H2oxidation in the presence of thiosulfate, by aThermoanaerobacterstrain isolated from an oil-producing well

Assessing Microbial Corrosion Risk on Offshore Crude Oil Production Topsides under Conditions of Nitrate and Nitrite Treatment for Souring

Oilfield souring is a detrimental effect caused by sulfate-reducing microorganisms that reduce sulfate to sulfide during their respiration process. Nitrate or nitrite can be used to mitigate souring, but may also impart a corrosion risk. Produced fluids sampled from the topside infrastructure of two floating, production, storage, and offloading (FPSO) vessels (Platform A and Platform B) were assessed for microbial corrosion under nitrate and nitrite breakthrough conditions using microcosm tests incubated at 54 °C. Microbial community compositions on each individual FPSO were similar, while those between the two FPSO vessels differed. Platform B microbial communities responded as expected to nitrate breakthrough conditions, where nitrate-reducing activity was enhanced and sulfate reduction was inhibited. In contrast, nitrate treatments of Platform A microbial communities were not as effective in preventing sulfide production. Nitrite breakthrough conditions had the strongest sulfate reduction inhibition in samples from both platforms, but exhibited the highest pitting density. Live experimental replicates with no nitrate or nitrite additive yielded the highest general corrosion rates in the study (up to 0.48 mm/year), while nitrate- or nitrite-treated fluids revealed general corrosion rates that are considered low or moderate (<0.12 mm/year). Overall, the results of this study provide a description of nitrogen- and sulfur-based microbial activities under thermophilic conditions, and their risk for MIC that can occur along fluid processing lines on FPSO topsides that process fluids during offshore oil production operations.

Fusibacter fontis sp. nov., a sulfur-reducing, anaerobic bacterium isolated from a mesothermic Tunisian spring

Strain KhalAKB1T, a mesophilic, anaerobic, rod-shaped bacterium, was isolated from water collected from a mesothermic Tunisian spring. Cells were Gram-staining-positive rods, occurring singly or in pairs and motile by one lateral flagellum. Strain KhalAKB1T grew at 15–45 °C (optimum 30 °C), at pH 5.5–8.5 (optimum pH 7.0) and in the presence of 0–35 g NaCl l− 1 (optimum 1 g NaCl l− 1). It fermented yeast extract and a wide range of carbohydrates including cellobiose, d-glucose, d-ribose, sucrose, d-xylose, maltose, d-galactose and starch as electron donors. Acetate, ethanol, CO2 and H2 were end products of glucose metabolism. It reduced elemental sulfur, but not sulfate, thiosulfate or sulfite, into sulfide. The DNA G+C content was 37.6 mol%. The predominant cellular fatty acids were C14 : 0 and C16 : 0. Phylogenetic analysis of the 16S rRNA gene sequence suggested Fusibacter bizertensis as the closest relative of this isolate (identity of 97.2 % to the type strain). Based on phenotypic, phylogenetic and genotypic taxonomic characteristics, strain KhalAKB1T is proposed to be assigned to a novel species within the genus Fusibacter, order Clostridiales, Fusibacter fontis sp. nov. The type strain is KhalAKB1T ( = DSM 28450T = JCM 19912T).

