In Bacillus subtilis, two extracellular signaling peptides, ComX pheromone and CSF (competence and sporulation factor), stimulate the development of genetic competence and surfaction biosynthesis in response to high cell density (quorum sensing) by regulating the activity of transcription factor ComA. We recently showed that biosynthesis of dipeptide antibiotic bacilysin is linked to ComA and PhrC(CSF) in a Spo0K(Opp)-dependent manner by constructing phrC-, comA- and oppA-disrupted mutants of B. subtilis. In the present study, another pathway of quorum-sensing global regulation, namely, ComQ/ComX was found to be essential for bacilysin biosynthesis. Comp function in this chain was dispensable, most probably because of the existence of an alternative mean of ComA activation. The disruption of srfA operon in the bacilysin producer resulted with the bacilysin-negative phenotype; thus, our study verified that the srfA operon functions directly in the production of bacilysin. The abrB mutation suppressed the bacilysin-negative phenotype of a spo0A mutant, whereas the same mutation in the wild-type strain resulted in a significant increase in the production of bacilysin. This indicated that abrB gene product negatively controls the transcription of the gene(s) involved in bacilysin formation. (C) 2003 Elsevier Science B.V. All rights reserved.