SRFA IS AN OPERON REQUIRED FOR SURFACTIN PRODUCTION, COMPETENCE DEVELOPMENT, AND EFFICIENT SPORULATION IN BACILLUS-SUBTILIS

The srfA locus of Bacillus subtilis is defined by a transposon Tn917 insertion and is required for production of the peptide secondary metabolite surfactin. The srfA locus was isolated by cloning the DNA flanking srfA::Tn917 insertions followed by chromosome walking. The cloned region is an operon of over 25 kb which covers the transcription initiation region but not the intact 3' end of srfA. csh-293, which was previously identified as a Tn917lac mutation that impairs competence development and causes a conditional defect in sporulation, was known to be located in the vicinity of the srfA locus within the B. subtilis genome. The csh-293::Tn917lac mutation was discovered to cause a defect in surfactin production and was shown to be located in the srfA operon by its cotransformation with srfA mutations and by Southern hybridization analysis. Insertion mutations in srfA, created by the chromosomal integration of plasmids bearing overlapping srfA DNA fragments, were examined for their effects on surfactin production, competence, and sporulation. All three processes were found to require the intact 5' half of the srfA operon, whereas the 3' half of srfA was found to be required for sporulation and surfactin production but not competence. These experiments show that srfA gene products function in B. subtilis cell specilization and differentiation.