ENERGY TRANSFORMATION 



395 



presence of ferric hydroxide to a considerable extent. The important 

 role of iron was also established for the growth and respiration of 

 various other bacteria. 



As to the energy utilization of the bacteria oxidizing ammonium 

 salts, the following results of Winogradsky are illuminating: 



N oxidized (from NHj to NOj), 



mgm 722.0 506.1 928.3 815.4 



C assimilated (from CO.), mgm 19.7 15.2 26.4 22.4 



N:Cratio 36.8 33.3 35.2 36.4 



About 35 parts of nitrogen were thus found to be changed from am- 

 monia to nitrite for every part of carbon assimilated from the CO2 of 



TABLE 25 

 Influence of organic matter upon the growth of nitrite and nitrate-forming bacteria 



the atmosphere. Similar results were obtained by Meyerhof. In 

 the process of oxidation of ammonia to nitrite four times as much 

 energy (78.4 Calories per mol) is liberated as in the process of oxida- 

 tion of nitrite to nitrate (18.8 Calories per mol). But four times as 

 much nitrogen is transformed in the latter processes (N:C = 135). 

 The utilization of energy for chemosynthesis of carbon is, therefore, 

 almost identical and is equivalent to about 5 per cent. 



With an active culture under proper conditions, the process of oxi- 

 dation of ammonium salts is very rapid. Meyerhof found that, with 

 a maximum aeration, 4 grams of ammonium sulfate are oxidized to 

 nitrite in one liter of medium in 24 hours. Respiration decreases with 

 a decrease in oxygen concentration, the reaction being reversible. 

 The reaction optimum for respiration is at a pH 8.4 to 8.8, with mini- 



