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