A new thermophilic, xylanolytic, strictly anaerobic, rod-shaped bacterium, strain SEBR 7054T, was isolated from an African oil-producing well. Based on the presence of an outer sheath (toga) and 16s rRNA sequence analysis data, this organism was identified as a member of the genus Thermotoga. Strain SEBR 7054T possessed lateral flagella, had a G+C content of 50 mol%, produced traces of ethanol ffom glucose but no lactate, and grew optimally in the presence of 0 to 0.2% NaCl at 70°C. Its phenotypic and phylogenetic characteristics clearly differed from those reported for the five previously validly described Thermotoga species. Therefore, we propose that strain SEBR 7054T is a member of a new species of the genus Thermotoga, Thermotoga hypogea sp. nov. The type strain of T. hypogea is SEBR 7054 (= DSM 11164).Members of the order Thermotogales are rod-shaped bacteria that have a characteristic outer sheathlike structure called a toga. This order includes the following five genera: Thermotoga (18,22, 23,34,44), Thermosipho (19, 37), Fewidobacterium (1, 20, 32), Geotoga, and Petrotogu (9). It represents, along with the AquiJicales, the deepest phylogenetic branch in the domain Bacteria (45). The genus Thermotoga includes all of the hyperthermophiles (optimum temperature for growth, around 80°C) of the order Thermotogales (18, 21, 22) and the thermophiles (optimum temperature for growth, 65 to 70°C) recently isolated from oil fields (23,34). Stetter et al. (39) provided evidence of the presence of Thermotoga strains in oil fields. The isolation of Thennotoga elfii and Thermotoga subterranea from such ecosystems was reported soon thereafter (23,34). In contrast to Thermotoga maritima and i%ermotoga neapolitana, T. elfii and T. subterranea were not able to grow at temperatures above 75°C and reduced thiosulfate but not sulfur, which led to speculation that thiosulfate rather than sulfur may be an important electron acceptor in oil field ecosystems (34). The presence of thiosulfate is also thought to increase biocorrosion of oil field installations (8,27). We therefore initiated intensive studies to isolate Thermotoga strains from oil field subsurface ecosystems that grow at temperatures above 80°C and use thiosulfate as an electron acceptor. Our studies have focused on xylanolytic extremophilic microorganisms since thermostable xylanases have a potential use in paper primary-pulp manufacturing (33). In this paper, we describe the first isolation from oil field water of a xylanolytic Thermotoga species able to grow at temperatures up to 90°C. The phenotypic and phylogenetic characteristics of the new strain are consistent with its placement in a new species of the genus Thermotoga, Thermotoga hypogea sp. nov. MATERIALS AND METHODSSample collection and sample source. Strain SEBR 7054= was isolated from an oil-producing well in Cameroon in central Africa. The in situ temperature was 66"C, and the concentration of sodium chloride was 12 glliter. A 1-liter sample was collected at the wellhead as described elsewhere (3), t...

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A strictly anaerobic thiosulfate-reducing bacterium was isolated from a corroding offshore oil well in Congo and was designated strain SEBR 4207T. Pure culture of the strain induced a very active pitting corrosion of mild steel, with penetration rates of up to 4 mm per year. This constitutes the first experimental evidence of the involvement of thiosulfate reduction in microbial corrosion of steel. Strain SEBR 4207T cells were vibrios (3 to 5 by 1 pm), stained gram negative, and possessed lateral flagella. Spores were not detected. Optimum growth occurred in the presence of 3% NaCl at pH 7.0 and 42°C. Strain SEBR 4207T utilized peptides and amino acids, but not sugars or fatty acids. It fermented serine, histidine, and Casamino Acids, whereas arginine, glutamate, leucine, isoleucine, alanine, valine, methionine, and asparagine were only used in the presence of thiosulfate. Peptides were fermented to acetate, isobutyrate, isovalerate, 2-methylbutyrate, H,, and CO,. The addition of either thiosulfate or sulfur but not sulfate increased peptide utilization, growth rate, and biomass; during growth, H,S was produced and a concomitant decrease in H, was observed. The addition of either thiosulfate or sulfur also reversed H, inhibition. 16s rRNA sequence analysis indicates that strain SEBR 4207T is distantly related to members of the genus Thermoanuerobacter (83% similarity). Because the phenotypic and phylogenetic characteristics cannot be assigned to any described genus, strain SEBR 4207T is designated as a new species of a new genus, Dethiosulfovibrio peptidovorans gen. nov., sp. nov. Strain SEBR 4207T has been deposited in the Deutsche Sammlung von Mikroorganismen und zellkulturen GmbH (= DSM 11002).In 1989, Elf Congo experienced corrosion of the first 5 km of a 23-km main subsea pipeline that transported sour oil (i.e., H,S-containing petroleum) produced from the Emeraude oil field. The corroded segment was replaced, but it corroded again a year later. The whole line was then replaced and operated under a specifically designed biocide treatment regimen. The preliminary examination of the corroded iron showed that the breakthrough was due to bacterial pitting corrosion, with an unusually high penetration rate of about 1 cm per year. Chemical analysis of the pipeline water revealed the presence of up to 0.5 mM thiosulfate. It is likely that the thiosulfate was produced as a result of oxidation of the H,S naturally present in the oil field ecosystem by oxygen that is introduced in the pipelines during processing (10, 15, 22). The corrosion of pipelines was suspected to be due not only to sulfate but also to thiosulfate reduction by sulfate-reducing bacteria (SRB), because computer modeling had shown that thiosulfate reduction could induce the pitting corrosion of steel at higher rates than sulfate reduction (13).Since the pipeline was under a biocide treatment regimen during our microbiological investigations, the production fluids from several wellheads upstream of the line were collected and analyzed. Besides diffe...

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Aminomonas paucivorans gen. nov., sp. nov., a mesophil ic, anaerobic, amino-acid-uti I izing bacterium S. Baena,'g2 M.-L. Fardeau,l B. Ollivier,' M. Labat,' P. T h o r n a~,~ J.-L. Garcia' and B. K. C A novel, asaccharolytic, amino-acid-degrading bacterium, designated strain GLU-3l, was isolated from an anaerobic lagoon of a dairy wastewater treatment plant. Strain GLU-3l stained Gram-negative and was an obligately anaerobic, non-spore-forming, slightly curved, rod-shaped bacterium (0.3 x 400-6-0 pm) which existed singly or in pairs. The DNA G+C content was 43 mol%. Optimum growth occurred at 35 "C and pH 7.5 on arginine with a generation time of 16 h. Good growth was obtained on arginine, histidine, threonine and glycine. Acetate was the end-product formed from all these substrates, but in addition, a trace of formate was detected from arginine and histidine, and ornithine was produced from arginine. Strain GLU-3T grew slowly on glutamate and produced acetate, carbon dioxide, formate, hydrogen and traces of propionate as the end-products. In syntrophic association with Methanobacterium formiciafm, strain GLU-3T oxidized arginine, histidine and glutamate to give propionate as the major product; acetate, carbon dioxide and methane were also produced. Strain GLU-3T did not degrade alanine and the branched-chain amino acids valine, leucine and isoleucine either in pure culture or in association with M. formicicum. The nearest phylogenetic relative of strain GLU-3l was the thermophile Selenomonas acidaminovorans (similarity value of 895 %). As strain GLU-3l is phylogenetically, physiologically and genotypically different from other amino-acid-degrading genera, it is proposed that it should be designated a new species of a new genus Aminomonas paucivorans gen. nov., sp. nov. (DSM 122603.