Peptide Antibiotics and Sporulation: Induction of Sporulation in Asporogenous and Peptide-negative Mutants of Bacillus brevis

Abstract

Mutants of B. brevis ATCC 8185 were isolated which were unable to produce detectable amounts of tyrocidine and/or linear gramicidin peptide antibiotics. Tyrocidine-negative mutants (BM5, BM21, BM44) sporulated normally. Gramicidin-negative mutants (BM2, BM24) were oligosporogenous and mutants unable to produce either peptide (S18, S19) were asporogenous. Addition of tyrocidine and/or gramicidin to asporogenous mutants in rich medium did not stimulate sporulation. These mutants formed normal spores after being transferred to N-free medium and upon the addition of tyrocidine. Nutrient broth had a suppressive effect on tyrocidine-induced sporulation of S18. The tyrocidine-negative mutant BM44, sporogenous in rich medium, could sporulate under N deprivation only if supplemented with tyrocidine. The significance of the peptide antibiotics for a regulatory role in sporogenesis of B. brevis is discussed.