gerR , a Novel ger Operon Involved in l -Alanine- and Inosine-Initiated Germination of Bacillus cereus ATCC 14579

Author:

Hornstra Luc M.12,de Vries Ynte P.123,de Vos Willem M.1,Abee Tjakko13,Wells-Bennik Marjon H. J.12

Affiliation:

1. Wageningen Centre for Food Sciences

2. Agrotechnology and Food Innovations

3. Laboratory of Food Microbiology, Wageningen University, Wageningen, The Netherlands

Abstract

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 Tn 917 -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.

Publisher

American Society for Microbiology

Subject

Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology

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