Waksman — 82 — Actinomycetes 



Among the organic acids, formic, oxalic, tartaric, and hippuric are 

 unfavorable carbon sources; acetic, citric, and malic are favorable (307). 

 Ethyl alcohol and ethylene glycol (also erythritol and dulcitol) are un- 

 favorable sources; on the other hand, glycerol and mannitol are highly 

 favorable. Starch is an excellent source of carbon for a large number 

 of actinomycetes. Various hemicelluloses, such as mannans, are readily 

 utilized. 



The ability of actinomycetes to utilize carbon sources has often been 

 used as an aid in species differentiation, especially among species of 

 Streptomyces. Pridham and Gottlieb (348) reported that all species 

 are able to utilize ci-glucose, if-mannose, starch, dextrin and glvcerol, but 

 not erythritol, phenol, cresol and the sodium salts of formic, oxalic and 

 tartaric acids. Certain compounds, however, may be utilized by certain 

 species and not by others. This is true of rhamnose, raffinose, xylose, 

 lactose, mannose, dulcitol, inositol and the sodium salts of acetic and 

 succinic acids. 



Since the wide interest in the production of antibiotics by actinomy- 

 cetes has arisen, numerous investigations have been carried out on their 

 ability to utilize carbon sources from the point of view of the production 

 of a particular antibiotic. In the case of streptomycin, for example, 

 pentoses were poor carbon sources; among the hexoses, glucose and man- 

 nose were best, the latter being particularly effective when combined 

 with 1 (— ) proline, maltose was the best of the disaccharides; the trisac- 

 charides were inferior; of the polysaccharides, inulin was inferior to 

 starch and dextrin, among the alcohols, mannitol was a promising car- 

 bon source; none of the organic acids proved to be suitable (100). 



Nitrogen sowrces.— Actinomycetes are unable to fix atmospheric ni- 

 trogen. Proteins, peptones, and amino acids form the best sources of 

 this nutrient for actinomycetes. These are followed by nitrates and 

 ammonium salts. The former is sometimes considered (309) better than 

 the latter, possibly because of the residual effect of the basic ion left 

 from the nitrate as compared with the acid ion left from the ammonium 

 salt, which makes the medium less favorable for the growth of actinomy- 

 cetes. Ammonium sulfate is utilized better than ammonium chloride. 

 Urea and uric acid are readily utilized and converted into complex 

 organic compounds. Some forms of actinomycetes are able also to use 

 nitrites in low concentrations as sources of nitrogen. 



The capacity for decomposing proteins is widely distributed among 

 actinomycetes. This is shown by the fact that the great majority of 

 actinomycetes are able to liquefy gelatin; the only nonliquefying forms 

 so far known are among the nocardias, notably N. asteroides. Actino- 

 mycetes are able to coagulate milk, and later peptonize it; in fact, pep- 

 tonization commonly occurs without previous coagulation. Coagulation 

 of the milk is a proteolytic effect, due to formation of specific enzymes, 

 rather than an acid effect. Blood serum is liquefied by many of the 

 species. Complex proteins, such as hoof meal and horn meal, are also 



