Waksman — 94 — Actinomycetes 



Production of Pigments:— Actinomycetes are characterized by the 

 production of a variety of pigments both on organic and on synthetic 

 media. Nearly half of all the species isolated and described produce 

 a pigment of one form or another, on one medium or another. These 

 pigments are usually described in terms of various shades of blue, vio- 

 let, red, rose, yellow, green, brown, black. There are also many grada- 

 tions of these colors. The nature and the intensitv of the pigment are 

 greatly influenced by the composition of the medium and environmen- 

 tal growth factors. The pigment may dissolve into the medium or it 

 may be retained in the mycelium. The pigment is concentrated in 

 the vegetative growth in many cases, and only in the aerial mycelium 

 in others. Certain species produce more than one pigment, as is indi- 

 cated by such names as A. violacenis-niher and A. tricolor. Certain 

 brown shades are often superimposed on the main pigment, especially 

 in organic media. 



Some of the pigments are synthetic; others are formed as a result 

 of transformation of certain constituents in the medium. This is true 

 especially of the brown and black pigments produced in protein-con- 

 taining media, as first shown by Cohn, in 1875, and later studied ex- 

 tensively by Beijerinck and many others. 



Production of pigments by actinomycetes has been utilized as an 

 important cultural characteristic in describing the organisms. Never- 

 theless, the ability to form pigments represents one of the most variable 

 properties among the actinomycetes. This variation depends upon 

 many factors, involving not only the nature of the medium, but also 

 the nature and age of the culture and its previous cultivation. The 

 insoluble types of pigments are more constant than the soluble forms. 

 Acids and alkalies exert a marked effect upon the nature and intensity 

 of the pigment. Some of the pigments are soluble in organic solvents, 

 and others are not. 



The production of water-soluble brown to black pigments on organic 

 media is characteristic of certain actinomycetes, mostlv members of the 

 genus Streptomyces. These organisms have usually been designated 

 as chromogenic forms. The nature and the formation of this pigment 

 were first investigated by Beijerinck (25). The tyrosinase action 

 characteristic of these organisims was believed to explain the mechanism 

 of the production of this pigment. It is insoluble in organic solvents, 

 but soluble in water, in dilute acids, and in alkalies. 



According to Afanasiev (6), potato scab organisms failed to pro- 

 duce the melanin pigment in the medium when only tyrosine was pres- 

 ent; however, when other nitrogenous compounds were also added, the 

 black pigment was formed abundantly. This was believed to be due to 

 an alkaline reaction that is favorable to the production of the pigment. 

 It was not formed from other amino acids. All plant pathogenic cul- 

 tures were found to be chromogenic. Although Millard and Burr 

 (298) reported that nonchromogenic actinomycetes may also cause 



