How do nitrogen-fixing bacteria help plants grow?

Nitrogen-fixing bacteria support plant growth by converting atmospheric nitrogen—which is largely unusable by most organisms—into inorganic compounds like ammonia that plants can absorb and utilize. This process, known as nitrogen fixation, is essential because nitrogen is a fundamental building block for proteins, DNA, RNA, and chlorophyll.123

These bacteria facilitate plant development through two primary methods:

• Symbiotic Association: Bacteria such as Rhizobium invade the root hairs of host plants, forming root nodules. Within these structures, the bacteria use the enzyme nitrogenase to convert nitrogen into ammonia, which the plant directly consumes for growth.14
• Free-living Contribution: Nonsymbiotic bacteria, such as Azotobacter, fix nitrogen independently in the soil, enriching the environment with nutrients that plants can then uptake.12

By providing this vital nutrient, these microorganisms enable plants to thrive and serve as essential protein sources for other organisms. Farmers often leverage these bacteria through crop rotation and the use of green manures to naturally enhance soil fertility.3