Which of the following options is responsible for converting atmospheric nitrogen into a form that can be used by plants and animals?

Although the atmosphere contains about 70% nitrogen, plants cannot utilise this form of the element. Nitrogen fixation is the process of converting atmospheric nitrogen into a form that can be utilised by plants and animals. This process is carried out by nitrogen-fixing bacteria and other microbes, which have the ability to convert nitrogen gas into ammonia (NH₃) through a process called nitrogen fixation. This ammonia can then be used by plants and animals to build proteins and other essential molecules.

In leguminous plants, nitrogen-fixing bacteria form symbiotic relationships with the plant roots, where they live in root nodules and fix nitrogen for the plant to use. Other types of nitrogen-fixing bacteria are free-living in the soil or water, and some are even found in association with other types of plants or animals. Some examples of nitrogen-fixing bacteria include Rhizobium, Azotobacter, and Cyanobacteria.