Waksman — 86 — Actinomycetes 



tures, the corresponding efficiency under submerged conditions being 

 only 21 to 23 per cent (517). As growth progresses, the carbon effi- 

 ciency drops. After growth of the organism reaches a maximum, less 

 synthesis takes place. If lysis sets in, the mycelium is destroyed and 

 CO2 and NH3 are liberated. 



The ratio of consumption of carbohydrate to utilization of nitrogen 

 depends upon conditions of growth, nature of organism, and age of cul- 

 ture. With sugar and tryptone in the medium, the ratio increases to 

 about 300 per cent as growth advances, thus pointing to greater oxida- 

 tion of the carbohydrate in relation to the utilization of tr)'ptone for cell 

 synthesis. This is true especially for submerged cultures, where the 

 abundance of available oxvgen leads to greater oxidation of carbohydrate 

 as compared to the tryptone consumed. 



Acid froduction hy actinomycetes.— As a result of the growth of ac- 

 tinomycetes in different media, there is always a tendency for the reac- 



Table 13: Acid production by an actinomyces on 

 meat extract-peptone-glucose medium (340) : — 



* Original pW of medium 5 8, 25 days incubation. 



tion to become alkaline unless ammonium salts or organic acids are the 

 sole source of nitrogen, with the result that acid ions accumulate in the 

 medium. In the presence of carbohydrates, however, certain organisms 

 are capable of producing certain organic acids, the concentration of the 

 latter depending on the nature of carbohydrate and its concentration. 

 Sooner or later, however, the acid will be decomposed or the organisms 

 will produce neutralizing substances, with the result that the reaction 

 always tends to become alkaline. The tendency is toward the attain- 

 ment of a maximum alkalinity, which is usually 8.6 to 8.8. 



The alkaline reaction thus produced by actinomycetes is largely due 

 to certain secondary reactions in the medium, such as the accumulation 

 of the basic ion (Na, K) when nitrates are used in the medium as 

 sources of nitrogen, or to the formation of ammonium ions from pro- 

 teins. The fact that certain actinomycetes do not occur in soils having 

 a pH lower than 5.2 was at one time considered to substantiate the asso- 

 ciation of actinomycetes with alkaline reactions. It has now been estab- 

 lished, however, that even fairly acid soils contain a considerable num- 



