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 media, it came to be 

 recognized that different organisms are able 

 to produce a great variety of pigments, rang- 

 ing from red to blue and from orange and 

 yellow to brown and black. Some are single 

 pigments, and others comprise two or more 

 constituent pigments. Some are water-sol- 

 uble and others are water-insoluble, as shown 

 in detail in Chapter 13 of Volume I. The 

 presence of oxygen is essential for pigment 

 formation. The pH of the medium greatly 

 affects the nature of the pigments, both in- 

 soluble and soluble. 



When cultures are grown on optimum 

 sporulation media, the pigmentation of the 

 spores is highly significant; it may be ob- 

 served at an early growth stage, at maturity, 

 or only in old cultures, since changes in color 

 may occur with age of culture. 



Tin 1 formation of deep brown to black pig- 

 ment- on organic media containing proteins 



