Identification of a genetic locus required for biosynthesis of the lipopeptide antibiotic surfactin in Bacillus subtilis

Surfactin is a lipopeptide antibiotic produced by the cells of Bacillus subtilis ATCC 21332. A genetic locus responsible for surfactin production (sfp) was transferred by transformation from ATCC 21332 to JH642, a derivative of the standard B. subtilis 168. To study the sfp locus at the molecular level, a Tn917 insertion mutant that was blocked in surfactin production (srf) was isolated. The srf:Tn917 mutation was found to be closely linked to sfp, and both loci mapped by PBS1 phage transduction to the chromosomal region between arol and mtlB. These studies suggest that JH642, a strain which is not a producer of surfactin (genotypically sfp⁰), contains at least some of the genes encoding surfactin production. Expression of the srf gene(s) was examined in both sfp and sfp⁰ cells by assaying β-galactosidase activity encoded by a promoterless lacZ gene that was fused to the srf::Tn917 insertion. In cells of both strains, srf-directed β-galactosidase activity increased when cells entered the stationary phase of the growth curve, but the activity in sfp cells was higher than that in sfp⁰ cells. srf-lacZ expression was partially impaired by a mutation in spo0A. In sfp⁰ cells, this dependence on the spo0A gene product could be entirely bypassed by an abrB suppressor mutation. In the sfp cells, the abrB mutation could not restore the defect conferred by the spo0A mutation. These data suggest that the sfp locus, which is responsible for surfactin production, alters the transcriptional regulation of srf in JH642 cells.