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How do bacteria take part in the nitrogen cycle?
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Bacteria
A scanning electron micrograph of gram-positive Mycobacterium tuberculosis bacteria, the cause of tuberculosis and scrofula.
Bacteria are essential to the nitrogen cycle, a process that circulates nitrogen through nature and makes it available to living organisms. They facilitate several key transformations:1
- Nitrogen Fixation: More than 90 percent of nitrogen fixation is performed by nitrogen-fixing bacteria. These microorganisms convert atmospheric nitrogen gas into inorganic compounds like ammonia, which plants can use for growth. This includes free-living bacteria and mutualistic species that form symbiotic relationships with plants.21
- Nitrification: Nitrifying bacteria convert soil ammonia into nitrites and then into nitrates, which are forms of nitrogen that plants can readily assimilate.31
- Ammonification: Microorganisms decompose the remains and waste products of living things, yielding ammonia and ammonium.1
- Denitrification: Denitrifying bacteria convert nitrates in the soil back into atmospheric nitrogen. While this process can reduce soil fertility, it is vital for preventing the excessive accumulation of nitrogen in the oceans.41