Strain Specificity and Production of Antibiotic Substances

Abstract

The ability of organisms belonging to different species or even different genera to produce the same'antibiotic has been definitely established for the fungi.This is true of penicillin production by different species of Penicillium and Aspergillus; of clavacin, produced by a variety of species belonging to these two as well as other genera; of citrinin; and of other antibiotics.In the case of spore-forming bacteria, which received con- siderable attention during the last few years, the problem is more difficult because of the greater complexity of the substances produced.It is diffi- cult to say as yet whether some of the products described in the literature, such as subtilin and bacitracin, are chemical individuals or mixtures.Likewise it is difficult to say whether such mixtures may contain one or more of the recognizably pure substances such as gramicidin, tyrocidine, or gramicidin S along with other active and inactive polypeptides; tyrothri- cin, for example, has been shown to contain gramicidin and tyrocidine, along with other less well-defined substances.The identity of an antibiotic produced by different species of actino- mycetes is complicated by the difficulty of recognizing distinct species.It is believed, however, that the data presented in this paper tend to suggest that different species, or at least what may be considered as such, may pro- duce the same type of antibiotic.The differences in yield and especially in the impurities accompanying the particular antibiotic tend to emphasize further the differences in species, or at least in strain specificity.In 1940, the isolation from the soil of an actinomyces that had strong antibiotic properties was reported.This substance was designated as *actinomycin and the organism described as A ctinomyces (Streptomyces) antibioticus.'Since then some 10,000 cultures of actinomycetes have been isolated from soils, composts, and other substrates, and tested for anti-