SOME ASPECTS OF NITRATE REDUCTION 



Independently this problem had also been attacked in my labora- 

 tory by Mr. J. J. C. Goos. Since in these experiments a different bacte- 

 rial species, viz., Pseudomonas aeruginosa, and also a different hydrogen 

 donator, viz., glucose, have been used, it seems worth while to report 

 the results obtained, the more so because also oxido-reduction balances 

 have been drawn up. 



As for the carbon balances the results have been collected in 

 Table II: 



TABLE II 



Carbon balance in nitrate reduction by Pseudomonas aeruginosa with 

 glucose as hydrogen donator 



It should be remarked that the amount of carbon present in the 

 bacteria has been estimated by an indirect method. At the end of the 

 experiments the amount of protein present has been determined by the 

 Kjeldahl-method. Since both the protein content and the carbon 

 content of the dry bacteria may be assumed to be about 50 %, this 

 means that in first approximation the two values are interchangeable. 

 The errors introduced by this procedure can only be of minor im- 

 portance, and the figures leave no doubt that the carbon of the glucose 

 consumed, in as far as not recovered in the bacteria, is almost quan- 

 titatively found back as carbon dioxide. 



The oxido-reduction balances support this conclusion. 



It seemed, nevertheless, dangerous to generalize this conclusion, 

 because we know of several instances in which of two related bacterial 



493 



