Here's how it works:

* Nitrogen gas (N2) makes up 78% of the atmosphere, but most organisms can't use it directly.

* Nitrogen-fixing bacteria have the unique ability to convert atmospheric nitrogen into usable forms like ammonia (NH3) and nitrates (NO3-).

* These bacteria live in diverse environments, including:

* Soil: They form symbiotic relationships with plants (like legumes) or live freely in the soil.

* Water: They can be found in aquatic ecosystems.

* Some bacteria live inside the cells of certain organisms.

* The ammonia and nitrates produced by these bacteria become available to plants, which use them to build proteins, DNA, and other essential molecules.

* Animals then consume plants, obtaining their nitrogen from these food sources.

In summary, nitrogen-fixing bacteria play a crucial role in the nitrogen cycle, enabling the conversion of atmospheric nitrogen into usable forms for other living organisms.