On the present earth, nitrogen gas (i.e., N2) is the predominant form of the element. Most organisms cannot utilize this form of nitrogen. Fortunately, some organisms, including anaerobic heterotrophic, anaerobic autotrophic, aerobic bacteria, and cyanobacteria, can “fix” nitrogen (Postgate, 1974). They can convert nitrogen gas to ammonia. Ammonia is then utilized directly by these organisms. Certain plants, the legumes, which are themselves incapable of fixing nitrogen, have a kind of bacterium, rhizobium, attached to their roots. This symbiotic bacterium produces ammonia from nitrogen, and the host plant utilizes it. Ammonia is oxidized by various bacteria including Nitrobacter,to nitrate, which is utilized by other organisms; these latter organisms have mechanisms to reduce nitrate to nitrite and then to ammonia.
KeywordsPhosphorylase Kinase Clostridium Pasteurianum Glucose Tolerance Factor Basic Fitness Corrin Ring
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