Fusibacter bizertensis sp. nov., isolated from a corroded kerosene storage tank

Strain LTF Kr01T, a novel mesophilic, anaerobic, halotolerant, rod-shaped bacterium, was isolated from a drain at the bottom of a corroded kerosene storage tank of the Société Tunisienne des Industries de Raffinage (STIR), Bizerte, northern Tunisia. Cells were Gram-positive-staining rods, occurred singly or in pairs, and were motile by one lateral flagellum. Strain LTF Kr01T grew at temperatures between 15 and 40 °C (optimum 30 °C), between pH 5.5 and 8.2 (optimum pH 7.2) and at NaCl concentrations between 0 and 50 g l−1 (optimum 5 g l−1). It reduced thiosulfate and elemental sulfur into sulfide, but did not reduce sulfate or sulfite. It utilized a wide range of carbohydrates (cellobiose, d-glucose, d-fructose, d-mannitol, d-ribose, sucrose, d-xylose, maltose, d-galactose, starch and trehalose) and produced acetate, CO2 and H2 as end products from glucose fermentation. The DNA G+C content was 37.4 mol%. The predominant cellular fatty acids were C14 : 0 and C16 : 0. Phylogenetic analysis of the 16S rRNA gene sequence suggested that Fusibacter tunisiensis was the closest relative of strain LTF Kr01T (gene sequence similarity of 94.6 %). Based on phenotypic, phylogenetic and genotypic taxonomic characteristics, strain LTF Kr01T is proposed to represent a novel species of the genus Fusibacter , order Clostridiales , for which the name Fusibacter bizertensis sp. nov. is proposed. The type strain is LTF Kr01T ( = DSM 28034T = JCM 19376T).

Caldilinea tarbellica sp. nov., a filamentous, thermophilic, anaerobic bacterium isolated from a deep hot aquifer in the Aquitaine Basin

An anaerobic, thermophilic, filamentous (0.45 × >100 µm) bacterium, designated D1-25-10-4T, was isolated from a deep hot aquifer in France. Cells were non-motile and Gram-negative. Growth was observed at 43–65 °C (optimum 55 °C), at pH 6.8–7.8 (optimum pH 7.0) and with 0–5 g NaCl l−1 (optimum 0 g NaCl l−1). Strain D1-25-10-4T was a chemo-organotroph and fermented ribose, maltose, glucose, galactose, arabinose, fructose, mannose, sucrose, raffinose, xylose, glycerol, fumarate, peptone, starch and xylan. Yeast extract was required for growth. Sulfate, thiosulfate, sulfite, elemental sulfur, nitrate, nitrite and fumarate were not used as terminal electron acceptors. The G+C content of the DNA was 61.9 mol%. The major cellular fatty acids of strain D1-25-10-4T were C17 : 0, C18 : 0, C16 : 0 and iso-C17 : 0. The closest phylogenetic relative of strain D1-25-10-4T was Caldilinea aerophila STL-6-O1T (97.9 % 16S rRNA gene sequence similarity). DNA–DNA relatedness between strain D1-25-10-4T and Caldilinea aerophila DSM 14535T was 8.7±1 %. On the basis of phylogenetic, genotypic and phenotypic characteristics, strain D1-25-10-4T represents a novel species within the genus Caldilinea, class Caldilineae, phylum Chloroflexi, for which the name Caldilinea tarbellica sp. nov. is proposed. The type strain is D1-25-10-4T ( = DSM 22659T  = JCM 16120T).

Characterization of Halanaerobaculum tunisiense gen. nov., sp. nov., a new halophilic fermentative, strictly anaerobic bacterium isolated from a hypersaline lake in Tunisia

A new halophilic anaerobe was isolated from the hypersaline surface sediments of El-Djerid Chott, Tunisia. The isolate, designated as strain 6SANG, grew at NaCl concentrations ranging from 14 to 30%, with an optimum at 20-22%. Strain 6SANG was a non-spore-forming, non-motile, rod-shaped bacterium, appearing singly, in pairs, or occasionally as long chains (0.7-1 x 4-13 microm) and showed a Gram-negative-like cell wall pattern. It grew optimally at pH values between 7.2 and 7.4, but had a very broad pH range for growth (5.9-8.4). Optimum temperature for growth was 42 degrees C (range 30-50 degrees C). Strain 6SANG required yeast extract for growth on sugars. Glucose, sucrose, galactose, mannose, maltose, cellobiose, pyruvate, and starch were fermented. The end products from glucose fermentation were acetate, butyrate, lactate, H(2), and CO(2). The G + C ratio of the DNA was 34.3 mol%. Strain 6SANG exhibited 16S rRNA gene sequence similarity values of 91-92% with members of the genus Halobacteroides, H. halobius being its closest phylogenetic relative. Based on phenotypic and phylogenetic characteristics, we propose that this bacterium be classified as a novel species of a novel genus, Halanaerobaculum tunisiense gen. nov., sp. nov. The type strain is 6SANG(T) (=DSM 19997(T)=JCM 15060(T)).

Exiguobacterium profundum sp. nov., a moderately thermophilic, lactic acid-producing bacterium isolated from a deep-sea hydrothermal vent

A facultatively anaerobic, halotolerant, moderately thermophilic and non-sporulating bacterium, designated strain 10C(T), was isolated from deep-sea hydrothermal vent samples collected on the 13 degrees N East Pacific Rise at a depth of approximately 2600 m. Cells of strain 10C(T) were Gram-positive, motile rods, and grew optimally at 45 degrees C (range 12-49 degrees C), pH 7.0 (range pH 5.5-9.5) and 0-2 % NaCl (range 0-11 %). (+)-L-Lactate was the main organic acid detected from carbohydrate fermentation with traces of formate, acetate and ethanol. Strain 10C(T) was catalase-positive, oxidase-negative and reduced nitrate to nitrite under anaerobic conditions. The DNA G+C content was 50.4 mol%. Its closest phylogenetic relatives were Exiguobacterium aestuarii TF-16(T) and Exiguobacterium marinum TF-80(T) (16S rRNA gene sequence similarity >99 %). However, strain 10C(T) differed genotypically from these two Exiguobacterium species as indicated by DNA-DNA relatedness data. Therefore, on the basis of phenotypic, genotypic and phylogenetic characteristics, strain 10C(T) is considered to represent a novel species of the genus Exiguobacterium, for which the name Exiguobacterium profundum sp. nov. is proposed. The type strain is 10C(T) (=CCUG 50949(T)=DSM 17289(T)).

Clostridium tunisiense sp. nov., a new proteolytic, sulfur-reducing bacterium isolated from an olive mill wastewater contaminated by phosphogypse

A new sporulated fermentative bacterium designated strain E1(T) (T=type strain), was isolated from an anaerobic mud of an olive mill wastewater basin contaminated by phosphogypse produced by a Tunisian factory. Strain E1(T) was a motile Gram-positive slightly curved rod with spherical terminal spore swelling the cell. It grew between 18 degrees C and 43 degrees C with an optimum at 37 degrees C and pH 7.8 (range 5.5-8.7), without NaCl (range 0-3%). Strain E1(T) was a chemoorganotrophic anaerobic bacterium fermenting only proteins and amino acids. Yeast extract was required for growth. Elemental sulfur was used as terminal electron acceptor. The G+C content of the DNA was 32.6 mol%. The closest phylogenetical relatives of strain E1(T) were Clostridium thiosulfatireducens and C. subterminale (97.3% similarity for partial rRNA gene sequences). DNA-DNA hybridization values between strain E1(T) and both species were 17% and 20.8%, respectively. On the basis of differences in genotypic and phenotypic characteristics, strain E1(T) (DSM 15206(T), CIP 107666(T)) is proposed as the type strain of a new species, C. tunisiense sp. nov. GenBank accession number for the 16S rRNA gene sequence of strain E1(T) is AY187622.

Identification and Phylogenetic analysis of thermophilic sulfate-reducing bacteria in oil field samples by 16S rDNA gene cloning and sequencing

Thermophilic sulfate-reducing bacteria (SRB) have been recognized as an important source of hydrogen sulfide (H2S) in hydrocarbon reservoirs and in production systems. Four thermophilic SRB enrichment cultures from three different oil field samples (sandstone core, drilling mud, and production water) were investigated using 16S rDNA sequence comparative analysis. In total, 15 different clones were identified. We found spore-forming, low G+C content, thermophilic, sulfate-reducing Desulfotomaculum-related sequences present in all oil field samples, and additionally a clone originating from sandstone core which was assigned to the mesophilic Desulfomicrobium group. Furthermore, three clones related to Gram-positive, non-sulfate-reducing Thermoanaerobacter species and four clones close to Clostridium thermocopriae were found in enrichment cultures from sandstone core and from production water, respectively. In addition, the deeply rooted lineage of two of the clones suggested previously undescribed, Gram-positive, low G+C content, thermophilic, obligately anaerobic bacteria present in production water. Such thermophilic, non-sulfate-reducing microorganisms may play an important ecological role alongside SRB in oil field environments.

