Rhizobia is a heterotrophic aerobic type, which can only fix nitrogen when it coexists with some green plants, but can't fix nitrogen when it lives alone.

Don't live in an environment lacking nitrogen.

Chromospheric azotobacter is an autotrophic azotobacter, which belongs to heterotrophic aerobic type and can survive in nitrogen-deficient medium (it is independent of other organisms and can fix nitrogen independently in soil or medium).

Relationship between them: both of them can convert air into NH3, and they are prokaryotes (the nitrogen-containing gene is located on plasmid DNA molecule, and the coding region of the gene is continuous).