Representative examples of autotrophic microorganisms are red sulfur-free bacteria, red sulfur bacteria, green sulfur bacteria, nitrifying bacteria, sulfur bacteria, hydrogen bacteria, iron bacteria and carbon monoxide bacteria (except denitrifying bacteria). In autotrophic microorganisms, such as hydrogen bacteria, with the substitution of available electron donors (for example, acetic acid is produced from hydrogen), it can sometimes be seen that carbonic acid assimilation replaces the reductive assimilation of organic nutrients (acetic acid, etc.). ). The same mechanism of carbon fixation cycle and energy harvesting system, as well as the regulation mechanism of autotrophs on the adaptive function of organic matter are being compared with photosynthetic organisms in order to clarify biochemically.