Desulfobacter hydrogenophilus
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| Desulfobacter hydrogenophilus | |
|---|---|
Scientific classification  | |
| Domain: | Bacteria |
| Kingdom: | Pseudomonadati |
| Phylum: | Thermodesulfobacteriota |
| Class: | Desulfobacteria |
| Order: | Desulfobacterales |
| Family: | Desulfobacteraceae |
| Genus: | Desulfobacter |
| Species: | D. hydrogenophilus |
| Binomial name | |
| Desulfobacter hydrogenophilus Widdell, 1987 | |
Desulfobacter hydrogenophilus is a strictly anaerobic sulfate-reducing bacterium.[1] It was isolated and characterized in 1987 by Friedrich Widdel of the University of Konstanz (Germany). Like most sulfate-reducing bacteria (SRB), D. hydrogenophilus is capable of completely oxidizing organic compounds (specifically acetate, pyruvate and ethanol) to CO2, and therefore plays a key role in biomineralization in anaerobic marine environments.[2] However, unlike many SRB, D. hydrogenophilus is a facultative lithoautotroph, and can grow using H2 as an electron donor and CO2 as a carbon source.[1] D. hydrogenophilus is also unique because it is psychrophilic (and has been shown to grow at temperatures as low as 0 °C or 32 °F). It is also diazotrophic, or capable of fixing nitrogen.[1]
Cells are elongated-oval shaped, and 1–1.3 by 2–3 μm in size. They are non-motile, gram-negative, and non-sporulating.[1]
Metabolism
Desulfobacter hydrogenophilus is the only described species of Desulfobacter that can grow chemolithoautotrophically.[3] Using H2 as an electron donor and CO2 as a carbon source, D. hydrogenophilus reduces sulfate, SO42− (and also sulfite, SO32−, and thiosulfate, S2O32−) to sulfide, S2−.[1] However, D. hydrogenophilus is a facultative lithoautotroph, and may also use acetate, pyruvate, or ethanol as both an electron donor and carbon source.[1] A modified tricarboxylic acid (TCA) cycle is employed for acetate metabolism and autotrophic growth.[4] When D. hydrogenophilus is grown with either H2 or acetate, doubling time is less than 30 hours, but when grown with pyruvate or ethanol, doubling time is over 30 hours. The shortest doubling time observed on acetate was 18 hours.[1]
Butyrate cannot be used as an electron donor, and neither elemental sulfur, S0, nor nitrate, NO3−, can be used as electron acceptors.[1] Fermentative growth has not been observed.[1]
Diazotrophic growth was observed in D. hydrogenophilus.[1] Other Desulfobacter strains have also exhibited diazotrophic growth, but D. hydrogenophilus has exhibited the fastest diazotrophic growth rates of all the strains. D. hydrogenophilus’ doubling time with N2 as the nitrogen source was 36 hours, whereas other strains grew with a doubling time of 50 hours or more.[1]
Ecology
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The strain AcRS1, which was isolated for the enrichment culture used to describe the species in 1986, was taken from Rio di San Giacomo in Venice, Italy.[1]
Desulfobacter hydrogenophilus is most commonly found in anoxic brackish or marine sediments, but has also been found in anoxic freshwater sediments and in activated sludge.[3]
Desulfobacter hydrogenophilus is ecologically unique in that it has a wide temperature and pH range. Unlike any other species in its genus, D. hydrogenophilus is psychrophilic, or capable of growth and reproduction at cold temperatures.[1] Slow growth on acetate with a doubling time of 5 weeks still occurred at 0 °C in an ice water bath.[1] Its optimum growth temperature is 29–32 °C (84–90 °F), but growth occurs at temperatures of 0–35 °C (32–95 °F).[1] Optimum pH is 6.6–7.0, but growth occurs at pH values of 5.5–7.6.[1]