Answer:
Two kinds of nitrogen-fixing microorganisms are recognized: free-living nonsymbiotic bacteria, including the cyanobacteria or blue-green algae Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium; and mutualistic symbiotic bacteria such as Rhizobium, associated with leguminous plants,.
Step-by-step explanation: