Role of Cyanobacteria in Rhizospheric Nitrogen Fixation

An innumerable group of microorganisms are associated with plants and present in the phyllosphere, rhizosphere, and endosphere. They produce different metabolites—such as amino acids, proteins, polysaccharides, and vitamins—that affect plant growth and help to improve soil fertility and crop production naturally. Furthermore, among all inhabitants of the rhizosphere, cyanobacteria are among the foremost organisms, with potential to contribute to biological nitrogen fixation. They contain a specialized type of cell (a heterocyst), which is considered the actual site of dinitrogen fixation in cyanobacteria. Bryophyte–cyanobacterial associations are significant sources of nitrogen fixation in terrestrial ecosystems such as boreal forests. Therefore, cyanobacterial inoculants are influential biofertilizers in sustainable agriculture. This chapter describes beneficial aspects of nitrogen fixation by cyanobacteria in the rhizosphere and the role of cyanobacteria in increasing soil fertility, which leads to improved crop productivity.