Waksman — 80 — Actinomycetes 



In contrast to this simple mode of nutrition, the other extreme may 

 be found in a manure pile. When stable manure consisting of animal 

 excreta mixed with bedding is allowed to lie in an open pile, with air 

 freely admitted, rapid decomposition sets in, as can easily be detected by 

 extensive solution of COo and NH3 and by a rise in temperature. 

 When the temperature reaches 60° to 65 °C., numerous white patches 

 can be seen throughout the pile. When slides are buried in such a pile, 

 then removed and stained, actinomyces growth is found in great abun- 

 dance. Attempts to cultivate these organisms meet with great difficultv, 

 however, largely because the artificial conditions of nutrition do not 

 quite approach the natural nutrients and environment. 



The actinomycetes as a group obtain their nutrition between the two 

 extremes illustrated. It is no wonder, then, that a great variety of media 

 have been introduced for the growth of actinomycetes. These media 

 are synthetic and organic in nature. For the purpose of cultivation, 

 especially for determining the morphological and cultural properties of 

 the organisms, synthetic media are commonly used. A number of such 

 media are described in the appendix. For certain purposes, however, 

 organic media are required. This is true particularly in the growth of 

 S. griseits for production of streptomycin. In this case, a complex or- 

 ganic substance in the nature of meat extract, yeast extract, corn steep, 

 soybean meal, and others is found necessary for the rapid production of 

 the antibiotic. Although streptomycin and streptothricin can be pro- 

 duced in simple synthetic media, the process is much slower and lower 

 yields are obtained. 



Carhon sortrces.— Under natural conditions, actinomycetes live on 

 a large number of substrates. They are able to utilize a great variety of 

 simple and complex organic compounds as sources of carbon and of en- 

 ergy. These compounds include organic acids, sugars, starches, hemi- 

 celluloses and cellulose, proteins, polvpeptides and amino acids, nitrogen 

 bases, and many others. Certain actinomycetes can also attack, to a 

 more limited extent, fats, hydrocarbons, benzene ring compounds, and 

 even such resistant substances as lignin, tannin, and rubber. There 

 is considerable selectivity in the utilization of these materials, some sub- 

 tances being consumed far more readily than others. Glucose, maltose, 

 dextrin, starch, glycerol, organic acids, and proteins are the best sources 

 of carbon; these are followed by sucrose and other sugars, by sugar al- 

 cohols, and by sugar acids (309). Cellulose is attacked only by certain 

 organisms. Agar also can be used as a source of carbon and energy by 

 some actinomycetes, notably certain strains of S. coelicolor (363). 



As a rule, actinomycetes prefer proteins to carbohydrates as sources 

 of carbon. This preference is so pronounced that when a protein or a 

 protein derivative, such as peptone, and glucose or another available 

 carbohydrate are present in the same medium, an actinomyces attacks 

 the protein first, not only as a source of nitrogen but also as a source of 



