Induction of accelerated sporangial lysis by basic peptide antibiotics. A novel method of preparation of free spores of bacilli.

Abstract

An accelerated release of free spores from sporangia of Bacillus cereus NCIB‐8122 and Bacillus subtilis SMYW was induced by the addition of the basic peptide antibiotics, polymyxin B or colistin (100 μg/ml), to sporangia formed in liquid Bactopeptone medium. Destruction of sporangial cell walls of B. cereus prelabelled with 3H‐4‐diaminopimelic acid commenced shortly after the addition of either antibiotic, the label being gradually released into the medium. Normal free spores were released following the addition of antibiotics to sporangia containing refractile spores (stages IV‐V of sporogenesis). Earlier additions induced the lysis of both compartments of the sporangium, accompanied by the release of already‐synthesized dipicolinic acid and alreadyaccumulated 45calcium. The heat resistance and germination ability of spores released in the presence of the antibiotics were the same as those of control spores released by long‐term spontaneous lysis of sporangia. Similar effects of the antibiotics were observed with B. subtilis SMYW. Results obtained were used firstly for fast preparation of relatively clean free spores and secondly for the characterization of the developmental stage of sporogenesis at which the spore becomes independent of the maternal cell. It reaches this property at the end of stage IV and during stage V.