Résumé
The mechanisms involved in the ability of B. cereus to multiply at low temperature were investigated. It was assumed that many genes involved in cold acclimation would be up-regulated at low temperature. Recombinase-based in vivo expression technology (IVET) was adapted to the detection of the transient activation of B. cereus promoters during growth at 10 °C. Four independent screenings of a promoter library from type strain ATCC 14579 were performed and 17 clones were isolated. They corresponded to 17 promoter regions that displayed a reproducible elevated expression at 10 °C relative to 30 °C. This analysis revealed several genes that may be important for B. cereus to grow successfully in the restrictive conditions of cold habitats. Among them, a locus corresponding to open reading frames BC5402 to BC5398 harbouring a lipase encoding gene and a putative transcriptional regulator was identified three times. While a mutation in the putative regulator encoding gene did not cause any particular phenotype, a mutant deficient for the lipase encoding gene showed reduced growth abilities at low temperature compared with the parental strain. The mutant did not change its fatty acid profiles in the same way as the wild-type when grown at 12 °C instead of 37 °C. This study demonstrates the feasibility of a promoter trap strategy for identifying cold induced genes. It outlines a first picture of the different processes involved in B. cereus cold acclimation