Question
The free-living, anaerobic nitrogen - fixer is
-
Beijerinckia
-
Rhodospirillum
-
Rhizobium
-
Azotobacter
Solution
B.
Rhodospirillum
Rhodospirillum is free - living, anaerobic, nitrogen fixer. Both Beijerinckia and Azotobacter are free-living, nitrogen - fixing, aerobic microbes. Rhizobium is a symbiotic, nitrogen-fixer.