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Twenty-five samples of stratal fluids obtained from a high-temperature (60-84 degrees C) deep subsurface (1700-2500 m) petroleum reservoir of Western Siberia were investigated for the presence of dissimilatory Fe(III)-reducing microorganisms. Of the samples, 44% and 76% were positive for Fe(III) reduction with peptone and H2 respectively as electron donors. In most of these samples, the numbers of culturable thermophilic H2-utilizing iron reducers were in the order of 10-100 cells/ml. Nine strains of thermophilic anaerobic bacteria and archaea isolated from petroleum reservoirs were tested for their ability to reduce Fe(III). Eight strains belonging to the genera Thermoanaerobacter, Thermotoga, and Thermococcus were found capable of dissimilatory Fe(III) reduction, with peptone or H2 as electron donor and amorphous Fe(III) oxide as electron acceptor. These results demonstrated that Fe(III) reduction may be a common feature shared by a wide range of anaerobic thermophiles and hyperthermophiles in deep subsurface petroleum reservoirs.http://link.springer-ny. com/link/service/journals/00284/bibs/39n2p99.html

A strain of a thermophilic, anaerobic, dissimilatory, Fe(II1)-reducing bacterium, Thennoterrabacterium ferrireducens gen. nov., sp. nov. (type strain JW/AS-Y7T; DSM 11255), was isolated from hot springs in Yellowstone National Park and New Zealand. The gram-positive-staining cells occurred singly or in pairs as straight to slightly curved rods, 0.3 to 0.4 by 1.6 to 2.7 pm, with rounded ends and exhibited a tumbling motility. Spores were not observed. The temperature range for growth was 50 to 74°C with an optimum at 65°C. The pH range for growth at 65°C was from 5.5 to 7.6, with an optimum at 6.0 to 6.2. The organism coupled the oxidation of glycerol to reduction of amorphous Fe(II1) oxide or Fe(II1) citrate as an electron acceptor. In the presence as well as in the absence of Fe(II1) and in the presence of CO,, glycerol was metabolized by incomplete oxidation to acetate as the only organic metabolic product; no H, was produced during growth. The organism utilized glycerol, lactate, 1,2-propanediol, glycerate, pyruvate, glucose, fructose, mannose, and yeast extract as substrates. In the presence of Fe(II1) the bacterium utilized molecular hydrogen. The organism reduced 9,10-anthraquinone-2,6-disulfonic acid, fumarate (to succinate), and thiosulfate (to elemental sulfur) but did not reduce MnO,, nitrate, sulfate, sulfite, or elemental sulfur. The G+C content of the DNA was 41 mol% (as determined by high-performance liquid chromatography). The 16s ribosomal DNA sequence analysis placed the isolated strain as a member of a new genus within the gram-type-positive Bacillus-Clostridium subphylum.

Thermosulfurimonas dismutans gen. nov., sp. nov., an extremely thermophilic sulfur-disproportionating bacterium from a deep-sea hydrothermal vent An extremely thermophilic, anaerobic, chemolithoautotrophic bacterium (strain S95 T ) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Center, Pacific Ocean, at a depth of 1910 m. Cells of strain S95 T were oval to short Gram-negative rods, 0.5-0.6 mm in diameter and 1.0-1.5 mm in length, growing singly or in pairs. Cells were motile with a single polar flagellum. The temperature range for growth was 50-92 6C, with an optimum at 74 6C. The pH range for growth was 5.5-8.0, with an optimum at pH 7.0. Growth of strain S95 T was observed at NaCl concentrations ranging from 1.5 to 3.5 % (w/v). Strain S95 T grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO 2 as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline iron(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain S95 T was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the phylum Thermodesulfobacteria. On the basis of its physiological properties and results of phylogenetic analyses, it is proposed that the isolate represents the sole species of a new genus, Thermosulfurimonas dismutans gen. nov., sp. nov.; S95 T (5DSM 24515 T 5VKM B-2683 T ) is the type strain of the type species. This is the first description of a thermophilic microorganism that disproportionates elemental sulfur.Biogeochemical cycling of sulfur in aquatic environments includes the activities of different aerobic and anaerobic prokaryotes. Bacteria that disproportionate sulfur compounds such as thiosulfate or elemental sulfur (Bak & Cypionka, 1987;Thamdrup et al., 1993) are a unique group of sulfur cycle micro-organisms. Sulfur isotope data from early Archaean rocks and the presence of microfossils in 3.4-billion-year-old geological formations suggest that sulfur disproportionation could be one of the earliest modes of microbial metabolism (Philippot et al., 2007;Wacey et al., 2011). Inorganic sulfur fermentation has been reported for members of the mesophilic genera Desulfovibrio, Desulfobulbus, Desulfocapsa, Desulfonatronum, Desulfonatronospira and Desulfonatronovibrio in the Deltaproteobacteria (Bak & Pfennig, 1987;Lovley & Phillips, 1994;Janssen et al., 1996;Pikuta et al., 2003;Sorokin et al., 2008 Sorokin et al., , 2011. Among thermophiles, Desulfotomaculum thermobenzoicum is the only micro-organism that has been reported to be capable of growth by thiosulfate disproportionation (Jackson & McInerney, 2000). Prior to this report, no thermophiles were known to disproportionate elemental sulfur. S 0 is abundant in thermal ecosystems, including deep-sea hydrothermal vents, where it forms when hydrogen sulfide-rich hydrothermal fluid mixes w...

