title: gerR, a novel ger operon involved in L-alanine- and inosine-initiated germination of Bacillus cereus ATCC 14579.
abstract: Bacillus cereus endospores germinate in response to particular nutrients. Spores are able to sense these nutrients in the environment by receptors encoded by the gerA family of operons. Analysis of the Bacillus cereus ATCC 14579 genome revealed seven gerA family homologues. Using a transposon Tn917-based insertional mutagenesis approach followed by an enrichment procedure to select for l-alanine-induced germination mutants, we isolated a mutant with a defect in the l-alanine germination pathway. The transposon disrupted the last gene of a tricistronic gerA family operon, designated gerR, with the order gerRA, gerRC, gerRB. A second mutant was created by insertion of pMUTIN4 in gerRC. Both mutants showed the same phenotype for nutrient-induced germination. Spores of the gerR mutant strains were blocked in their l-alanine-initiated germination pathway and showed a delayed inosine-induced germination response. Apparently, germination mediated by l-alanine and inosine cannot be compensated for completely by the other germinant receptors, and this points towards an essential role of the gerR-encoded receptor in the receptor complex. In food products, spores of the mutant strains showed a reduced germination response compared to spores of the parental strain. High-pressure-initiated germination was not affected by the gerR mutations, as experiments with 100 and 550 MPa showed no difference with spores of the parental strain.
authors.affiliation: Wageningen Centre for Food Sciences, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Luc.Hornstra@wur.nl
authors.forename: Luc M
authors.initials: LM
authors.lastname: Hornstra
authors.forename: Ynte P
authors.initials: YP
authors.lastname: de Vries
authors.forename: Willem M
authors.initials: WM
authors.lastname: de Vos
authors.forename: Tjakko
authors.initials: T
authors.lastname: Abee
authors.forename: Marjon H J
authors.initials: MH
authors.lastname: Wells-Bennik
mesh_terms: D000409:Alanine / Q000494:pharmacology*; D000818:Animals; D001409:Bacillus cereus / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D006874:Hydrostatic Pressure; D007288:Inosine / Q000494:pharmacology*; D008461:Meat Products / Q000382:microbiology; D016254:Mutagenesis, Insertional; D009876:Operon; D012275:Oryza / Q000382:microbiology; D013171:Spores, Bacterial / Q000187:drug effects / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D007288:Inosine; D000409:Alanine