60 PHYSIOLOGY OF BACTERIA 



been outlined in the preceding pages. The recent 

 investigations of Sturges and his associates indicate, 

 however, that with some species at least, the type of 

 decomposition is different. 



Parsons and Sturges (1927) studied the volatile 

 acids produced by Clostr. putrefaciens from pork, and 

 found that acetic, butyric and valeric acids were pro- 

 duced at the molar ratio of 85 : 6 : 9. In gelatin, the relative 

 amount of acetic acid rose even to 91-92.5% of the 

 total acidity. This dominance of acetic acid contrasts 

 Clostr. putrefaciens to most other Clostridia which show 

 a much higher ratio of acids with longer carbon chains. 



The only exception is Clostr. histolyticum (Sturges, 

 Parsons and Drake, 1929) which produces acetic acid 

 only; non- volatile, ether-soluble acids could not be 

 detected. This holds true for such widely different 

 media as milk, beef heart, brain, liver, gelatin and peptone. 



The large amount of acetic acid formed by Clostr. 

 histolyticum cannot have been derived from deaminiza- 

 tion of glycine, because even in a gelatin medium (con- 

 taining 25 % of glycine) the acetic acid formed is almost 

 twice the theoretical amount from the glycine, and in a 

 pork medium, it is more than ten times the theoretical 

 amount. 



Sturges, Parsons and Drake conclude that this organ- 

 ism, and possibly all putrefactive anaerobes, either 

 have some highly specific method of splitting proteins, 

 differing radically from the usually accepted hydrolysis, 

 or that they can split long-chain amino acids into acetic 

 acid and some still undiscovered residues. 



Urea Fermentation. — The urea fermentation is usually 

 summed up in the formula: 



CO(NH2)2 + 2H2O = C03(NH4)2 