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A hyperthermophilic, anaerobic, dissimilatory Fe(III)-reducing, facultatively chemolithoautotrophic archaeon (strain SBH6 T ) was isolated from a hydrothermal sample collected from the deepest of the known World Ocean hydrothermal fields, Ashadze field (126 589 210 N 446 519 470 W) on the Mid-Atlantic Ridge, at a depth of 4100 m. The strain was enriched using acetate as the electron donor and Fe(III) oxide as the electron acceptor. Cells of strain SBH6 T were irregular cocci, 0.3-0.5 mm in diameter. The temperature range for growth was 50-85 6C, with an optimum at 81 6C. The pH range for growth was 5.0-7.5, with an optimum at pH 6.8. Growth of SBH6 T was observed at NaCl concentrations ranging from 1 to 6 % (w/v) with an optimum at 2.5 % (w/v). The isolate utilized acetate, formate, pyruvate, fumarate, malate, propionate, butyrate, succinate, glycerol, stearate, palmitate, peptone and yeast extract as electron donors for Fe(III) reduction. It was also capable of growth with H 2 as the sole electron donor, CO 2 as a carbon source and Fe(III) as an electron acceptor without the need for organic substances. Fe(III) [in the form of poorly crystalline Fe(III) oxide or Fe(III) citrate] was the only electron acceptor that supported growth. 16S rRNA gene sequence analysis revealed that the closest relative of the isolated organism was Geoglobus ahangari 234 T (97.0 %). On the basis of its physiological properties and phylogenetic analyses, the isolate is considered to represent a novel species, for which the name Geoglobus acetivorans sp. nov. is proposed. The type strain is SBH6 T (5DSM 21716 T 5VKM B-2522 T ).Iron minerals are abundant in deep-sea hydrothermal vents. The surfaces of active chimneys are frequently covered with deposits of iron oxides in different oxidative states, and the amount of iron in hydrothermal fluid can reach molar concentrations. Thus, deep-sea hydrothermal vents can provide an ecological niche for Fe(III)-reducing micro-organisms (Slobodkin et al., 2001). However, only a few thermophilic Fe(III)-reducers have been isolated from this environment. Currently, thermophilic and hyperthermophilic iron-reducing micro-organisms recovered from deep-sea habitats include two species of the Bacteria, Geothermobacter ehrlichii (Kashefi et al., 2003) and Deferribacter abyssi (Miroshnichenko et al., 2003), and three representatives of the Archaea, Thermococcus sp. SN531 (Slobodkin et al., 2001), Geoglobus ahangari (Kashefi et al., 2002) and 'Candidatus Aciduliprofundum boonei ' (Reysenbach et al., 2006). In this paper, we report the isolation and characterization of a novel hyperthermophilic Fe(III)-reducing archaeon from the deepest of the known World Ocean hydrothermal fields.Strain SBH6 T was isolated from a fragment of a hydrothermal chimney-like structure. The sample was collected in March 2007 during the Serpentine cruise at the Ashadze hydrothermal field (12 u 589 210 N 44 u 519 470 W) on the Mid-Atlantic Ridge at a depth of 4100 m. For sample collection, sterilized microbiological boxes filled with...

bGeoglobus acetivorans is a hyperthermophilic anaerobic euryarchaeon of the order Archaeoglobales isolated from deep-sea hydrothermal vents. A unique physiological feature of the members of the genus Geoglobus is their obligate dependence on Fe(III) reduction, which plays an important role in the geochemistry of hydrothermal systems. The features of this organism and its complete 1,860,815-bp genome sequence are described in this report. Genome analysis revealed pathways enabling oxidation of molecular hydrogen, proteinaceous substrates, fatty acids, aromatic compounds, n-alkanes, and organic acids, including acetate, through anaerobic respiration linked to Fe(III) reduction. Consistent with the inability of G. acetivorans to grow on carbohydrates, the modified Embden-Meyerhof pathway encoded by the genome is incomplete. Autotrophic CO 2 fixation is enabled by the Wood-Ljungdahl pathway. Reduction of insoluble poorly crystalline Fe(III) oxide depends on the transfer of electrons from the quinone pool to multiheme c-type cytochromes exposed on the cell surface. Direct contact of the cells and Fe(III) oxide particles could be facilitated by pilus-like appendages. Genome analysis indicated the presence of metabolic pathways for anaerobic degradation of aromatic compounds and n-alkanes, although an ability of G. acetivorans to grow on these substrates was not observed in laboratory experiments. Overall, our results suggest that Geoglobus species could play an important role in microbial communities of deep-sea hydrothermal vents as lithoautotrophic producers. An additional role as decomposers would close the biogeochemical cycle of carbon through complete mineralization of various organic compounds via Fe(III) respiration. G eoglobus acetivorans SBH6T is a hyperthermophilic anaerobic euryarchaeon isolated from one of the world's deepest deepsea hydrothermal vents (Ashadze field; depth, 4,100 m) located on the Mid-Atlantic Ridge (1). A unique physiological feature of the members of the genus Geoglobus, which so far comprises only two species-G. ahangari and G. acetivorans-is their obligate dependence on Fe(III) reduction (1, 2). These microorganisms grow exclusively by coupling the oxidation of molecular hydrogen or organic compounds to the reduction of insoluble poorly crystalline Fe(III) oxide (ferrihydrite) or Fe(III) citrate. G. acetivorans can grow lithoautotrophically using CO 2 as a carbon source. G. acetivorans cannot use other electron acceptors such as sulfate, thiosulfate, elemental sulfur, nitrite, or oxygen for growth, and it is also unable to ferment organic compounds. Thus, these physiological features make G. acetivorans the ideal candidate for studies of the genomic and biochemical aspects of iron reduction.Microbial reduction of ferric iron plays an important role in the biogeochemical cycles of carbon, oxygen, and sulfur in the biosphere and has a considerable impact on the ecological situation in the modern environments (3). A more significant role may have been played by the reduction of iron in ...