Jackson W. Foster

ANTIBIOTIC SUBSTANCES PRODUCED BY BACTERIA

In 1877, Pasteur1 reported that laboratory animals, injected with the causative agent of anthrax (Bacillus anthracis) and common saprophytic bacteria, failed to develop the disease. This effect was ascribed to oxygen-starvation of the anthrax organism, brought about by utilization of oxygen by the saprophyte. During the years that followed, the inhibitory action was found to be associated with many mixed cultures and has come to be known as microbial antagonism. We now know that antagonisms, in the majority of cases, may be charged to the production by one microorganism of metabolic products which have toxic or inhibitory activity for other microorganisms. Such chemical identities have come to be known as antibiotics. As is often the case with scientific studies, chance observation led to the study of many antibiotics. Thus, Emmerich,2 during a demonstration before his class, accidentally discovered that a guinea pig that had been previously injected with a culture of Streptococcus erysipelatis did not develop cholera when inoculated with Vibrio cholerae. This was followed closely by Bouchard’s3 observation that rabbits, previously inoculated with Bacillus anthracis, did not develop anthrax when small amounts of cultures of Pseudomoms aeruginosa were injected, a finding that was later extended to include sterilized Pseudomonas aeruginosa cultures. The mass of literature, often conflicting, that has accumulated concerning these antagonistic activities, leads one to realize that only through the chemical isolation of the antibiotics concerned is it possible to completely understand the antagonistic phenomena. In the case of Pseudomoms aeruginosa antagonisms, the activity has been variously ascribed to enzymes, fatty acids, surface tension depressants, pigments, etc. In the 67 years since this type of antagonism was first noticed, no less than two phenazine derivatives, with their structure confirmed by synthesis, and five crystalline compounds of unknown structure, all with antibiotic activity, have been isolated from this one organism. Is it any wonder that different investigators, working with different strains of this organism and different media, have reported conflicting results? Returning to the discovery of antagonistic bacteria, four conditions have furthered their investigation. The first of these is chance, which