Isolation of sulfate-reducing bacteria from Tunisian marine sediments and description of Desulfovibrio bizertensis sp. nov

Several strains of sulfate-reducing bacteria were isolated from marine sediments recovered near Tunis, Korbous and Bizerte, Tunisia. They all showed characteristics consistent with members of the genus Desulfovibrio. One of these strains, designated MB3T, was characterized further. Cells of strain MB3T were slender, curved, vibrio-shaped, motile, Gram-negative, non-spore-forming rods. They were positive for desulfoviridin as bisulfite reductase. Strain MB3T grew at temperatures of 15–45 °C (optimum 40 °C) and at pH 6.0–8.1 (optimum pH 7.0). NaCl was required for growth (optimum 20 g NaCl l−1). Strain MB3T utilized H2 in the presence of acetate with sulfate as electron acceptor. It also utilized lactate, ethanol, pyruvate, malate, fumarate, succinate, butanol and propanol as electron donors. Lactate was oxidized incompletely to acetate. Strain MB3T fermented pyruvate and fumarate (poorly). Electron acceptors utilized included sulfate, sulfite, thiosulfate, elemental sulfur and fumarate, but not nitrate or nitrite. The G+C content of the genomic DNA was 51 mol%. On the basis of genotypic, phenotypic and phylogenetic characteristics, strain MB3T (=DSM 18034T=NCIMB 14199T) is proposed as the type strain of a novel species, Desulfovibrio bizertensis sp. nov.

Thermosipho atlanticus sp. nov., a novel member of the Thermotogales isolated from a Mid-Atlantic Ridge hydrothermal vent

A novel anaerobic, thermophilic and heterotrophic bacterium, designated strain DV1140T, was isolated from a deep-sea hydrothermal vent sample from the Mid-Atlantic Ridge. The cells were non-motile straight rods, 1·8 μm long and 0·4 μm wide, surrounded by an outer sheath-like structure (toga). They grew at 45–80 °C (optimum 65 °C), pH 5·0–9·0 (optimum pH 6·0) and at sea salt concentrations of 20–60 g l−1(optimum 30 g l−1). Strain DV1140Twas able to ferment yeast extract, peptone, brain heart infusion, gelatin, starch, galactose, arabinose, glucose, trehalose and cellobiose. The fermentation products identified on glucose in the presence of yeast extract and peptone were acetate, isovalerate and hydrogen. The G+C content of the genomic DNA was 33 mol%. Phylogenetic analysis of the 16S rRNA gene sequence (GenBank accession number AJ577471) located the strain within the genusThermosiphoin the bacterial domain. On the basis of 16S rRNA gene sequence comparisons, and physiological and biochemical characteristics, the isolate represents a novel species, for which the nameThermosipho atlanticussp. nov. is proposed. The type strain is DV1140T(=CIP 108053T=DSM 15807T).

Isolation from oil reservoirs of novel thermophilic anaerobes phylogenetically related to Thermoanaerobacter subterraneus: reassignment of T. subterraneus, Thermoanaerobacter yonseiensis, Thermoanaerobacter tengcongensis and Carboxydibrachium pacificum to Caldanaerobacter subterraneus gen. nov., sp. nov., comb. nov. as four novel subspecies

