Two genes from Bacillus subtilis under the sole control of the general stress transcription factor σB

Abstract

The general stress response of Bacillus subtilis is triggered by a variety of environmental and metabolic stresses which activate the aB transcription factor. Among the more than 100 genes controlled b y aB.(the csb genes), the functions identified thus far include resistance to oxidative stress, resistance to protein denaturation and resistance to osmotic stress. T o understand the breadth of functions in which csb genes participate, the transcriptional organization and predicted products of two such genes previously identified in a screen for oB-dependent lacZ fusions were analysed. The csb-22::Tn917lacZ and csb-34::Tn917lacZ fusions are unusual among csb genes in that their expression appears to be completely dependent upon aB. By plasmidintegration experiments, fusion analyses and site-directed mutagenesis, stressinducible, aB-dependent promoters for both these fusions were identified. The csb-34 fusion marked an ORF (yxcC or csbC) which by sequence analysis lay in a monocistronic transcriptional unit. This ORF encoded a predicted 461-residue product which had high identity with Class I sugar transporters of the major facilitator superfamily. It was speculated that the csbC product could serve either a nutritional or an osmotic protection function. In contrast, the csb-22 fusion identified an ORF (ywmG or csbD) which appeared to be the second gene of a two-gene operon. This ORF encoded a predicted 62-residue product which resembled a small Escherichia coli protein of unknown function. The aBdependent promoter lay immediately upstream from csbD and appeared to be an internal promoter for the operon.

Characterization of the ς B Regulon in Staphylococcus aureus

“…However, particularly in response to heat shock, the B -dependent promoter seemed to be the strongest one in all of the cases tested so far. This complex regulation was also described for many B -dependent proteins in B. subtilis (2,19,31,55). Only csb7, csb9, and csb16 seem to be transcribed solely by B under the conditions tested so far.…”

RpoS-Regulated Genes ofEscherichia coliIdentified by RandomlacZFusion Mutagenesis

“…The yjbJ gene has a very high RpoS dependence in stationary phase, especially when grown in minimal media (Table 2), and is one of the most abundant proteins produced in stationary phase (48). Moreover, this gene has homology similarities to csbD of Bacillus subtilis, which is also regulated by a stress sigma factor (1). Some of the RpoSdependent genes of this class have recently been shown to be upregulated under different growth conditions.…”

Regulation of Transcription of Compatible Solute Transporters by the General Stress Sigma Factor, σB, inListeria monocytogenes

“…This finding is particularly interesting, since a majority of stress response genes are typically under control of dual promoters to sustain flexible transcription under all conditions, particularly for those genes that are essential (25). Only a few genes, in fact, are known to rely solely upon B for their transcription (1,21,24). The dependence of opuC on B provides a mechanism for preferential use of betaine to maintain osmotic balance under normal growth conditions, since B activity is minimal under those conditions.…”