What is the role of nitrogen-fixing bacteria?

Nitrogen-fixing bacteria play a crucial role in the nitrogen cycle by converting atmospheric nitrogen (N2), which most plants cannot use, into forms that are available for plant uptake, such as ammonia (NH3). This process, known as nitrogen fixation, is vital because nitrogen is an essential nutrient for plant growth, being a key component of amino acids, proteins, and nucleic acids.

The ability of these bacteria to transform nitrogen gas into a usable form not only supports plant health and growth but also contributes to soil fertility. Many plants form symbiotic relationships with nitrogen-fixing bacteria, such as those in the genus Rhizobium, which live in root nodules of legumes. In return for sugars and other organic compounds from the plant, these bacteria provide the plants with an important nutrient source, which enhances agricultural productivity and ecosystem health.

This symbiotic relationship is essential in maintaining the balance of nutrients in an ecosystem, ultimately supporting herbivores and higher trophic levels that depend on healthy plant communities. The other options do not accurately reflect the primary role of nitrogen-fixing bacteria in the ecosystem.