Polypeptide antibiotic 26a from Bacillus subtilis. I. Taxonomy and fermentative production

In surface cultures on NK/2-Sym's medium, the isolate No. 26a of Bacillus subtilis from the intestinal tract of Galleria mellonella larvae produced three antibacterial substances which were separated by gel filtration on Sephadex G-25 column. The major bioactive compound named 26a had a close resemblance to bacitracin family of polypeptide antibiotics. Two minor active compounds, i.e. a bacteriolytic enzyme with endo-beta-N-acetylmuramidglycanohydrolase (EC. 3. 2. 1. 17) activity and other unidentified factor were usually synthetized in trace amounts. Maximum yield of 26a generally occurred after 120 hour incubation, when the producer reached the stationary growth phase and general sporulation of the bacterial cultures was found. The basal medium of NK/2-Sym supplemented by addition of manganese ions (10(-4) M), d-glucose (1%) and inorganic nitrogen beneficially resulted in antibiotic potency of the fermentation broth. The antibiotics produced by other isolates (Nos 5AK, 15 and 92) have been also analyzed and from their properties they can be tentatively classified as members of bacitracin group polypeptides. A possible role of the antibiotics produced by intestinal Bacillus spp in the formation process of typical gut microflora of G. mellonella is discussed.