Aerobic Bacteria 



197 



Linc\vca\cr obscr\ccl tliis cfFcct in conci'utrations ot 0.5 iiig NO3-N 

 or NH4-N per 100 ml of nietliuin. 



Azotohactcr transforms the carbon componnds into carl)on dioxide, 

 water, and cell substance. The amount of mtro<ji;en fixed is about 10 



Fig. 83. Clostridium pasteiiiiamim (from Winogradsky ) . 



mg per gram of sugar consumed. Other carbon compounds are util- 

 ized in proportion to their availability, as shown in Table 41. The 



Table 41. Nitrogen Fixed by Azotohader chroococcian with Different Sources 



OF Energy 



Milligrams of nitrogen fixed per 100 gm of carbon available. 



efficiency of nitrogen fixation also depends upon the type of organ- 

 ism, experimental conditions, and presence of contaminants, as 

 shown in Tables 42 and 43. 



Azotobacter is widely distributed in the soil, although only a rela- 

 tively limited number of cells are found in any one soil. The reac- 

 tion of the soil, the abundance of organic matter, the concentration 

 of certain mineral elements, notably phosphate, and the absence of 



