508 



PRINCIPLES OF SOIL MICROBIOLOGY 



A small amount of sugar (0.05 per cent) may even have a stimu- 

 lating effect on the formation of ammonia from casein by causing an 

 increase in the numbers of bacteria. After the sugar has all been 

 decomposed, the increased numbers of bacteria will bring about a 

 greater consumption of energy and, therefore, a greater decomposition 

 of the protein and liberation of ammonia. A change from a depressing 

 to a stimulating effect by the addition of a small amount of available 

 carbohydrate upon the accumulation of ammonia from dried blood is 



TABLE 46 



Influence of various concentrations of glucose on the formation of ammonia 



from casein 2 



C = casein, G = glucose; Bact. = bacteria in millions. 



illustrated in fig. 30. In the presence of undecomposed organic matter, 

 the soluble nitrogen salts are transformed into insoluble proteins; these 

 compounds will be decomposed later and make the nitrogen compounds 

 available again. 5 



Since the formation of ammonia is a prerequisite to nitrate formation, 

 one would expect from these results that an excess of available energy 



8 Gerlach and Deusch. Uber den Einflusz organischer Substanzen auf die 

 Umsetzung und Wirkung stickstoffhaltiger Verbindungen. Mitt. Kais. Wilh. 

 Inst. Landw. Bromberg, 4: 259. 1912; (Centrbl. Bakt. II, 37: 296. 1913). 



