Abstract
The Bacillus subtilis σW regulon is induced by different stresses that most probably affect integrity of the cell envelope. The activity of the extracytoplasmic function (ECF) sigma factor σW is modulated by the transmembrane anti-sigma factor RsiW, which undergoes stress-induced degradation in a process known as regulated intramembrane proteolysis, finally resulting in the release of σW and the transcription of σW-controlled genes. Mutations in the ecsA gene, which encodes an ATP binding cassette (ABC) of an ABC transporter of unknown function, block site-2 proteolysis of RsiW by the intramembrane cleaving protease RasP (YluC). In addition, degradation of the cell division protein FtsL, which represents a second RasP substrate, is blocked in an ecsA-negative strain. The defect in σW induction of an ecsA-knockout strain could be partly suppressed by overproducing RasP. A B. subtilis rasP-knockout strain displayed the same pleiotropic phenotype as an ecsA knockout, namely defects in processing α-amylase, in competence development, and in formation of multicellular structures known as biofilms.