Global analysis of the general stress response of Bacillus subtilis

Gene arrays containing all currently known open reading frames of Bacillus subtilis were used to examine the general stress response of Bacillus. By p roteomics, transcriptional analysis, transposon mutagenesis, and consensus promoter-based screening, 75 genes had previously been described as sigma ( B)-dependent general stress genes. The present gene array-based analysis co nfirmed 62 of these already known general stress genes and detected 63 addi tional genes subject to control by the stress sigma factor sigma (B). At le ast 24 of these 125 UR-dependent genes seemed to be subject to a second, si gma (B)-independent stress induction mechanism. Therefore, this transcripti onal profiling revealed almost four times as many regulon members as the pr oteomic approach, but failure of confirmation of all known members of the s igma (B) regulon indicates that even this approach has not yet elucidated t he entire regulon. Most of the sigma (B)-dependent general stress proteins are probably located in the cytoplasm, but 25 contain at least one membrane -spanning domain, and at least 6 proteins appear to be secreted. The functi ons of most of the newly described genes are still unknown. However, their classification as sigma (B)-dependent stress genes argues that their produc ts most likely perform functions in stress management and help to provide t he nongrowing cell with multiple stress resistance. A comprehensive screeni ng program analyzing the multiple stress resistance of mutants with mutatio ns in single stress genes is in progress. The first results of this program , showing the diminished salt resistance of yjbC and yjbD mutants compared to that of the wild type, are presented. Only a few new sigma (B)-dependent proteins with already known functions were found, among them SodA, encodin g a superoxide dismutase. In addition to analysis of the sigma (B)-dependen t general stress regulon, a comprehensive list of genes induced by heat, sa lt, or ethanol stress in a sigma (B)-independent manner is presented. Perha ps the most interesting of the sigma (B)-independent stress phenomena was t he induction of the extracytoplasmic function sigma factor sigma (W) and it s entire regulon by salt shock.