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

Bacillus subtilis JH642 and a wild strain of B. subtilis called 22a both pr oduce an antilisterial peptide that can be purified by anion-exchange and g el filtration chromatography. Amino acid analysis confirmed that the substa nce 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 w as located in a seven-gene operon (alb, for antilisterial bacteriocin) resi ding 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 subtilo sin sequences suggested that certain residues undergo unusual posttranslati onal modifications unlike those occurring during the synthesis of class I ( lantibiotic) or some class II bacteriocins. The putative products of the ge nes 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. T he use of lacZ-alb and lacZ-sbo gene fusions, along with primer extension a nalysis, revealed that the sbo-alb genes are transcribed from a major promo ter, 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 auto regulation that is not mediated by the subtilosin peptide but instead requi res one or more of the alb gene products.