There are three elements in the process of biosynthesis: 1, energy (ATP); 2. Reduce the power ([h]); 3. Raw materials (small molecule precursors)

The important raw material used by autotrophic microorganisms is CO2.

So how to gain energy and reduce energy?

Photoautotrophic microorganisms obtain energy and reducing power through plant photosynthesis or bacterial photosynthesis.

Chemotactic autotrophic bacteria gain energy and reducing power by oxidizing inorganic substances.

The specific process is more complicated.

Take photosynthesis of algae as an example.

The process of utilizing CO2 is CO2 fixation. CO2 fixation includes calvin cycle and reductive tricarboxylic acid cycle. The process of CO2 fixation by algae, sulfur bacteria, iron bacteria and nitrifying bacteria is calvin cycle. Calvin cycle belongs to the dark reaction process of photosynthesis. This process is very complicated (see Baidu's "calvin cycle" for details), and the final result is that CO2 is converted into glucose. This process of fixing CO2 requires energy (ATP) and reducing power ([H]). The way to get these two things is the light reaction of photosynthesis. The process is also quite complicated. Simply put, H2O is photolyzed to generate [H], and ATP is generated by electron transfer.