Nitrogenase is an enzyme complex found in certain bacteria and archaea that plays a crucial role in the nitrogen cycle. It catalyzes the conversion of atmospheric nitrogen gas (N2) into ammonia (NH3), a process known as nitrogen fixation. This transformation is essential for making nitrogen available to living organisms, as most cannot utilize atmospheric nitrogen directly. The nitrogenase enzyme requires a significant amount of energy, typically derived from ATP, and operates under anaerobic conditions, meaning it functions without oxygen. This makes nitrogenase vital for the growth of many plants, as it allows them to access nitrogen from the soil, promoting healthy development and crop yields.