Desulfotomaculum aquiferis sp. nov. and Desulfotomaculum profundi sp. nov., isolated from a deep natural gas storage aquifer.

Two novel strictly anaerobic bacteria, strains Bs105T and Bs107T, were isolated from a deep aquifer-derived hydrocarbonoclastic community. The cells were rod-shaped, not motile and had terminal spores. Phylogenetic affiliation and physiological properties revealed that these isolates belong to two novel species of the genus Desulfotomaculum. Optimal growth temperatures for strains Bs105T and Bs107T were 42 and 45 °C, respectively. The estimated G+C content of the genomic DNA was 42.9 and 48.7 mol%. For both strains, the major cellular fatty acid was palmitate (C16 : 0). Specific carbon fatty acid signatures of Gram-positive bacteria (iso-C17 : 0) and sulfate-reducing bacteria (C17 : 0cyc) were also detected. An insertion was revealed in one of the two 16S rRNA gene copies harboured by strain Bs107T. Similar insertions have previously been highlighted among moderately thermophilic species of the genus Desulfotomaculum. Both strains shared the ability to oxidize aromatic acids (Bs105T: hydroquinone, acetophenone, para-toluic acid, 2-phenylethanol, trans-cinnamic acid, 4-hydroxybenzaldehyde, benzyl alcohol, benzoic acid 4-hydroxybutyl ester; Bs107T: ortho-toluic acid, benzoic acid 4-hydroxybutyl ester). The names Desulfotomaculum aquiferis sp. nov. and Desulfotomaculum profundi sp. nov. are proposed for the type strains Bs105T (=DSM 24088T=JCM 31386T) and Bs107T (=DSM 24093T=JCM 31387T).

Desulfotomaculum ferrireducens sp. nov., a moderately thermophilic sulfate-reducing and dissimilatory Fe(III)-reducing bacterium isolated from compost.

A novel dissimilatory Fe(III)-reducing bacterium, designated strain GSS09T, was isolated from a compost sample by using a solid medium containing acetate and ferrihydrite as electron donor and electron acceptor, respectively. Cells of strain GSS09T were anaerobic, Gram-stain-positive, motile, endospore-forming and rod-shaped. Growth occurred at 30-55 °C (optimum 50 °C), at pH 6.5-9.0 (optimum pH 7.5) and in the presence of 0-3 % (w/v) NaCl (optimum 1 %). Both sulfur compounds such as sulfate, sulfite and thiosulfate and Fe(III) oxides such as ferrihydrite could be utilized as electron acceptors. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GSS09T was related closely to Desulfotomaculum hydrothermale Lam5T (94.5 % sequence similarity). The major fatty acids were C16 : 0 and C16 : 1ω7c/C16 : 1ω6c. The G+C content of the genomic DNA was 49.1 mol%. On the basis of phylogenetic analysis, phenotypic characterization and physiological tests, strain GSS09T is considered to represent a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum ferrireducens sp. nov. is proposed. The type strain is GSS09T (=KCTC 15523T=MCCC 1K01254T).

Desulfotomaculum tongense sp. nov., a moderately thermophilic sulfate-reducing bacterium isolated from a hydrothermal vent sediment collected from the Tofua Arc in the Tonga Trench.

A novel, strictly anaerobic, moderately thermophilic, endospore-forming, sulfate-reducing bacterium, designated TGB60-1T, was isolated from a hydrothermal sediment vent collected from the Tofua Arc in the Tonga Trench. The strain was characterized phenotypically and phylogenetically. The isolated strain was observed to be Gram-positive, with slightly curved rod-shaped cells and a polar flagellum. Strain TGB60-1T was found to grow anaerobically at 37­60 °C (optimum, 50 °C), at pH 6.0­8.5 (optimum, pH 7.0) and with 1.0­4.0 % (w/v) NaCl (optimum, 3.0 %). The electron acceptors utilised were determined to be sulfate, sulfite, and thiosulfate. Strain TGB60-1T was found to utilise pyruvate and H2 as electron donors. Strain TGB60-1T was determined to be related to representatives of the genus Desulfotomaculum and the closest relatives within this genus were identified as Desulfotomaculum halophilum SEBR 3139T, Desulfotomaculum alkaliphilum S1T and Desulfotomaculum peckii LINDBHT1T (92.7, 92.1, and 91.8 % 16S rRNA gene sequence similarity, respectively). The major fatty acids (>20 %) were identified as C16:0 and C18:1 ω7c. The G+C content of the genomic DNA of this novel bacterium was determined to be 53.9 mol%. Based on this polyphasic taxonomic study, strain TGB60-1T is considered to represent a novel species in the genus Desulfotomaculum, for which the name Desulfotomaculum tongense sp. nov. is proposed. The type strain of D. tongense is strain TGB60-1T (= KTCT 4534T = JCM 18733T).

