HOW DO MICROBES "FIX" NITROGEN FROM THE AIR? — NICHOLAS 451 



REDUCTION '.energy required 



Dcnitriffcation. Rxatlon 



Nitrate ^ Nitrogen |^ Ammonia' 



gas 



Protein 



synthesis 



(Micro-organisms 



and green 



plants) 



-Nitrite 

 Nitrification 



OXIDATION: energy required 



Animals 



Figure 2.— Principal reactions in the nitrogen cycle in nature. 



Table 1. — Asymiiotic and syniMotic microorganisms which fix nitrogen gas 



^66-74&— 65- 



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