Desulfobacter hydrogenophilus

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Classification

  • Domain: Bacteria
  • Phylum: Proteobacteria
  • Class: Deltaproteobacteria
  • Order: Desulfobacterales
  • Family: Desulfobacteraceae
  • Genus: Desulfobacter
  • Species: hydrogenophilus

Description

This particular microbe was first discovered and isolated in pure culture at the University of Konstanz by Friedrich Widdel in 1987 [1]. The organism is most well known for its sulfate reducing capabilities. The species is Gram-negative, ovoid in form, and is typically 1-3 µm long. Among the other species of the Desulfobacter genus, this species is highly related to its two sister species: Desulfobacter latus and Desulfobacter curvatus. Interestingly enough, these two species were also discovered by Widdel in the same paper that discovered Desulfobacter hydrogenophilus.

Ecology and Significance

Desulfobacter hydrogenophilus plays an important role within the ecology of water systems. Its most important function (reducing sulfate into sulfide) plays a large part in the sulfur cycle in lakes, bays, and other aquatic sediments. In the case of the Winogradsky column, this bacteria produces the H2S that is used by both the green and purple sulfur bacteria. This is rather similar to the role it takes on in the ecosystem of lakes.

Interestingly enough, this species is capable of living in a wide range of environments. Although it was found in the Mediterranean Sea, it has been documented in both marine and freshwater environments[3]. Additionally, due to its psychrophilic nature, this organism is capable of growing at much colder temperatures than other SRBs, widening its niche.

Desulfobacter hydrogenophilus also has uses in wastewater treatment processes. Not only is the species able to degrade carbon into simpler forms, but it can also provide different forms of sulfur to the other microbes present in the sludge.

Genome Structure

The genome of Desulfobacter hydrogenophilus has a 45% GC content[1]. The most studied part of the genome for this species are the genes that encode the sulfate reducing abilities of this bacteria. However, other interesting genes have been found in this species. Studies have found that this species contains enzymes necessary for nitrogen fixation. Additionally, this species uses an interesting method of fixing carbon. Instead of using the Calvin cycle or the acetyl CoA pathway, Desulfobacter hydrogenophilus was found to have genes encoding a unique reductive citric acid cycle as a means of fixing CO2[2].

Metabolism

Desulfobacter hydrogenophilus is best known for its sulfur reducing capabilities. It is capable of reducing sulfate, sulfite, and thiosulfate when coupled to the oxidation of organic carbons like acetate[4]. Unlike the rest of its genus, this species is capable of facultative chemolithoautotrophy. This is done by coupling CO2 fixation with the reduction of sulfate and the oxidation of H2. This unique mechanism allows the species to utilize the best pathway for maximum growth in a particular environment. As mentioned previously, carbon fixation occurs through unique reductive citric acid cycle in this species.

In addition to energy source metabolism, Desulfobacter hydrogenophilus is also able to fix nitrogen gas into organic nitrogen, giving it an advantage over species that depend on nitrogen fixers.

References

1: F. Widdel (1987). "New types of acetate-oxidizing, sulfate-reducing Desulfobacter species, D. hydrogenophilus sp. nov., D. latus sp. nov., and D. curvatus sp. nov.". Archives of Microbiology 148 (4): 286–291.

2: F. Widdel (1987). "Carbon assimilation pathways in sulfate-reducing bacteria II. Enzymes of a reductive citric acid cycle in the autotrophic Desulfobacter hydrogenophilus." Archives of Microbiology 148 (3): 218-225.

3: G. Garrity (2005). Bergey's Manual of Systematic Bacteriology 2nd Edition. New York: Springer.

4: K.L. Londry et. al (2003). "Stable carbon isotope fractionation by sulfate-reducing bacteria". Applied and Environmental Microbiology 69 (5): 2942–2949.


Author

Page authored by Nicholas Rogall, student of Prof. Katherine Mcmahon at University of Wisconsin - Madison.