Desulfotomaculum intricatum sp. nov., a sulfate reducer isolated from freshwater lake sediment.

A novel spore-forming, sulfate-reducing bacterium, strain SR45(T), was isolated from sediment of a freshwater lake, Lake Mizugaki, in Japan. Cells of strain SR45 were rod-shaped (1.0-1.5×2.0-5.0 µm) and weakly motile; Gram staining and the KOH lysis test were negative. For growth, the optimum pH was 6.4-6.8 and the optimum temperature was 42-45 °C. Strain SR45(T) used sulfate, thiosulfate, sulfite and elemental sulfur as electron acceptors but not Fe(III). The G+C content of the genomic DNA was 41.1 mol%. Phylogenetic analyses based on genes for the 16S rRNA and DNA gyrase (gyrB) revealed that the isolated strain belonged to the family Peptococcaceae in the class Clostridia. The closest relative is Desulfotomaculum acetoxidans 5575(T), with 16S rRNA gene sequence similarity of 92-94 %. It is suggested that the strain is the second isolated member of Desulfotomaculum subcluster Ie. The isolate had multiple 16S rRNA gene copies, with 13 different sequences. On the basis of phylogenetic and phenotypic characterization, the name Desulfotomaculum intricatum sp. nov. is proposed, with the type strain SR45(T) ( = NBRC 109411(T) = DSM 26801(T)).

Desulfotomaculum peckii sp. nov., a moderately thermophilic member of the genus Desulfotomaculum, isolated from an upflow anaerobic filter treating abattoir wastewaters.

A novel anaerobic thermophilic sulfate-reducing bacterium designated strain LINDBHT1(T) was isolated from an anaerobic digester treating abattoir wastewaters in Tunisia. Strain LINDBHT1(T) grew at temperatures between 50 and 65 °C (optimum 55-60 °C), and at pH between 5.9 and 9.2 (optimum pH 6.0-6.8). Strain LINDBHT1(T) required salt for growth (1-40 g NaCl l(-1)), with an optimum of 20-30 g l(-1). In the presence of sulfate as terminal electron acceptor, strain LINDBHT1(T) used H2/CO2, propanol, butanol and ethanol as carbon and energy sources but fumarate, formate, lactate and pyruvate were not utilized. Butanol was converted to butyrate, while propanol and ethanol were oxidized to propionate and acetate, respectively. Sulfate, sulfite and thiosulfate were utilized as terminal electron acceptors but elemental sulfur, iron (III), fumarate, nitrate and nitrite were not used. The G+C content of the genomic DNA was 44.4 mol%. Phylogenetic analysis of the small-subunit rRNA gene sequence indicated that strain LINDBHT1(T) was affiliated to the genus Desulfotomaculum with the type strains of Desulfotomaculum halophilum and Desulfotomaculum alkaliphilum as its closest phylogenetic relatives (about 89% similarity). This strain represents a novel species of the genus Desulfotomaculum, Desulfotomaculum peckii sp. nov.; the type strain is LINDBHT1(T) (=DSM 23769(T)=JCM 17209(T)).

Dispersal of thermophilic Desulfotomaculum endospores into Baltic Sea sediments over thousands of years.

