Identification of target promoters for the Bacillus subtilis extracytoplasmic function σ factor, σW

The Bacillus subtilis sigW gene encodes an extracytoplasmic function (ECF) a factor that is expressed in early stationary phase from a sigW-dependent autoregulatory promoter, Pw. Using a consensus-based search procedure, we have identified 15 operons preceded by promoters similar in sequence to Pw, At least 14 of these promoters are dependent on sigma(W) both in vivo and in vitro as judged by lacZ reporter fusions, run-off transcription assays and nucleotide resolution start site mapping, We conclude that sigma(W) controls a regulon of more than 30 genes, many of which encode membrane proteins of unknown function. The sigma(W) regulon includes a penicillin binding protein (PBP4*) and a co-transcribed amino acid racemase (RacX), homologues of signal peptide peptidase (Ytel), flotillin (YuaG), ABC transporters (YknXYZ), non-haembromoperoxidase (YdjP), epoxide hydrolase (YfhM) and three small peptides with structural similarities to bacteriocin precursor polypeptides. We suggest that sigma(W) activates a large stationary-phase regulon that functions in detoxification, production of antimicrobial compounds or both.