Root nodules of leguminous plants contain which nitrogen-fixing bacteria?
Answer and explanation
Correct answer: B. Rhizobium
- Step 1: Biological nitrogen fixation reduces atmospheric gaseous nitrogen () to ammonia (), catalyzed by the oxygen-sensitive enzyme nitrogenase.
- Step 2: Symbiotic nitrogen fixation in leguminous root nodules is carried out by bacteria of the genus Rhizobium, which differentiate into nitrogen-fixing bacteroids within nodule tissues supported by leghemoglobin.
Answer
Rhizobium.
Why not the others: 'Nitrosomonas' is a free-living chemoautotrophic nitrifying bacterium that oxidizes ammonia to nitrite; 'Azolla' is an aquatic fern that forms a symbiotic relationship with cyanobacterium Anabaena azollae; 'Escherichia' (E. coli) is a non-nitrogen-fixing enteric bacterium.
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