78 BACTERIAL FERMENTATIONS 



is decreased; with hypoxanthine the reverse is true. With 

 all three substrates, the purine nitrogen is converted essen- 

 tially quantitatively to ammonia, without any detectable 

 accumulation of urea. The same products are formed by 

 CI. cylindrosporum, except that the yield of formate is 

 higher, approximately 1 mole per mole of purine, and a 

 considerable amount of glycine accumulates. 53 



An early attempt to get some evidence concerning the 

 path of uric acid fermentation was made by investigating 

 the utilization of various compounds previously implicated 

 in the biological oxidation of uric acid. 52 In particular, 

 allantoin and urea, products of uric acid oxidation by both 

 animals and aerobic bacteria, were found not to be attacked 

 by cell suspensions of CI. acidi-urici which rapidly fer- 

 mented uric acid. This appeared to exclude the only known 

 pathway of uric acid decomposition via allantoin and indi- 

 cated that the aerobic and anaerobic pathways must be 

 fundamentally different. 



An indication of the actual mechanism of the purine 

 fermentation was provided by the discovery that glycine is 

 not only formed by CI. cylindrosporum but is also decom- 

 posed by both species under appropriate conditions. The 

 activation of glycine was first shown by the methylene 

 blue reduction technique. Of a considerable number of 

 purines and amino acids tested as reducing agents, using 

 cell suspensions, glycine was by far the most active. When 

 cell suspensions were allowed to act upon glycine alone 

 under anaerobic conditions, essentially no decomposition 

 of the amino acid could be observed. However, when 

 glycine and uric acid were supplied simultaneously, both 

 compounds were decomposed and the amount of glycine 

 consumed was dependent upon the amount of uric acid 

 fermented. This relation, combined with the demonstra- 

 tion that glycine could act as a reducing agent for methylene 



