What is nitrogen fixation?
Nitrogen fixation(a primary step of the nitrogen cycle ) is fixation of nitrogen into amino acids by nitrogen fixing bacteria.
Plants can't utilize the atmospheric nitrogen directly. Certain legume
plants(i.e pea, bean) are hosts of symbionts bacteria (Nitrogen fixing
bacteria) . These bacteria inhabit the roots of these plants and form
root nodules. These root nodules bacteria then fix the nitrogen in the soil air to amino acids. This process is called nitrogen fixation.
These amino acids are then utilized by plants (hosts). In return plants provide protection and food to bacteria.