INRA, UMR408, Site Agroparc, 84914 Avignon Cedex 9, France.
Appl Environ Microbiol. 2010 Apr;76(8):2562-73. doi: 10.1128/AEM.02348-09. Epub 2010 Feb 26.
The mechanisms involved in the ability of Bacillus cereus to multiply at low temperatures were investigated. It was assumed that many genes involved in cold acclimation would be upregulated at low temperatures. Recombinase-based in vivo expression technology (IVET) was adapted to the detection of the transient activation of B. cereus promoters during growth at 10 degrees 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 reproducibly elevated expression at 10 degrees C relative to expression at 30 degrees C. This analysis revealed several genes that may be important for B. cereus to grow successfully under the restrictive conditions of cold habitats. Among them, a locus corresponding to open reading frames BC5402 to BC5398, harboring 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 in the lipase-encoding gene showed reduced growth abilities at low temperatures 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 degrees C instead of 37 degrees 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.
研究了蜡状芽孢杆菌在低温下繁殖能力的相关机制。假设许多与冷适应相关的基因在低温下会被上调。基于重组酶的体内表达技术(IVET)被用于检测在 10°C 生长过程中 B. cereus 启动子的瞬时激活。对来自模式菌株 ATCC 14579 的启动子文库进行了四次独立筛选,分离出 17 个克隆。它们对应于 17 个启动子区域,与 30°C 时的表达相比,在 10°C 时表现出可重复的表达升高。该分析揭示了几个可能对 B. cereus 在寒冷栖息地的限制条件下成功生长很重要的基因。其中,对应于开放阅读框 BC5402 到 BC5398 的一个基因座,携带一个脂肪酶编码基因和一个假定的转录调节因子,被鉴定了三次。虽然假定调节因子编码基因的突变没有引起任何特殊表型,但与亲本菌株相比,缺失脂肪酶编码基因的突变体在低温下的生长能力降低。与野生型相比,突变体在以 12°C 而不是 37°C 生长时,其脂肪酸谱没有以相同的方式发生变化。本研究证明了利用启动子陷阱策略识别冷诱导基因的可行性。它概述了 B. cereus 冷适应中涉及的不同过程的初步情况。