FERMENTATIONS OF NITROGENOUS COMPOUNDS 87 



pends upon the relative activities of the enzyme systems. 

 With CI. cylindrosporum, glycine and formate accumulate 

 in substantial amounts and therefore the enzyme system 

 leading to ATP is probably more active. With CI. acidi- 

 urici, on the contrary, nearly all of the glycine moiety of 

 formiminoglycine is converted to acetate and carbon diox- 

 ide, indicating a very active formyl transferring system. 



The studies summarized above have established the 

 general pathway of the clostridial purine fermentation, al- 

 though obviously several aspects of the process, particularly 

 the incorporation of carbon dioxide into acetate and gly- 

 cine 71 and the assumed formation of serine, need to be 

 investigated more fully. 



The ability to ferment purines is not restricted to Clos- 

 tridia. Two anaerobic micrococci, M. aerogenes™ and 

 M. lactilyticus, 72 are able to grow in a complex medium at 

 the expense of certain purines and carry out a modified 

 propionic acid-type fermentation. These purine fermenta- 

 tions have not been studied extensively but the experiments 

 of Whiteley show that M. aerogenes forms considerable 

 amounts of uracil and thymine during the decomposition of 

 xanthine. This indicates that the initial enzymatic attack 

 may be on the imidazole ring in contrast to what has been 

 found with the purine fermenting Clostridia. 



These studies of the fermentations of nitrogen com- 

 pounds have led to the discovery of several metabolic path- 

 ways not previously encountered in other organisms. There 

 is no reason to believe that these pathways are restricted to 

 anaerobic bacteria. Indeed the whole history of biochem- 

 istry indicates that any reaction discovered in one organism 

 is ultimately found to occur in many others. Anaerobic 

 bacteria obviously provide excellent and often neglected 

 biological material for the study of certain types of meta- 



