Editing Nitrogen cycle (section)

=== Denitrification ===
{{Main|Denitrification}}
Denitrification is the reduction of nitrates back into nitrogen gas ({{chem|N|2}}), completing the nitrogen cycle. This process is performed by bacterial species such as ''[[Pseudomonas]]'' and [[Paracoccus denitrificans|''Paracoccus'']], under anaerobic conditions. They use the nitrate as an electron acceptor in the place of oxygen during respiration. These facultatively (meaning optionally) anaerobic bacteria can also live in aerobic conditions. Denitrification happens in anaerobic conditions e.g. waterlogged soils. The denitrifying bacteria use nitrates in the soil to carry out respiration and consequently produce nitrogen gas, which is inert and unavailable to plants. Denitrification occurs in free-living microorganisms as well as obligate symbionts of anaerobic ciliates.<ref>{{cite journal |last1=Graf |first1=Jon S. |last2=Schorn |first2=Sina |last3=Kitzinger |first3=Katharina |last4=Ahmerkamp |first4=Soeren |last5=Woehle |first5=Christian |last6=Huettel |first6=Bruno |last7=Schubert |first7=Carsten J. |last8=Kuypers |first8=Marcel M. M. |last9=Milucka |first9=Jana |title=Anaerobic endosymbiont generates energy for ciliate host by denitrification |journal=Nature |date=3 March 2021 |volume=591 |issue=7850 |pages=445–450 |doi=10.1038/s41586-021-03297-6| issn=0028-0836|pmid=33658719 |pmc=7969357 |bibcode=2021Natur.591..445G |doi-access=free }}</ref>

<gallery mode=packed style=float:left heights=270px>
File:Nitrogen cycle.jpg| Classical representation of nitrogen cycle
File:Nitrogen Cycle 2.svg|alt=Diagram of nitrogen cycle above and below ground. Atmospheric nitrogen goes to nitrogen-fixing bacteria in legumes and the soil, then ammonium, then nitrifying bacteria into nitrites then nitrates (which is also produced by lightning), then back to the atmosphere or assimilated by plants, then animals. Nitrogen in animals and plants become ammonium through decomposers (bacteria and fungi).|Flow of nitrogen through the ecosystem. Bacteria are a key element in the cycle, providing different forms of nitrogen compounds able to be assimilated by higher organisms
</gallery>

<gallery mode=packed style=float:right heights=400px>
File:The Nitrogen Cycle.png| Simple representation of the nitrogen cycle. Blue represent nitrogen storage, green is for processes moving nitrogen from one place to another, and red is for the bacteria involved
</gallery>

{{clear left}}