Final answer:
Nitrogen fixation is a biological process performed by microorganisms using nitrogenase enzymes to convert atmospheric nitrogen into ammonia, a form usable by plants. This is essential for plant nutrition and the broader nitrogen cycle, improving agricultural yields.
Step-by-step explanation:
Nitrogen fixation is the process where certain microorganisms convert atmospheric nitrogen (N2) into biologically useful chemicals such as ammonia (NH3). These microorganisms utilize special enzymes called nitrogenases, which often contain iron and molybdenum, to catalyze this transformation. This phenomenon is crucial as plants cannot use free nitrogen gas directly but can absorb nitrogen when it's in the form of nitrates or ammonia.
Nitrogen-fixing bacteria, such as rhizobia, often form a symbiotic relationship with the root nodules of legumes to provide them with the necessary nitrogen in a usable form. The process of nitrogen fixation is essential for agricultural production since nitrogen is a key nutrient required by plants for the synthesis of nucleotides and proteins, thereby improving crop yields and competing against weeds.
In the broader nitrogen cycle, nitrogen-fixing bacteria play a pivotal role by converting atmospheric nitrogen into ammonia—this is referred to as ammonification. Then, through nitrification, other soil bacteria oxidize ammonia to nitrite and finally to nitrate, which plants can assimilate. Conversely, the process of converting nitrates back to nitrogen gas is termed denitrification and is also conducted by soil bacteria.