AMINO-ACYLATION SITE MUTATIONS IN AMINO ACID-ACTIVATING DOMAINS OF SURFACTIN SYNTHETASE - EFFECTS ON SURFACTIN PRODUCTION AND COMPETENCE DEVELOPMENT IN BACILLUS-SUBTILIS

The part of the srfA operon of Bacillus subtilis that contains the reg ion required for competence development is composed of the first four amino acid-activating domains which are responsible for the incorporat ion of Glu, Leu, D-Leu, and Val into the peptide moiety of the lipopep tide surfactin. Ser-to-Ala substitutions were made in the amino-acylat ion site of each domain, and their effects on surfactin production and competence development were examined. All of the mutations conferred a surfactin-negative phenotype, supporting the finding that the conser ved Ser in the amino-acylation site is required for peptide synthesis. However, none of the mutations affected significantly competence deve lopment or the expression of a lacZ fusion to the late competence oper on comG. This, coupled with recent findings that only the fourth, Val- activating, domain is required for competence, suggests that some acti vity, other than amino-acylation and perhaps unrelated to peptide synt hesis, possessed by the fourth domain is involved in the role of srfA in regulating competence development.