-component sensors, chemotaxis proteins, GGDEF family regulators). Four genes coded for cytoplasmic regulators. The PlcR regulon appears to integrate a large range of environmental signals, including food deprivation and self cell-density, and regulate the transcription of genes designed to overcome obstacles that hinder B. cereus growth within the host: food supply, host barriers, host immune defenses, and competition with other bacterial species. PlcR appears to be a key component in the efficient adaptation of B. cereus to its host environment.
authors.affiliation: INRA, Génétique microbienne et Environnement, Guyancourt, France. michel.gohar@ jouy.inra.fr
authors.forename: Michel
authors.initials: M
authors.lastname: Gohar
authors.forename: Karoline
authors.initials: K
authors.lastname: Faegri
authors.forename: Stéphane
authors.initials: S
authors.lastname: Perchat
authors.forename: Solveig
authors.initials: S
authors.lastname: Ravnum
authors.forename: Ole Andreas
authors.initials: OA
authors.lastname: Økstad
authors.forename: Myriam
authors.initials: M
authors.lastname: Gominet
authors.forename: Anne-Brit
authors.initials: AB
authors.lastname: Kolstø
authors.forename: Didier
authors.initials: D
authors.lastname: Lereclus
mesh_terms: D001409:Bacillus cereus / Q000235:genetics* / Q000472:pathogenicity*; D001426:Bacterial Proteins / Q000235:genetics*; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007107:Immune System; D007763:Lac Operon; D008954:Models, Biological; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D009711:Nucleotides / Q000737:chemistry; D020411:Oligonucleotide Array Sequence Analysis; D040901:Proteomics / Q000379:methods; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D009711:Nucleotides; C099480:PlcR protein, Bacillus; D015534:Trans-Activators