Genes of the sbo-alb locus of Bacillus subtilis are required for production of the antilisterial bacteriocin subtilosin.

Abstract

Bacillus subtilis JH642 and a wild strain of B. subtilis called 22a both produce an antilisterial peptide that can be purified by anion-exchange and gel filtration chromatography. Amino acid analysis confirmed that the substance was the cyclic bacteriocin subtilosin. A mutant defective in production of the substance was isolated from a plasmid gene disruption library. The plasmid insertion conferring the antilisterial-peptide-negative phenotype was located in a seven-gene operon (alb, for antilisterial bacteriocin) residing immediately downstream from the sbo gene, which encodes the precursor of subtilosin. An insertion mutation in the sbo gene also conferred loss of antilisterial activity. Comparison of the presubtilosin and mature subtilosin sequences suggested that certain residues undergo unusual posttranslational modifications unlike those occurring during the synthesis of class I (lantibiotic) or some class II bacteriocins. The putative products of the genes of the operon identified show similarities to peptidases and transport proteins that may function in processing and export. Two alb gene products resemble proteins that function in pyrroloquinoline quinone biosynthesis. The use of lacZ-alb and lacZ-sbo gene fusions, along with primer extension analysis, revealed that the sbo-alb genes are transcribed from a major promoter, residing upstream of sbo, that is very likely utilized by the sigma(A) form of RNA polymerase. The sbo and alb genes are negatively regulated by the global transition state regulator AbrB and are also under positive autoregulation that is not mediated by the subtilosin peptide but instead requires one or more of the alb gene products.