What is the process that involves the transformation of nitrogen gas into a usable form by bacteria?

In the context of the nitrogen cycle, the process that transforms nitrogen gas (N₂) into a usable form—specifically ammonia (NH₃) or related compounds—is known as nitrogen fixation. This process is primarily facilitated by certain types of bacteria, including free-living bacteria as well as those that have symbiotic relationships with the roots of some plants (like legumes).

During nitrogen fixation, atmospheric nitrogen is converted into ammonia, which can then be taken up by plants. This is crucial because most living organisms cannot use nitrogen gas directly; they require nitrogen in a fixed form. Once nitrogen is fixed, it can enter the food web as plants utilize it for growth, ultimately supporting various forms of life.

Understanding nitrogen fixation is key to grasping the broader concept of nutrient cycling in ecosystems, as it highlights how essential elements are transformed and made available for biological processes.