Antibiotics that inhibit cell wall biosynthesis induce expression of the Bacillus subtilis σW and σM regulons

Bacillus subtilis encodes seven extracytoplasmic function (ECF) sigma factors. The sigma (W) regulon includes functions involved in detoxification and protection against antimicrobials, whereas sigma (M) is essential for growth at high salt concentrations. We now report that antibiotics that inhibit cell wall biosynthesis induce both sigma (W) and sigma (M) regulons as monitored using DNA microarrays. Induction of selected sigma (W)-dependent genes was confirmed using lacZ reporter fusions and Northern blot analysis. The ability of vancomycin to induce the sigma (W) regulon is dependent on both sigma (W) and the cognate anti-sigma, RsiW, but is independent of the transition state regulator AbrB. These results suggest that the membrane-localized RsiW anti sigma(W) factor mediates the transcriptional response to cell wall stress. Our findings are consistent with the idea that one function of ECF sigma factors is to coordinate antibiosis stress responses and cell envelope homeostasis.