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Summary: The Bacillus subtilis sigW gene encodes an extracytoplasmic function (ECF) [sigma] 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 (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 [sigma]W activates a large stationary-phase regulon that functions in detoxification, production of antimicrobial compounds or both.

(C) 1999 Blackwell Science Ltd.