1, autotrophic nitrogen-fixing bacteria, refers to a kind of microorganisms that can fix nitrogen independently without relying on other organisms. Autotrophic (a variety of cyanobacteria, such as Nostoc commune, Anabaena commune, etc. ), heterotrophic.

2.* * * azotobacters refers to a kind of microorganisms, which can only fix nitrogen when they coexist with other organisms.

3. Combined nitrogen-fixing bacteria refer to a kind of microorganisms that must live in the rhizosphere of plants, foliage or intestinal tract of animals to fix nitrogen.

In short, nitrogen-fixing microorganisms are autotrophic and heterotrophic.