Novel thermophilic, anaerobic, Gram-positive, rod-shaped bacteria, strains SL9 and OCA1, were isolated from oilfields in France and Australia, respectively. Both strains, together with Thermoanaerobacter yonseiensis KB-1(T) (=DSM 13777(T)), Thermoanaerobacter tengcongensis MB4(T) (=DSM 15242(T)) and Carboxydibrachium pacificum JM(T) (=DSM 12653(T)), possessed genomic (DNA-DNA hybridization studies) and phylogenetic similarities with Thermoanaerobacter subterraneus SEBR 7858(T) (=DSM 13054(T)), which was isolated recently from an oilfield reservoir in south-west France. Marked phenotypic differences exist between the three oilfield isolates (T. subterraneus, strain OCA1 and strain SL9): they include temperature range for growth and substrates used. Differences were also observed in the DNA G+C contents of all organisms. Similarly to T. subterraneus, strains SL9 and OCA1, and also T. yonseiensis, T. tengcongensis and Carboxydibrachium pacificum, produced acetate and L-alanine as major end products of glucose metabolism [0.8-1.0 mol L-alanine produced (mol glucose consumed)(-1)] and reduced thiosulfate, but not sulfate, to sulfide. Because of these significant metabolic and phylogenetic differences between the oilfield isolates (T. subterraneus, strain OCA1 and strain SL9), T. yonseiensis, T. tengcongensis and Carboxydibrachium pacificum and other Thermoanaerobacter species, it is proposed to reassign them as a novel genus and species, Caldanaerobacter subterraneus gen. nov., sp. nov., comb. nov., with the creation of four novel subspecies, Caldanaerobacter subterraneus subsp. subterraneus subsp. nov., comb. nov., Caldanaerobacter subterraneus subsp. yonseiensis subsp. nov., comb. nov., Caldanaerobacter subterraneus subsp. tengcongensis subsp. nov., comb. nov. and Caldanaerobacter subterraneus subsp. pacificus subsp. nov., comb. nov.

Petrobacter succinatimandens gen. nov., sp. nov., a moderately thermophilic, nitrate-reducing bacterium isolated from an Australian oil well

A novel Gram-negative, aerobic and moderately thermophilic bacterium, strain 4BONT, was isolated from a non-water-flooded Australian terrestrial oil reservoir. Cells were non-spore-forming straight rods, which were motile by means of a polar flagellum. The optimum growth conditions were 55 °C, pH 6·9 and 0·5 % NaCl. Strain 4BONT was oxidase- and catalase-positive; it grew on fumarate, pyruvate, succinate, formate, ethanol and yeast extract in the presence of oxygen or nitrate as terminal electron acceptor. Nitrate was reduced to nitrous oxide. The DNA G+C content of the strain was 58·6 mol%. The closest phylogenetic relative of strain 4BONT was Hydrogenophilus thermoluteolus (similarity of 91·8 %), of the β-Proteobacteria. As strain 4BONT is physiologically and phylogenetically different from H. thermoluteolus, it is proposed that it be assigned to a novel species of a novel genus, Petrobacter succinatimandens gen. nov., sp. nov. The type strain is 4BONT (=DSM 15512T=CIP 107790T).

Petrotoga mexicana sp. nov., a novel thermophilic, anaerobic and xylanolytic bacterium isolated from an oil-producing well in the Gulf of Mexico

A novel anaerobic, thermophilic, xylanolytic, motile rod-shaped bacterium with a sheath-like outer structure (toga) was isolated from a Mexican oil well in the Gulf of Mexico. Strain MET12T was a Gram-negative bacterium, reducing elemental sulfur, thiosulfate and sulfite to hydrogen sulfide. Its optimum growth conditions were 55 °C, pH 6·6, 3 % NaCl and 0·15 % MgCl2.6H2O. The DNA G+C content was 36·1 mol%. Phylogenetically, strain MET12T was related to members of genus Petrotoga, with similarities to Petrotoga mobilis, Petrotoga sibirica, Petrotoga miotherma and Petrotoga olearia varying from 97·6 to 98·8 %. However DNA–DNA relatedness values between these species and strain MET12T were lower than 70 %. As strain MET12T (=DSM 14811T=CIP 107371T) was genomically and phenotypically different from existing Petrotoga species, it is proposed as the type strain of a novel species, Petrotoga mexicana sp. nov.

