CHARACTERIZATION OF NEWLY ISOLATED BACILLUS-SUBTILIS C1 WHICH IS SENSITIVE TO ANTIBIOTIC PRODUCED BY LACTIC-ACID COCCUS

An aerobic, Gram-positive endospore-forming rod, strain Cl, was isolated from a contaminated culture of Lactococcus lactis IO-1. Strain C1 was more sensitive to nisin and the peptide antibiotic produced by strain IO-1 than Bacillus subtilis JCM 1465T. Strain C1 was significantly different from B. subtilis JCM 1465T in that it produced a black pigment. Conventional identification techniques did not give enough information to determine the taxonomic position of strain Cl. DNA-DNA hybridization revealed that the homology value between strain C1 and JCM 1465T was as high as 94% under optimal conditions. Thus, strain C1 was identified as a strain of B. subtilis. It was demonstrated that strain C1 was an effective indicator strain for the bioassay of antibiotics produced by lactic acid cocci.