What is the primary function of nitrogen-fixing bacteria?

The primary function of nitrogen-fixing bacteria is to fix atmospheric nitrogen into chemical compounds. This process is crucial in the nitrogen cycle, as atmospheric nitrogen (N2) is not directly usable by most living organisms. Nitrogen-fixing bacteria convert N2 into ammonia (NH3) and other nitrogenous compounds that can be absorbed by plants, thereby making nitrogen available for incorporation into essential biomolecules like amino acids and nucleic acids.

This process is particularly vital for agriculture, as many crops depend on nitrogen in a form they can utilize, which is provided predominantly by nitrogen-fixing bacteria found in soil or in symbiotic relationships with plant roots, such as those in legumes. This natural fertilization process helps maintain soil fertility and supports the growth of various plants, which are essential for food production and a healthy ecosystem.

Other functions mentioned in the choices, such as decomposing organic matter or producing oxygen, are indeed important processes in ecosystems but are not the primary function of nitrogen-fixing bacteria. These organisms play a specific and critical role in converting nitrogen from the atmosphere into forms that support life on Earth.