Role of Soil Microbes and Their Cell Components in Carbon Stabilization

Fixation of carbon dioxide (CO2) for the production of organic compounds is carried out globally by microbes. These microbes provide food for the survival of heterotrophs in terms of organic C through CO2 fixation. The most familiar pathway of carbon (C) fixation is Calvin–Benson–Bassham cycle. This pathway is adopted by plants, microbes, and algae for inorganic C fixation in natural environment. However, there are a number of other pathways as well that are specifically adopted by microbes for C fixation. By adopting these pathways, microbes follow diversified chemical and biochemical strategies. This chapter is providing basic knowledge about the fixation of CO2 by microbes, mechanism involved in the fixation of CO2, and the enzymes which regulate these mechanisms. Five major pathways, i.e., Calvin-Benson-Bassham cycle, reductive tricarboxylic acid cycle, 3-hydroxypropionic acid (3-HP) cycle, reductive acetyl-CoA (rACo) pathway, and carboxylases, are discussed in this chapter. Four C-fixing pathway enzymes have been described in the chapter. In the near future, it is expected that new pathways will also be established due to number and diversity of microorganisms.