THE PRODUCTION OF BACTERICIDAL SUBSTANCES BY AEROBIC SPORULATING BACILLI

Abstract

Several spp. of aerobic sporulating bacilli recently isolated from soil, sewage, manure, and cheese, as well as authentic strains obtained from type culture collections, exhibit antagonistic activity against unrelated microorganisms. Cultures of these aerobic sporulating bacilli yield an alcohol-soluble, water-insoluble fraction, [long dash]tyrothricin,[long dash]which is bactericidal for most Gram-positive and Gram-negative microbial species. Two crystalline products have been separated from tyrothricin: one, tyro-cidine, is bactericidal in vitro for both Gram-positive and Gram-negative spp.; the other, gramicidin, is effective only against Gram-positive microorganisms. In general, tyro-cidine behaves like a protoplasmic poison and like other antiseptics, loses much of its activity in the presence of animal tissues; gramicidin exerts a much more subtle physiological effect on the susceptible bacterial cells and. when applied locally at the site of the infection, retains in vivo a striking activity against Gram-positive microorganisms.