Taxonomic principles in the actinomycetes.

Problems in the systematics and classification of actinomycetes have attracted many investigators in recent years. Increased interest in the actinomycetes is due to the need for delineating specific antagonistic microorganisms and exploring them as a source of new, desirable antibiotics. As everywhere in biology, the most difficult and complicated, but at the same time most important, aspect of the study of organisms is the identification of species. Without prejudging the question "what is a species?" it is important to know in everyday laboratory work "what are the criteria for species and which methods best reveal them?" This question is solved variously by different authors. Some suggest cultural characteristics, such as pigmentation, appearance of colonies, etc., as a basis for species differentiation (Baldacci et al., 1954); others prefer physiological properties, the ability to assimilate certain carbon sources (Kurosawa, 1948; Benedict et al. 1955; Zahner and Ettlinger, 1957), or nitrogen sources (Okami, 1952; Burkholder et al., 1954). Some authors suggest utilizing actinophage specificity (Ludwig and Hutchinson, 1949; Hata et al., 1953) in the differentiation of actinomycete species. Waksman and Lechevalier and Wakman (1957) use physiological and cultural characteristics. Also attempts are being made to differentiate actinomycetes on the basis of chemical structure of cell walls (Cummins and Harris, 1958; Romano and Sohler, 1956) or on the formation of different protuberances on the surface of spores (Flaig and Kuitzner, 1958). One characteristic alone, whatever it be, is inadequate for the recognition and especially for the identification of a species. Only the sum of properties can characterize and differentiate a species. The more detailed and comprehensive the study of an organism, the sharper are species boundaries and hence the more exact its identification. In our work on the systematics of micro-