Desulfonauticus submarinus gen. nov., sp. nov., a novel sulfate-reducing bacterium isolated from a deep-sea hydrothermal vent

A novel moderately thermophilic, hydrogenotrophic, sulfate-reducing bacterium, strain 6N(T) (=DSM 15269(T)=CIP 107713(T)), was isolated from matrixes of Alvinella and Riftia originating from deep-sea hydrothermal-vent samples collected on the 13 degrees N East-Pacific Rise at a depth of approximately 2600 m. It was a Gram-negative, non-sporulating, curved rod, motile with one polar flagellum, that did not possess desulfoviridin. It grew at temperatures ranging from 30 to 60 degrees C, with an optimum at 45 degrees C, in the presence of 0-5 % NaCl (optimum 2 %). Strain 6N(T) utilized only H(2)/CO(2) and formate as electron donors with acetate as carbon source. Sulfate, sulfite, thiosulfate and elemental sulfur were used as terminal electron acceptors during hydrogen oxidation. The G+C content of DNA was 34.4 mol%. Strain 6N(T) grouped with members of the family Desulfohalobiaceae in the delta-subclass of the PROTEOBACTERIA: Its closest phylogenetic relative was Desulfonatronovibrio hydrogenovorans, with only 90 % similarity between the sequences of the genes encoding 16S rRNA. Because of significant phylogenetic differences from all sulfate-reducing bacteria described so far in the domain Bacteria, this novel thermophile is proposed to be assigned to a new genus and species, Desulfonauticus submarinus gen. nov., sp. nov.

Clostridium caminithermale sp. nov., a slightly halophilic and moderately thermophilic bacterium isolated from an Atlantic deep-sea hydrothermal chimney

A strictly anaerobic, slightly halophilic and moderately thermophilic, sporulating rod designated strain DVird3T was isolated from deep-sea hydrothermal vent samples collected at a depth of approximately 800 m on the Atlantic Ocean Ridge. Strain DVird3T possessed a few laterally inserted flagella, had a DNA G + C content of 33.1 mol% and grew optimally at pH 6.6 and at 45 degrees C. Growth was observed at temperatures between 20 and 58 degrees C and at pH values between 5.8 and 8.2. The optimum NaCl concentration for growth was 3% sea salt (30 g l(-1)); no growth was observed in the presence of 15 or 60 g sea salt l(-1). Strain DVird3T is heterotrophic and utilizes some sugars and various single amino acids. Acetate was the main fatty acid detected from carbohydrate fermentation, together with H2 and CO2. Gelatin was used as an energy source. It performed the Stickland reaction. Phylogenetically, strain DVird3T branched with members of cluster XI of the order Clostridiales, with Clostridium halophilum as its closest relative (similarity of 94.6%). On the basis of its phenotypic, genotypic and phylogenetic characteristics, strain DVird3T (= DSM 15212T = CIP 107654T) is proposed as the type strain of a novel species of the genus Clostridium, Clostridium caminithermale sp. nov.

Desulfovibrio hydrothermalis sp. nov., a novel sulfate-reducing bacterium isolated from hydrothermal vents

Mesophilic, hydrogenotrophic, sulfate-reducing bacteria were isolated from a deep-sea hydrothermal chimney sample collected at 13 degrees N on the East-Pacific Rise at a depth of 2,600 m. Two strains (BL5 and H9) were found to be phylogenetically similar to Desulfovibrio profundus (similarity >99%), whereas two other strains (H1 and AM13T) were found to be phylogenetically distinct (similarity 96.4%) from Desulfovibrio zosterae, their closest relative. Strain AM13T was characterized further. It was a barophilic, Gram-negative, non-sporulating, motile, vibrio-shaped or sigmoid bacterium possessing desulfoviridin. It grew at temperatures ranging from 20 to 40 degrees C, with an optimum at 35 degrees C in the presence of 2.5% NaCl. The pH range for growth was 6.7-8.2 with an optimum around 7.8. Strain AM13T utilized H2/CO2, lactate, formate, ethanol, choline and glycerol as electron donors. Electron acceptors were sulfate, sulfite and thiosulfate, but not elemental sulfur or nitrate. The G + C content of DNA was 47 mol%. Strain AM13T (= DSM 14728T = CIP107303T) differed from D. zosterae not only phylogenetically, but also genomically (DNA-DNA reassociation value between the two bacteria was 23.8%) and phenotypically. This isolate is therefore proposed as the type strain of a novel species of the genus Desulfovibrio, Desulfovibrio hydrothermalis sp. nov.

