Thermodesulfobacteriota
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The Thermodesulfobacteriota, or Desulfobacterota,<ref name=":0">Template:Cite journal</ref> are a phylum of anaerobic Gram-negative bacteria. Many representatives are sulfate-reducing bacteria,<ref>Template:Cite journal</ref> others can grow by disproportionation of various sulphur species,<ref name=":1">Template:Cite journal</ref> reduction or iron,<ref>Template:Cite journal</ref> or even use external surfaces as electron acceptors (exoelectrogens).<ref name=":2">Template:Cite journal</ref> They have highly variable morphology: vibrio, rods, cocci,<ref name=":0" /> as well as filamentous cable bacteria.<ref name=":4">Template:Cite journal</ref> Individual members of Desulfobacterota are also studied for their bacterial nanowires<ref name=":5" /> or syntrophic relationships.<ref name=":3" />
TaxonomyEdit
The bacterial phylum Desulfobacterota has been created by merging: 1) the well-established class Thermodesulfobacteria, 2) the proposed phylum Dadabacteria, and 3) various taxa separated from the abandoned non-monophyletic class "Deltaproteobacteria" alongside three other phyla: Myxococcota, Bdellovibrionota, and SAR324.<ref name=":0" />
EnvironmentEdit
In contrast to their close relatives, the aerobic phyla Myxococcota and Bdellovibrionota, Desulfobacterota are predominantly anaerobic.<ref name=":0" /> They likely retained their anaerobic lifestyle since before the Great Oxidation Event.<ref>Template:Citation</ref>
Three closely related classes within Desulfobacterota: Thermodesulfobacteria, Dissulfuribacteria, and Desulfofervidia,<ref name=":3">Template:Cite journal</ref> as well as the more distant Deferrisomatia, are exclusively thermophilic, while most members of other classes are mesophiles<ref name=":0" /> or even psychrophiles.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
MetabolismEdit
Sulfate-reducing bacteria (SRB) utilize sulfate as a terminal electron acceptor in a respiratory-type metabolism, coupled to the oxidation of organic compounds or hydrogen. By reducing sulfate, many Desulfobacterota species substantially contribute to the sulfur cycle.<ref name=":0" />
Microbial sulfur disproportionation (MSD) is a poorly known type of energy metabolism analogous to organic fermentation, where a single inorganic sulfur species of intermediate oxidation state is simultaneously oxidized and reduced, resulting in production of sulfide and sulfate. In Desulfobacterota, MSD is often present in species that also perform sulfate reduction.<ref name=":1" />
Sulfur oxidation is rare among Desulfobacterota.<ref name=":6">Template:Cite journal</ref> However, several strains are known to perform this type of metabolism using diverse mechanisms. Strain MLMS-1 couples oxidation of sulfide to reduction of arsenate.<ref>Template:Cite journal</ref> Dissulfuribacter thermophilus (Dissulfuribacteria) oxidizes elemental sulfur with dissimilatory nitrate reduction to ammonium.<ref>Template:Cite journal</ref> Desulfurivibrio alkaliphilus (Desulfobulbia) couples oxidation of sulfide to the dissimilatory reduction of nitrate and nitrite to ammonium.<ref name=":6" /> Cable bacteria, closely related to D. alkaliphilus, oxidize sulfide using a long-distance electron transport to oxygen or nitrate reduction — see below.<ref>Template:Cite journal</ref>
Fe(III) minerals can be microbially reduced by Fe-reducing bacteria (FeRB) using a wide range of organic compounds or H2 as electron donors. FeRB are widespread across Bacteria. Among Desulfobacterota, they are represented e.g. by the genus Geobacter (Desulfuromonadia).<ref>Template:Cite journal</ref>
