(1), as an ecological term, is also called an independent vegetative organism, and the corresponding word is heterotrophs. Its original meaning refers to organisms that live and reproduce only with inorganic compounds as nutrients. In this classical concept, there is no difference between the two metabolic systems, that is, substrate oxidation for energy and nutrient reduction for carbon assimilation. Today, this concept has been classified according to the nutrients oxidized into energy and their oxidation forms (chemosynthetic organisms, photosynthetic organisms, inorganic oxidizing organisms and organic oxidizing organisms), according to the intake mode of carbon source nutrients and the synthesis mode of organic metabolites necessary for reduction and assimilation. And it is widely used only in the latter sense.

(2) Organisms that survive and reproduce by inorganic nutrition are the corresponding words of organic nutritious organisms. Organisms that assimilate carbon by using energy obtained from chemical dark reactions such as respiration or photochemical reactions are called chemoautotrophs and photoautotrophs respectively. Representative examples of autotrophic microorganisms are red sulfur-free bacteria, red sulfur bacteria, green sulfur bacteria, nitrifying bacteria, sulfur bacteria, hydrogen bacteria, iron bacteria, carbon monoxide bacteria and so on. 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.