Geoalkalibacter subterraneus

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G. subterraneus centrifuged in FRR medium.

Classification

Phylogenetic tree of strain Red1T and its closest relatives. Constructed from 16SrRNA. Bar, 2 nucleotide exchanges per 100 nucleotides.

Higher order taxa

Bacteria; Proteobacteria; Deltaproteobacteria; Desulfuromonadales; Geobacteraceae

Species

Geoalkalibacter subterraneus

Description and Significance

Geoalkalibacter subterraneus is a gram-negative motile rod with polar flagella. G. subterraneus does not form spores. The species forms biofilms. Cells range in length 1.0-5.0µm, and diameter .5-.6µm.

Electron micrograph of strain Red1T showing the short rod shape and flagella (arrow). Bar, 0.2 μm.

Genome Structure

Geoalkalibacter subterraneus has one circular chromosome and one plasmid, both have been completely sequenced for strain Red1T[1] The chromosome contains 3.48Mb, 3287 genes and 3202 coding genes with 57.0%GC. The plasmid contains 242Kb, 258 genes and 256 coding genes with 51.4%GC.

Cell Structure, Metabolism and Life Cycle

G. subterraneus is strictly anaerobic. It obtains energy by reducing a variety of oxidized species including Fe(III), Mn(IV), nitrate, elemental sulfur and trimethylamine N-oxide; in the presence of a wide range of electron donors including; acetate, butyrate, isobutyrate, citrate, decanoate, dodecanoate, ethanol, formate, fumarate, glycerol, hydrogenlactate, malonate, methanol, octanoate, palmitate, p-anisate, peptone, propionate, pyruvate, salicylate, stearate, succinate, valerate, isovalerate and yeast extract. G. subterraneus grows optimally at 40°C, pH 7 and salinity 20g/L. G. subterraneus can grow between temperatures 30-50°C, salinity between 1-100g/L, and pH 6-9.

Ecology

Representative strain Red1T was isolated from Redwash oilfield Utah, USA at a depth of 1540 m at 52 °C. The salinity level was measured to be 25g/L with pH of 7.9. Unlike close relatives, G. subterraneus is alkalitolerant and has a maximum growth rate close to pH 7. It is unknown whether or not G. subterraneus is indigenous to oil reservoirs. A closely related strain has been detected in an oil well in Malaysia in similar conditions. The strain may have been introduced to Redwash oilfield through the water flooding process[2] during secondary recovery, as the closest relatives to G. subterraneus are endemic to rivers, and Redwash oilfield was specifically flooded with river water.

G. subterraneus forms biofilms which may be important for long range electron transfer between cells.

3D reconstruction of CLSM slices of a Geoalkalibacter subterraneus biofilm.

References

Greene, A., Patel, B., and Yacob, S. "Geoalkalibacter subterraneus sp. nov., an anaerobic Fe(III) and Mn(IV) reducing bacterium from a petroleum reservoir, and emended descriptions of the family Desulfuromonadaceae and the genus Geoalkalibacter." International Journal of Systematic and Evolutionary Microbiology. 2009. Volume 59. p. 781–785.

Carmona-Martínez, A., Pierra, M., Trably, E., and Bernet, N. "High current density via direct electron transfer by the halophilic anode respiring bacterium Geoalkalibacter subterraneus." Physical Chemistry Chemical Physics. 2013. Volume 15. p. 19699-19707.

Li, D., Midgley, D., Ross, J., Oytam, Y., Abell, G., Volk, H., Daud, W., Hendry, P. "Microbial biodiversity in a Malaysian oil field and a systematic comparison with oil reservoirs worldwide." Archives of Microbiology. 2012. Volume 194. p. 513-523.

Author

Page authored by Luke Pryke and Hannah Pak, students of Prof. Jay Lennon at Indiana University.