Studies on the Cell-Wall Composition and Taxonomy of Actinomycetales and Related Groups

SUMMARY: The cell-wall compositions of 51 strains of Actinomyces, Nocardia, Streptomyces, Micromonospora, Mycobacterium and Propionibacterium have been investigated, together with those of 7 strains of Eumycetes. The cell walls of the actinomycetes were made up of sugars, amino sugars and amino acids (the latter few in number). The general pattern of components was thus identical with that previously found for Gram-positive bacteria. In the fungi, however, the mycelial walls were composed entirely of carbohydrate. These results suggest that the actinomycetes are not related to the fungi but should be classified with the bacteria proper. On the basis of cell-wall composition a classification of the actinomycetes is proposed, to consist of 3 families: Mycobacteriaceae containing the genera Mycobacterium, Nocardia and Corynebacterium; Streptomycetaceae containing Streptomyces and Micromonospora; and Actinomycetaceae with a single genus Actinomyces. The propionibacteria are probably related to Streptomyces. It is also suggested that a separate order Actinomycetales is unnecessary and that the families proposed can more suitably be included in the Eubacteriales.