These organisms are relatively primitive bacterial prokaryotes, such as nitrifying bacteria, sulfur bacteria, iron bacteria and so on.
Nitrifying bacteria are compounds that can oxidize inorganic nitrogen and gain energy from it, thus synthesizing CO2 into organic matter.
Sulfur bacteria can oxidize H2S and accumulate sulfur in the body. If H2S is lacking in the environment, the bacteria will oxidize sulfur in the body into sulfuric acid. Sulfur bacteria use the energy released by the above two reactions to synthesize organic matter.
Iron bacteria is a kind of bacteria that can oxidize ferrous sulfate, and the energy released in this process is used to synthesize organic matter.
There are not many kinds of autotrophic bacteria in nature, and the specificity of oxidized inorganic substances is very strong. For example, sulfate bacteria can only oxidize sulfur and hydrogen sulfide, nitrite bacteria can only oxidize ammonium salt, nitrate bacteria can only oxidize nitrite, and iron bacteria can only oxidize ferrous salt.