Desulfobacterales are an order of sulfate-reducing bacteria within the phylum Thermodesulfobacteria. The order contains three families; ''Desulfobacteraceae, Desulfobulbaceae'', and ''Nitrospinaceae''. The bacterium in this order are strict anaerobic respirators, using sulfate or nitrate as the terminal electron acceptor instead of oxygen. Desulfobacterales can degrade ethanol, molecular hydrogen, organic acids, and small hydrocarbons. The bacterium of this order have a wide ecological range and play important environmental roles in symbiotic relationships and nutrient cycling.

Habitat

Desulfobacterales are found globally and often in extreme environments, such as deep-sea hydrothermal vents,

hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by c ...

s, marine sediment, and solfataric fields, an area of volcanic venting that gives off sulfurous gases.

Symbiotic Relationships

Sulfate-reduction by ''Desulfobacteraceae'' and ''Desulfobulbaceae'' in coastal marine sediments plays an important role in molecular hydrogen cycling through a close relationship with fermenting microorganisms.

Fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

microbes break down organic materials on the seafloor and produce molecular oxygen and organic acids. Molecular hydrogen is an essential electron donor used by Desulfobacterales; they use the molecular hydrogen produced by fermentation to drive sulfate reduction. This feedback loop maintains molecular hydrogen at an energetically favorable level for fermenting respiration and provides ample molecular hydrogen for sulfate reduction.

Nitrogen Cycling

Pathways for the nitrogen cycle in mangrove forests

Human activity, such as increased fertilizer use, has caused nitrogen pollution in inland and coastal waters. An influx of nitrogen inputs into aquatic ecosystems can cause negative effects such as

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

, resulting in anoxic conditions. Desulfobacterales are important in nitrogen pollution mitigation in coastal mangrove ecosystems through nitrate reduction. Nitrate is reduced by Desulfobacterales species via dissimilatory nitrate reduction genes. Dissimilatory nitrate reduction accounts for roughly 75.7–85.9% of nitrate reduction in mangrove ecosystems. Dissimilatory nitrate reduction is important because nitrate is reduced to ammonium, which can then be taken up by other microorganisms and plants in the system.

References

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