Biological dinitrogen (N2) fixation: introduction and nonsymbiotic

In this chapter you will be introduced to some of the fundamentals of the process of biological N2 fixation and the nature of the enzyme complex, nitrogenase, which mediates the conversion of N2 to NH3. The process is unique in that, so far as is known, only prokaryotic microbes possess this enzyme system. Despite the cumbersome nature of the nitrogenase enzyme complex, about one half–two thirds of the global supply of fixed N comes through biological N2 fixation. Nitrogen fixation occurs in a wide range of habitats wherever sufficient energy supplies and appropriate environmental conditions exist.