1. Nitrogen fixation is the process of converting atmospheric nitrogen into nitrogenous salts, rendering it accessible to plants for uptake.
2. When living organisms participate in the nitrogen fixation process, it is termed biological nitrogen fixation.
3. Predominantly carried out by prokaryotic organisms, particularly various bacteria in the soil, biological nitrogen fixation is a crucial aspect of nitrogen cycling.
4. Organisms responsible for nitrogen fixation, referred to as diazotrophs or nitrogen fixers, play a vital role, contributing to approximately 70% of nitrogen fixation.
5. Nitrogen fixers can either be free-living bacteria or engage in symbiotic relationships with higher plants, such as the association between Rhizobium and certain plants.
6. Cyanobacteria, equipped with specialized cells known as heterocysts, actively participate in the nitrogen fixation process.
7. Nitrogen fixation demands a significant amount of energy, with approximately 16 ATP molecules required for the conversion of one nitrogen molecule into ammonia.
8. Soil bacteria, such as Nitrosomonas and Nitrobacter, facilitate nitrification—a biological oxidation process—by converting ammonia to nitrate and nitrite to nitrate, respectively.
9. These bacteria are chemoautotrophic, utilizing these nitrogen transformation processes as part of their metabolic activities.
10. Plants of the Fabaceae family, such as peas and beans, form root nodules housing the symbiotic bacterium Rhizobium, which actively fixes nitrogen in a host-specific manner, making nitrogen available to the host plant.