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


John D. Helmann. E-mail; Tel. (607) 255 6570; Fax (607) 255 3904.


The Bacillus subtilis sigW gene encodes an extracytoplasmic function (ECF) σ 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 σW 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 σW controls a regulon of more than 30 genes, many of which encode membrane proteins of unknown function. The σW regulon includes a penicillin binding protein (PBP4*) and a co-transcribed amino acid racemase (RacX), homologues of signal peptide peptidase (YteI), flotillin (YuaG), ABC transporters (YknXYZ), non-haem bromoperoxidase (YdjP), epoxide hydrolase (YfhM) and three small peptides with structural similarities to bacteriocin precursor polypeptides. We suggest that σW activates a large stationary-phase regulon that functions in detoxification, production of antimicrobial compounds or both.