Chapter V — 97^ Metabolism 



color could be extracted with cold and hot water as well as with alcohol. 

 This pigment became red when treated with acid, and green when 

 treated with 25 per cent alkali solution. The addition of lead acetate 

 to an aqueous solution of the pigment brought about formation of a 

 violet precipitate. As has been pointed out, this pigment was believed 

 to belong to the anthocyanins, a fact not confirmed (116) by further 

 study. 



Krassilnikov (234) confirmed the observations of Kriss, that an- 

 thocvanins or allied pigments are characteristic of several actinomycetes. 

 The pigment of N. cyanea is soluble in water and in aqueous solutions 

 of alcohol, but not in pure alcohol, acetone, ether, or chloroform. It 

 does not change in color in an acid medium, although in dilute acids 

 the pigment assumes a rose-violet shade; strong acids decolorize the pig- 

 ment. It is produced only on synthetic media with sucrose and glu- 

 cose as carbon sources. 



Green actinomycetes also produce a water-soluble green pigment, 

 which is the reason for such species names as A. viridis, A. virido- 

 chromogeniis, and A. verne. The pigment is also soluble in glycerol 

 and in alkali solutions, but not in organic solvents. 



The water-insoluble pigments have been studied only to a limited 

 extent. Among these, the carotenoids produced by the red, orange, 

 and yellow species are of particular interest (234). Reader (354) 

 demonstrated two such pigments among actinomycetes; one of these 

 pigments was designated as corallin, an ether solution of which gives 

 two bands of absorption in the spectrum. 



The significance of the various pigments, especially the brown and 

 black types, in the nutrition of actinomycetes is still a matter of specula- 

 tion. ScHiBATA (396) suggested that they play a role in the oxygen 

 exchange between the atmosphere and the cells in a manner similar to 

 the role of hemoglobin in animals. Protective mechanisms have been 

 postulated for some of the pigments (234). 



Thermophilic Actinomycetes:— Among the thermophilic microor- 

 ganisms, or those capable of growing at higher temperatures, such as 

 50° to 65 °C, the actinomycetes occupy a prominent place. In view of 

 the fact that these organisms occur so abundantly in organic matter-rich 

 materials, one would naturally expect that they should be abundant 

 in high temperature in heaps of hay, composts, and in soils, as will be 

 shown later (p. 144). They are also found in a number of other 

 substrates, such as pasteurized cheese (36). 



The abundance of thermophilic actinomycetes in nature has been 

 knovm since the work of Globig (138), in 1888. Tsiklinsky (429) 

 was the first to establish, in 1899, that composts contain an abundance 

 of actinomvcetes. The normal temperature for their growth ranges 

 from 50° to 70 °C. 



