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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Denitrifying bacteria | 2/2 | https://en.wikipedia.org/wiki/Denitrifying_bacteria | reference | science, encyclopedia | 2026-05-05T09:00:55.402407+00:00 | kb-cron |
=== Role of denitrifying bacteria as a methane sink === Denitrifying bacteria have been found to play a significant role in the oxidation of methane (CH4) (where methane is converted to CO2, water, and energy) in deep freshwater bodies of water. This is important because methane is the second most significant anthropogenic greenhouse gas, with a global warming potential 25 times more potent than that of carbon dioxide, and freshwaters are a major contributor of global methane emissions. A study conducted on Europe's Lake Constance found that anaerobic methane oxidation coupled to denitrification – also referred to as nitrate/nitrite-dependent anaerobic methane oxidation (n-damo) – is a dominant sink of methane in deep lakes. For a long time, it was considered that the mitigation of methane emissions was only due to aerobic methanotrophic bacteria. However, methane oxidation also takes place in anoxic, or oxygen depleted zones, of freshwater bodies. In the case of Lake Constance, this is carried out by M. oxyfera-like bacteria. M. oxyfera-like bacteria are bacteria similar to Candidatus Methylomirabilis oxyfera, which is a species of bacteria that acts as a denitrifying methanotroph. The results from the study on Lake Constance found that nitrate was depleted in the water at the same depth as methane, which suggests that methane oxidation was coupled to denitrification. It could be inferred that it was M. oxyfera-like bacteria carrying out the methane oxidation because their abundance peaked at the same depth where the methane and nitrate profiles met. This n-damo process is significant because it aids in decreasing methane emissions from deep freshwater bodies and it aids in turning nitrates into nitrogen gas, reducing excess nitrates.
== Denitrifying bacteria and the environment ==
=== Denitrification effects on limiting plant productivity and producing by-products === The process of denitrification can lower the fertility of soil as nitrogen, a growth-limiting factor, is removed from the soil and lost to the atmosphere. This loss of nitrogen to the atmosphere can eventually be regained via introduced nutrients, as part of the nitrogen cycle. Some nitrogen may also be fixated by species of nitrifying bacteria and the cyanobacteria. Another important environmental issue concerning denitrification is the fact that the process tends to produce large amounts of by-products. Examples of by-products are nitric oxide (NO) and nitrous oxide (N2O). NO is an ozone depleting species and N2O is a potent greenhouse gas which can contribute to global warming.
=== Denitrifying bacteria use in wastewater treatment === Denitrifying bacteria are an essential component in treating wastewater. Wastewater often contains large amounts of nitrogen (in the form of ammonium or nitrate), which could be damaging to ecological processes if left untreated. Many physical, chemical, and biological methods have been used to remove the nitrogenous compounds and purify wastewaters. The process and methods vary, but it generally involves converting ammonium to nitrate via the nitrification process with ammonium oxidizing bacteria (AOB, NH4+ → NO2–) and nitrite oxidizing bacteria (NOB, NO2– → NO3–), and finally to nitrogen gas via denitrification. One example of this is ammonia-oxidizing bacteria which have a metabolic feature that, in combination with other nitrogen-cycling metabolic activities, such as nitrite oxidation and denitrification, remove nitrogen from wastewater in activated sludge. Since denitrifying bacteria are heterotrophic, an organic carbon source is supplied to the bacteria in an anoxic basin. With no available oxygen, denitrifying bacteria use the redox of nitrate to oxidize the carbon. This leads to the creation of nitrogen gas from nitrate, which then bubbles up out of the wastewater.
== See also == Nitrifying bacteria Nitrogen Cycle
== References ==