Which symbiotic bacterium is responsible for nitrogen fixation?

Rhizobium

The correct answer is Option (1) - Rhizobium

• Explanation:
• Rhizobium is a symbiotic bacterium that forms nodules on the roots of leguminous plants. This symbiotic relationship is beneficial for both the bacterium and the plant. Rhizobium is known for its ability to fix atmospheric nitrogen into a form that the plant can utilize. This nitrogen-fixing process enhances soil fertility and the plant's nutrient availability. Pseudomonas, Lactobacillus, and Azotobacter are bacteria with different roles, and they are not primarily associated with nitrogen fixation in the context of symbiosis with leguminous plants.