from the sulfate reduction activity in the sediments. This process is also considered a major sink for sulfate in marine sediments. In hydraulic fracturing, fluids are used to frack shale formations to recover methane (shale gas) and hydrocarbons. Biocide compounds are often added to water to inhibit the microbial activity of sulfate-reducing microorganisms, in order to but not limited to, avoid anaerobic methane oxidation and the generation of hydrogen sulfide, ultimately resulting in minimizing potential production loss. Biochemistry Before sulfate can be used as an electron acceptor, it must be activated. This is done by the enzyme ATP-sulfurylase, which uses ATP and sulfate to create adenosine 5′-phosphosulfate (APS). APS is subsequently reduced to sulfite and AMP. Sulfite is then further reduced to sulfide, while AMP is turned into ADP using another molecule of ATP. The overall process, thus, involves an investment of two molecules of the energy carrier ATP, which must to be regained from the reduction. The enzyme dissimilatory (bi)sulfite reductase, dsrAB (EC 1.8.99.5), that catalyzes the last step of dissimilatory sulfate reduction, is the functional gene most used as a molecular marker to detect the presence of sulfate-reducing microorganisms. Phylogeny The sulfate-reducing microorganisms have been treated as a phenotypic group, together with the other sulfur-reducing bacteria, for identification purposes. They are found in several different phylogenetic lines. As of 2009, 60 genera containing 220 species of sulfate-reducing bacteria are known. Among the Thermodesulfobacteriota the orders of sulfate-reducing bacteria include Desulfobacterales, Desulfovibrionales, and Syntrophobacterales. This accounts for the largest group of sulfate-reducing bacteria, about 23 genera. The second largest group of sulfate-reducing bacteria is found among the Bacillota, including the genera Desulfotomaculum, Desulfosporomusa, and Desulfosporosinus. In the Nitrospirota phylum we find sulfate-reducing Thermodesulfovibrio species. Two more groups that include thermophilic sulfate-reducing bacteria are given their own phyla, the Thermodesulfobacteriota and Thermodesulfobium. There are also three known genera of sulfate-reducing archaea: Archaeoglobus, Thermocladium and Caldivirga. They are found in hydrothermal vents, oil deposits, and hot springs. In July 2019, a scientific study of Kidd Mine in Canada discovered sulfate-reducing microorganisms living below the surface. The sulfate reducers discovered in Kidd Mine are lithotrophs, obtaining their energy by oxidizing minerals such as pyrite rather than organic compounds. Kidd Mine is also the site of the oldest known water on Earth. See also Anaerobic respiration Deep biosphere Extremophile Microbial metabolism Microorganism Quinone-interacting membrane-bound oxidoreductase Sulfur cycle References External links 'Follow the Water':