Question

Which among the following are the Free-living nitrogen fixing bacteria?

Which of the above statement(s) is/are correct?

• A. Only 1, 3 & 4
• B. Only 1, 2 & 3
• C. Only 2, 3 & 4
• D. All of the above

Answer 1

The correct option is C Only 2, 3 & 4

Two kinds of nitrogen-fixing bacteria are recognized:

1. Free-living (non-symbiotic) bacteria, including the cyanobacteria (or blue-green algae) Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium;
2. Mutualistic (symbiotic) bacteria such as Rhizobium, associated with leguminous plants (e.g., various members of the pea family), and certain Azospirillum species, associated with cereal grasses.