Patterns of microbial biogeography result from a combination of dispersal, speciation and extinction, yet individual contributions exerted by each of these mechanisms are difficult to isolate and distinguish. The influx of endospores of thermophilic microorganisms to cold marine sediments offers a natural model for investigating passive dispersal in the ocean. We investigated the activity, diversity and abundance of thermophilic endospore-forming sulfate-reducing bacteria (SRB) in Aarhus Bay by incubating pasteurized sediment between 28 and 85 °C, and by subsequent molecular diversity analyses of 16S rRNA and of the dissimilatory (bi)sulfite reductase (dsrAB) genes within the endospore-forming SRB genus Desulfotomaculum. The thermophilic Desulfotomaculum community in Aarhus Bay sediments consisted of at least 23 species-level 16S rRNA sequence phylotypes. In two cases, pairs of identical 16S rRNA and dsrAB sequences in Arctic surface sediment 3000 km away showed that the same phylotypes are present in both locations. Radiotracer-enhanced most probable number analysis revealed that the abundance of endospores of thermophilic SRB in Aarhus Bay sediment was ca. 10(4) per cm(3) at the surface and decreased exponentially to 10(0) per cm(3) at 6.5 m depth, corresponding to 4500 years of sediment age. Thus, a half-life of ca. 300 years was estimated for the thermophilic SRB endospores deposited in Aarhus Bay sediments. These endospores were similarly detected in the overlying water column, indicative of passive dispersal in water masses preceding sedimentation. The sources of these thermophiles remain enigmatic, but at least one source may be common to both Aarhus Bay and Arctic sediments.

Desulfotomaculum defluvii sp. nov., a sulfate-reducing bacterium isolated from the subsurface environment of a landfill.

A novel sulfate-reducing, strictly anaerobic and endospore-forming bacterium, designated strain A5LFS102(T), was isolated from a subsurface landfill sample. The strain was characterized using a polyphasic approach. Optimal growth was observed at 37 °C and pH 7.5 with sulfate as an electron acceptor. Sulfite and thiosulfate were utilized as electron acceptors. The respiratory isoprenoid quinone was menaquinone MK-7. 16S rRNA gene sequence analysis assigned strain A5LFS102(T) to the genus Desulfotomaculum. Both 16S rRNA and dissimilatory sulfate reductase (dsr) genes were compared with those of representative members of the genus Desulfotomaculum. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain A5LFS102(T) was closely related to Desulfotomaculum aeronauticum DSM 10349(T) (94.6% sequence similarity). The G+C content of the DNA was 45.4 mol%. The total cellular fatty acid profile was dominated by C16 fatty acids. These phenotypic and genotypic data showed that strain A5LFS102(T) should be recognized as representative of a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum defluvii sp. nov. is proposed. The type strain is A5LFS102(T) (=DSM 23699(T)=JCM 14036(T)=MTCC 7767(T)).

Desulfotomaculum hydrothermale sp. nov., a thermophilic sulfate-reducing bacterium isolated from a terrestrial Tunisian hot spring.

A novel strictly anaerobic, moderately thermophilic, sulfate-reducing bacterium, designated strain Lam5(T), was isolated from a hot spring in north-east Tunisia and was characterized phenotypically and phylogenetically. The isolate stained Gram-negative but had a Gram-positive-type cell wall. The strain comprised endospore-forming, slightly curved rod-shaped cells with peritrichous flagella. It did not possess desulfoviridin. Strain Lam5(T) grew anaerobically at 40-60 degrees C (optimally at 55 degrees C) and at pH 5.8-8.2 (optimally at pH 7.1); it did not require NaCl but tolerated concentrations up to 1.5 % (w/v). It utilized lactate, pyruvate, formate, ethanol, butanol, glycerol, propanol and H(2) (plus acetate) as electron donors. Lactate was oxidized and pyruvate was fermented to acetate. Sulfate, sulfite, thiosulfate, As(V) and Fe(III) (but not elemental sulfur, fumarate, nitrate or nitrite) were used as electron acceptors. The G+C content of the genomic DNA was 46.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing showed that strain Lam5(T) was a member of the genus Desulfotomaculum, with Desulfotomaculum putei as its closest relative (96 % similarity to the type strain). On the basis of genotypic, phenotypic and phylogenetic data, strain Lam5(T) represents a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum hydrothermale sp. nov. is proposed. The type strain is Lam5(T) (=DSM 18033(T) =JCM 13992(T)).

