Microbes are the general name of all tiny organisms that are invisible or unclear to the naked eye. It is a large class of organisms, including bacteria, viruses, fungi, some small protozoa, microalgae and so on. Although it is small, it is closely related to human life.

According to the different carbon and energy sources of microorganisms, there are four life types. ：

Chemotactic autotroph: An organism, such as nitrifying bacteria, uses inorganic CO2 as a carbon source to oxidize inorganic substances to generate energy, thus synthesizing its own organic matter.

Photoenergy heterotrophy: this kind is rare, which refers to organisms that use organic matter as C source and light energy as energy to synthesize organic matter.

Chemotaxis-heterotrophy: This is the nutrition mode of most animals and bacteria, which uses organic matter as C source and energy to synthesize its own organic matter.

Microorganisms are autotrophic.