What is the role of prokaryotes in the nitrogen cycle?
Prokaryotes play a vital role in the nitrogen cycle, which is the process of converting
atmospheric nitrogen (N2) into various forms that can be utilized by living organisms.
These organisms include plants, animals, and other microbes. The nitrogen cycle is
divided into several steps that involve various types of prokaryotes.
The first step of the nitrogen cycle is nitrogen fixation, which is the conversion of
atmospheric nitrogen (N2) into ammonia (NH3). This is accomplished by nitrogenfixing bacteria such as Rhizobium and Azotobacter, which are commonly found in
the soil around plant roots. These bacteria convert nitrogen gas to ammonium ions,
which are then utilized by plants and other organisms.
The second step of the nitrogen cycle is nitrification, in which ammonia is converted
into nitrites (NO2-) and nitrates (NO3-). This process is carried out by nitrifying
bacteria such as Nitrosomonas and Nitrobacter. These bacteria decompose dead
organic matter to gain nitrogen, producing ammonium ions, which are then converted
into nitrites and nitrates.
The third step is denitrification, in which nitrate is converted back into atmospheric
nitrogen gas (N2). This process is carried out by denitrifying bacteria such as
Pseudomonas and Alcaligenes. These bacteria live in anaerobic environments, such
as sediments in bodies of water, and convert nitrate to N2 under low-oxygen
conditions.
Prokaryotes play a crucial role in the nitrogen cycle, as they are responsible for
converting atmospheric nitrogen into a form that can be utilized by other living
organisms. Without the help of prokaryotes, the nitrogen cycle would not function,
and life as we know it would not be sustained.
References:
1. Falkowski, P. G., Fenchel, T., & Delong, E. F. (2008). The microbial engines that drive
Earth's biogeochemical cycles. Science, 320(5879), 1034-1039.
2. Postgate, J. R. (1982). The nitrogen cycle. Cambridge University Press.
3. Ward, B. B., & Zafiriou, O. C. (1987). Nitrogen cycling in the ocean: New perspectives on
processes and paradigms. Oceanography, 57-69.