Question

One of the free-living anaerobic nitrogen fixer is:

• A. Azotobacter
• B. Beijerinckia
• C. Rhodospirillum
• D. Rhizobium

Answer 1

The correct option is C

Rhodospirillum

Nitrogen fixers can be of two types - free-living and symbiotic. Free-living or non-symbiotic nitrogen fixers are the microorganisms that live freely or outside the plant cell. For example free-living non-photosynthetic aerobic nitrogen fixing bacteria are Azotobacter, Beijerinckia and Derxia. Free-living non-photosynthetic anaerobic nitrogen fixing bacteria include Clostridium. Symbiotic nitrogen fixers are microbes which are mutually associated with plants and fix atmospheric nitrogen within plant cell. Example of a nitrogen fixer is Rhizobium that fixes nitrogen in roots of leguminous plants.