Question

Which of the following is recently discovered Gram positive non - leguminous nitrogen fixing bacterium?

• A. Azospirillum
• B. Rhizobium
• C. Nitrosomonas
• D. Spirillum

Answer 1

The correct option is A Azospirillum

Azospirillum is a free-living non-leguminous nitrogen fixing bacteria which colonize on the root surface. It can convert atmospheric nitrogen into ammonium under microaerobic conditions at low nitrogen levels, through the action of the nitrogenase complex. Rhizobia are the nitrogen-fixing bacteria that form a symbiotic association with roots of leguminous plants.They fix atmospheric nitrogen (N${}_2$) into organic form (NH${}_3$) by an enzyme called nitrogenase. Nitrosomonas are almost always found in consortium with Nitrobacter. Nitrosomonas convert ammonium to nitrite (NO${}_2$${}^{-}$) and Nitrobacter convert nitrite to nitrate (NO${}_3$${}^{-}$). Spirillum is a genus of free-living gram-negative atmospheric nitrogen fixing bacteria.

Thus, the correct answer is option A.