Construction and physiological studies of hydrogenase depleted mutants of Desulfovibrio fructosovorans

Desulfovibrio fructosovorans possesses two periplasmic hydrogenases (a nickel-iron and an iron hydrogenase) and a cytoplasmic NADP-dependent hydrogenase. The hydAB genes encoding the periplasmic iron hydrogenase were replaced, in the wild-type strain as well as in single mutants depleted of one of the other two hydrogenases, by the acc1 gene encoding resistance to gentamycin. Molecular characterization and remaining activity measurements of the resulting single and double mutants were performed. All mutated strains exhibited similar growth when H(2) was the electron donor but they grew differently on fructose, lactate or pyruvate as electron donors. Our results indicate that the loss of one enzyme might be compensated by another even though hydrogenases have different localization in the cells.

Culture-dependent and culture-independent characterization of microbial assemblages associated with high-temperature petroleum reservoirs

Recent investigations of oil reservoirs in a variety of locales have indicated that these habitats may harbor active thermophilic prokaryotic assemblages. In this study, we used both molecular and culture-based methods to characterize prokaryotic consortia associated with high-temperature, sulfur-rich oil reservoirs in California. Enrichment cultures designed for anaerobic thermophiles, both autotrophic and heterotrophic, were successful at temperatures ranging from 60 to 90 degrees C. Heterotrophic enrichments from all sites yielded sheathed rods (Thermotogales), pleomorphic rods resembling Thermoanaerobacter, and Thermococcus-like isolates. The predominant autotrophic microorganisms recovered from inorganic enrichments using H(2), acetate, and CO(2) as energy and carbon sources were methanogens, including isolates closely related to Methanobacterium, Methanococcus, and Methanoculleus species. Two 16S rRNA gene (rDNA) libraries were generated from total community DNA collected from production wellheads, using either archaeal or universal oligonucleotide primer sets. Sequence analysis of the universal library indicated that a large percentage of clones were highly similar to known bacterial and archaeal isolates recovered from similar habitats. Represented genera in rDNA clone libraries included Thermoanaerobacter, Thermococcus, Desulfothiovibrio, Aminobacterium, Acidaminococcus, Pseudomonas, Halomonas, Acinetobacter, Sphingomonas, Methylobacterium, and Desulfomicrobium. The archaeal library was dominated by methanogen-like rDNAs, with a lower percentage of clones belonging to the Thermococcales. Our results strongly support the hypothesis that sulfur-utilizing and methane-producing thermophilic microorganisms have a widespread distribution in oil reservoirs and the potential to actively participate in the biogeochemical transformation of carbon, hydrogen, and sulfur in situ.

Desulfovibrio aminophilus sp. nov., a novel amino acid degrading and sulfate reducing bacterium from an anaerobic dairy wastewater lagoon

