Organisms that can grow with carbon dioxide as the main carbon source in nature are collectively called autotrophs. It mainly includes 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 is converted into carbohydrates through a series of complicated processes under the condition of energy demand. The energy required for growth varies according to microbial groups and is obtained by photosynthesis or chemical synthesis respectively. The former are purple sulfur bacteria and green sulfur bacteria, while the latter are nitrifying bacteria, sulfur bacteria, iron bacteria and hydrogen bacteria. Autotrophic organisms play an important role in the transformation of natural substances.