Organisms that can grow with carbon dioxide as the main carbon source in nature are collectively called autotrophs, mainly including plants and a few microbial groups.

These microorganisms all use carbon dioxide as the main carbon source and inorganic nitride as the nitrogen source. Carbon dioxide is mainly fixed by calvin cycle (i.e. photosynthetic carbon cycle) and converted into carbohydrates through a series of complicated processes when energy is needed. The energy required for growth varies with microbial groups and is obtained by photosynthesis or chemical synthesis respectively. The former is purple sulfur bacteria and green sulfur bacteria, while the latter is nitrification.