Certain species of the families Geobacteraceae and Desulfuromonadaceae (Desulfuromonadia) are able to use external surfaces as electron acceptors to complete respiration.<ref name=":2" /><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Species of the genus Geobacter use bacterial nanowires to transfer electrons to extracellular electron acceptors such as Fe(III) oxides.<ref name=":5">Template:Cite journal</ref>
Certain species of the class Syntrophia use simple organic molecules as electron donors and grow only in the presence of H2/formate-utilizing partners (methanogens or Desulfovibrio) in syntrophic associations.<ref>Template:Citation</ref>
The family Desulfobulbaceae contains two genera of cable bacteria: Ca. Electronema and Ca. Electrothrix. These filamentous bacteria conduct electricity across distances over 1 cm, which allows them to connect distant sources of electron donors and electron acceptors.<ref name=":4" />
- Cable bacteria in sediment.png
Cable bacteria in between two layers of sediment
- Cable diagram.svg
Diagram demonstrating cable bacteria metabolism in surface sediment
- Model representation of a cable bacteria cell.jpg
Model representation of a cable bacteria cell
Notable speciesEdit
- Desulfobulbus propionicus (Desulfobulbia), described in 1982 from mud samples in Germany, can serve as a biocatalyst in microbial electrosynthesis, i.e. the usage of electrons by microorganism to reduce carbon dioxide to organic molecules.<ref>Template:Cite journal</ref>
- Lawsonia intracellularis (Desulfovibrionia), described in 1995 from the intestines of pigs with proliferative enteropathy disease, is a highly pathogenic intracellular parasite.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
- Oleidesulfovibrio alaskensis (Desulfovibrionia), described in 2004 from an oil well in Alaska, corrodes metals and reduces toxic radionuclides and metals such as uranium and chromium to less soluble and less toxic forms.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
- Syntrophorhabdus aromaticivorans (Syntrophorhabdia), described in 2008 from industrial wastewater, is the first cultured anaerobe capable of degrading phenol to acetate in obligate syntrophic associations with a hydrogenotrophic methanogen.<ref>Template:Cite journal</ref>
- Dissulfuribacter thermophilus (Dissulfuribacteria), described in 2013 from a deep-sea hydrothermal vent, does not reduce sulfate and instead disproportionates elemental sulfur and other intermediate sulfur species.<ref>Template:Cite journal</ref>
- Ca. Desulfofervidus auxilii (Ca. Desulfofervidia), described in 2016 from Guaymas Basin sediments, is involved in the anaerobic oxidation of methane (AOM) together with archaeal syntrophic partners.<ref name=":3" />
MicroscopyEdit
- Thermodesulfobacterium hveragerdense JSP.jpg
- Dvulgaris micrograph.JPG
- Caldimicrobium rimae.jpg
- Thermodesulfobacterium hydrogeniphilum.jpg
- Cell morphology of Dissulfuribacter thermophilus strain S69.gif
- Thermodesulfatator indicus CIR 29812.jpg
- Thermosulfurimonas dismutans.jpg
- Thermodesulfobacterium commune.jpg
- Thermodesulfatator atlanticus.jpg
- Thermosulfuriphilus ammonigenes.jpg
- Desulfovibrio alaskensis cells on stainless steel 304.jpg
- Electronema candidate specie.jpg
Ca. Electronema sp.
- Mouse gut-derived taurine-respiring strain LT0009 that represents Taurinivorans muris.jpg
- 41467 2023 41008 Fig1c-FISH.jpg
- Proposal of catalyzing bio-voltage memristors.webp
Geobacter sulfurreducens and its bacterial nanowires<ref>Template:Cite journal</ref>
- Geobacter sulfurreducens.TIF
PhylogenyEdit
Template:See also The phylogeny is based on phylogenomic analysis:
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See alsoEdit
- Sulfur cycle
- Exoelectrogen
- Cable bacteria
- Syntrophy
- Thermophile
- Bacterial nanowires
- Sulfate reducing bacteria
ReferenceEdit
Template:ReflistTemplate:Bacteria classification Template:Life on Earth Template:Taxonbar