158 



THE ACTINOMYCETES, Vol. I 



large concentrations in the cultures of the 

 sporulating strains of *S'. griseus, but the 

 aerial mycelium-free mutants are capable of 

 forming considerable amounts of this acid. 

 Lactic acid also appears to be a characteristic 

 metabolic product of various nocardias, as 

 shown by von Plotho and others. 



The formation of succinic acid by various 

 species indicates that at least some of the 

 carbohydrate is metabolized through the 

 carboxylic acid cycle. During the growth of 

 S. fradiae in certain poorly buffered media, 

 sufficient acetic acid accumulates to inhibit 

 further growth and metabolism of the or- 

 ganism. In these cases, the accumulated 

 acetate is metabolized when the pH of the 

 medium is raised. Propionic acid has been 

 reported as a metabolite in the growth of 

 micromonospora. 



Cochrane and Dimmick found that, in a 

 glucose medium in the presence of an excess 

 of CaCOs , S. coelicolor produced large 

 amounts of succinic acid, small amounts of 

 lactic acid, and traces of fumaric and an un- 

 identified keto acid. Volatile acids were not 

 detected. This property of forming acids 

 from sugar was believed to be characteristic 

 of the particular species. 



Numerous other investigators reported 

 that actinomycetes are able to produce or- 

 ganic acids from carbohydrates. Magnus 

 observed that many of the actinomycetes 

 found in the larynx are able to form lactic 

 type acids even in sugar-free media, von 

 Plotho confirmed these observations. Wood- 

 ruff and Foster demonstrated that *S'. laven- 

 dulae is capable of producing considerable 

 amounts of lactic acid from carbohydrates. 

 The natun^ of the nitrogen source and the 

 concentration of sugar are of considerable 

 importance in this connection. In the pres- 

 ence of glycnne, more sugar was consumed 

 and less lactic acid produced than with tryp- 

 tone as a source of nitrogen. Without glu(;ose 

 or with low concentrations in the tryptone 

 medium, ammonia accumulated. With 1 per 



cent glucose, the pH was lowered appreci- 

 ably, even in buffered media, as a result of 

 the formation of organic acids; with 2 per 

 cent glucose, especially in unbuffered media, 

 the pH levels went down to as low as 3.2 in 

 2 days. 



Actinomycetes are capable of utilizing 

 readily various organic acids. Some of the 

 higher molecular acids are converted in the 

 process to lower molecular acids. Martin and 

 Batt have shown that the oxidation of pro- 

 pionic acid by cell suspensions of Nocardia 

 corallina is stimulated by carbon dioxide. 

 Thiamine-deficient cells convert propionate 

 to pyruvate with a simultaneous accumula- 

 tion of succinic acid. Two oxidation path- 

 ways to pyruvate were demonstrated; only 

 one of these included a symmetrical inter- 

 mediate (probably succinate). 



According to Masuo and Kondo, various 

 streptomyces accumulate a-ketoglutaric 

 acid, with or without some pyruvic acid 

 from glucose or glycerol. Some organisms 

 convert glycerol to dihydroxyacetone, and 

 D-sorbitol to L-sorbose. 



Among the other metabolic products of 

 actinomycetes, it is sufficient to mention the 

 lactone of (S-hydroxy-Q:,a ,7-trimethyl pi- 

 melic acid, a substance found as a degrada- 

 tion product of certain antibiotics (Anliker 

 et al.). 



Chemical Composition of Actinomy- 

 cetes 



Most of the studies of the chemical com- 

 position of the spores and mycelium of cul- 

 tures of actinomycetes grown on different 

 media have been limited to the elementary 

 composition of the dry cell material. In a 

 few cases, the organic chemical constituents 

 have been examined. The composition of the 

 medium in which the cultures are grown is 

 of considerable importance in this connec- 

 tion. 



Stokes and (lunness concluded that the 

 amino acid content of an organism is, (juali- 



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