A mesophilic strain of sulfate-reducing bacterium, designated ALA-3T (T = type strain), was isolated from an anaerobic lagoon of a dairy wastewater treatment plant. The curved, Gram-negative, non-sporeforming cells (0.2 x 3.0-4.0 microns) existed singly or in chains, and were motile by single polar flagella. Optimum growth occurred at 35 degrees C and pH 7.5 on a medium containing lactate and sulfate. Thiosulfate or sulfite but not elemental sulfur, nitrate, or fumarate could also replace sulfate as an electron acceptor. Formate, alanine, aspartate, leucine, isoleucine, valine, and methionine, H2/CO2 and ethanol also served as electron donors with sulfate as an electron acceptor. Pyruvate, casamino acids, peptone, serine, glycine, cysteine and threonine were fermented. Sulfite and thiosulfate were disproportionated to sulfate and sulfide. The G + C content of the DNA was 66 mol % G + C. Phylogenetic analysis revealed that Desulfovibrio africanus was the nearest relative (similarity of 89%). Strain ALA-3T is physiologically and phylogenetically different from other Desulfovibrio species, and is designated Desulfovibrio aminophilus sp. nov. (DSM 12254).

Aminobacterium colombiensegen. nov. sp. nov., an Amino Acid-degrading Anaerobe Isolated from Anaerobic Sludge

A new gram-negative, non-sporulating, mesophilic, amino acid fermenting bacterium, designated strain ALA-1(T) (T = type strain), was isolated from an anaerobic lagoon of a dairy wastewater treatment plant. The strain is curved (3-4 microm x 0.2-0.3 microm) and occurs singly or in pairs. Optimum growth occurs at 37 degrees C and pH 7.3. The G+C content of the DNA is 46 mol %. The strain requires yeast extract for growth, grows poorly on casamino acids, peptones, cysteine, and alpha-ketoglutarate, but readily grows on serine, threonine, glycine and pyruvate. When cocultured with the hydrogenotrophic methanogen Methanobacterium formicicum, strain ALA-1(T) oxidized alanine, glutamate, leucine, isoleucine, valine, aspartate, and methionine. Phylogenetic analysis revealed that it forms a distinct and independent line of descent in the vicinity of Dethiosulfovibrio peptidovorans, Dictyoglomus thermophilum, and Anaerobaculum thermoterrenum which are members of the low G+C containing gram-positive bacteria. The phylogenetic results concur with the phenotypic and genomic data which reveal that it is a novel strain. Based on these findings, we designate strain ALA-1(T) as Aminobacterium colombiense (DSM 12261) gen. nov., sp. nov.

Utilization of Serine, Leucine, Isoleucine, and Valine byThermoanaerobacter brockiiin the Presence of Thiosulfate orMethanobacteriumsp. as Electron Acceptors

Thermoanaerobacter brockii fermented serine to acetate and ethanol. It oxidized leucine to isovalerate, isoleucine to 2-methylbutyrate, and valine to isobutyrate only in the presence of thiosulfate, or when co-cultured with Methanobacterium sp. This oxidative deamination was rendered thermodynamically possible by the ability ofT. brockii to reduce thiosulfate to sulfide or the transfer of reducing equivalents to the hydrogenotrophic methanogen. The results suggest that T. brockii may be of ecological significance in thermal environments in the turnover of amino acids, especially with thiosulfate or H(2)-utilizing methanogens are present.

Effect of thiosulphate as electron acceptor on glucose and xylose oxidation by Thermoanaerobacter finnii and a Thermoanaerobacter sp. isolated from oil field water

During glucose and xylose fermentation, Thermoanaerobacter finnii was observed to produce lactate, acetate, H2 and CO2, with ethanol being the major end product. Thermoanaerobacter strain SEBR 5268, an isolate from an oil field, also produced a similar range of end products from glucose and xylose fermentation, with the exception that both ethanol and lactate were the major products of sugar metabolism. Both these strains were able to reduce thiosulphate to sulphide in the presence of these two substrates, with acetate being the dominant metabolite in that case. In addition, a faster growth rate and increased cell yield were obtained in the presence of thiosulphate, than in its absence. The higher concentrations of acetate produced in the presence of thiosulphate rather than without any electron acceptor indicated that more ATP was generated from substrate-level phosphorylation. These results have implications for our understanding of the breakdown of carbohydrates present in organic matter found in the natural ecological niches of Thermoanaerobacter species (sulphide-, elemental sulphur- or sulphate-rich thermal hot springs and oil fields).