. The actinomycetes. Actinomycetales. 70 THE ACTINOMYCETES, Vol. II. Figure 20. Sclerotium in species of Slrepto- myces, designated as new genus Chainia (Prepared by H. Lechevalier, Institute of Microbiology). According to Krassilnikov (1955, 1959, 1960), the nature of the sporophore is a per- manent property, being straight in the S. globisporus group, spiral-shaped in the S. coelicolor and S. violaceus groups. The same constancy is true of the shape of the spores, cylindrical versus oval or spherical, and of the manner of spore formation, namely, frag- mentation versus segmentation. Branchin
. The actinomycetes. Actinomycetales. 70 THE ACTINOMYCETES, Vol. II. Figure 20. Sclerotium in species of Slrepto- myces, designated as new genus Chainia (Prepared by H. Lechevalier, Institute of Microbiology). According to Krassilnikov (1955, 1959, 1960), the nature of the sporophore is a per- manent property, being straight in the S. globisporus group, spiral-shaped in the S. coelicolor and S. violaceus groups. The same constancy is true of the shape of the spores, cylindrical versus oval or spherical, and of the manner of spore formation, namely, frag- mentation versus segmentation. Branching of the sporophores, namely, vertical forma- tion versus monopodia] branching, is also a constant, although a variable, property. No single property, however, is sufficient to characterize species. Coremia formation (Fig. 17) is of no taxonomic significance; however, production of sclerotia is believed to be a constant property, in agreement with Thirumalachar (1955), bu1 not with Gattani (1957), who denied its significance (Figs. 18-20). Cultural and Biochemical Characteristics FORMATION OF PIGMENTS Among the cultural properties of strepto- mycetes, the color of the substrate growth of the aerial mycelium and the spores and the formation of soluble pigments in organic and synthetic media play a major role in characterizing species. This fact is amply illustrated by the numerous specific epithets referring to color that have been used to designate various organisms. Unfortunately, color characteristics vary greatly with age of the culture, composition of the medium, temperature of incubation, and nature of the inoculum. Before the introduction of synthetic me- dia, it was a common practice to divide the actinomycetes into two groups: (a) colorless or nonchromogenic, and (b) pigment-produc- ing or chromogenic forms. The latter com- prised those organisms that produced deep brown to black diffusible pigments when grown on proteinaceous media. With the in- troduction of synthetic
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