What is the importance of nitrogen-fixing bacteria in the nitrogen cycle?

Nitrogen-fixing bacteria play a crucial role in the nitrogen cycle by converting atmospheric nitrogen (N₂) into a form that is usable by plants, primarily ammonia (NH₃). Most plants cannot utilize atmospheric nitrogen directly due to its stable diatomic form. Instead, they depend on these specialized bacteria, which possess the enzymatic capability to break the triple bond of nitrogen gas and transform it into inorganic compounds that plants can absorb through their roots.

This process is vital for the growth and health of terrestrial ecosystems since nitrogen is an essential nutrient that supports the synthesis of amino acids, proteins, and nucleic acids in plants. By facilitating the conversion of inert atmospheric nitrogen into bioavailable forms, nitrogen-fixing bacteria not only enhance soil fertility but also contribute significantly to the productivity of agricultural systems.

The other options present functions that, while related to the broader ecological processes, do not accurately capture the specific and fundamental role nitrogen-fixing bacteria play in making nitrogen accessible to plants.