Desulfotomaculum alcoholivorax sp. nov., a moderately thermophilic, spore-forming, sulfate-reducer isolated from a fluidized-bed reactor treating acidic metal- and sulfate-containing wastewater.

A moderately thermophilic, Gram-positive, endospore-forming, sulfate-reducing bacterium was isolated from a fluidized-bed reactor treating acidic water containing metal and sulfate. The strain, designated RE35E1T, was rod-shaped and motile. The temperature range for growth was 33-51 degrees C (optimum 44-46 degrees C) and the pH range was 6.0-7.5 (optimum pH 6.4-7.3). The strain grew optimally without additional NaCl. The electron acceptors were 10 mM sulfate, thiosulfate and elemental sulfur and 1 mM (but not 10 mM) sulfite. Various alcohols and carboxylic acids were utilized as electron donors. Fermentative growth occurred on pyruvate. The cell wall contained meso-diaminopimelic acid, and the major respiratory isoprenoid quinone was menaquinone MK-7. The major whole-cell fatty acids were iso-C15 : 0, iso-C17 : 1 omega 10c and iso-C17 : 0. Strain RE35E1T was related to representatives of the genera Desulfotomaculum and Sporotomaculum, the closest relatives being Desulfotomaculum arcticum DSM 17038T (96.3 % 16S rRNA gene sequence similarity) and Sporotomaculum hydroxybenzoicum DSM 5475T (92.0 % similarity). Strain RE35E1T represents a novel species, for which the name Desulfotomaculum alcoholivorax sp. nov. is proposed. The type strain is RE35E1T (=DSM 16058T=JCM 14019T).

Methanol utilizing Desulfotomaculum species utilizes hydrogen in a methanol-fed sulfate-reducing bioreactor.

A sulfate-reducing bacterium, strain WW1, was isolated from a thermophilic bioreactor operated at 65 degrees C with methanol as sole energy source in the presence of sulfate. Growth of strain WW1 on methanol or acetate was inhibited at a sulfide concentration of 200 mg l(-1), while on H2/CO2, no apparent inhibition occurred up to a concentration of 500 mg l(-1). When strain WW1 was co-cultured under the same conditions with the methanol-utilizing, non-sulfate-reducing bacteria, Thermotoga lettingae and Moorella mulderi, both originating from the same bioreactor, growth and sulfide formation were observed up to 430 mg l(-1). These results indicated that in the co-cultures, a major part of the electron flow was directed from methanol via H2/CO2 to the reduction of sulfate to sulfide. Besides methanol, acetate, and hydrogen, strain WW1 was also able to use formate, malate, fumarate, propionate, succinate, butyrate, ethanol, propanol, butanol, isobutanol, with concomitant reduction of sulfate to sulfide. In the absence of sulfate, strain WW1 grew only on pyruvate and lactate. On the basis of 16S rRNA analysis, strain WW1 was most closely related to Desulfotomaculum thermocisternum and Desulfotomaculum australicum. However, physiological properties of strain WW1 differed in some aspects from those of the two related bacteria.

Desulfotomaculum thermosubterraneum sp. nov., a thermophilic sulfate-reducer isolated from an underground mine located in a geothermally active area.

A thermophilic, Gram-positive, endospore-forming, sulfate-reducing bacterium was isolated from an underground mine in a geothermally active area in Japan. Cells of this strain, designated RL50JIIIT, were rod-shaped and motile. The temperature range for growth was 50-72 degrees C (optimum growth at 61-66 degrees C) and the pH range was 6.4-7.8 (optimum at pH 7.2-7.4). Strain RL50JIIIT tolerated up to 1.5% NaCl, but optimum growth occurred in the presence of 0-1% NaCl. Electron acceptors utilized were sulfate, sulfite, thiosulfate and elemental sulfur. Electron donors utilized were H2 in the presence of CO2, alanine, various carboxylic acids and alcohols. Fermentative growth occurred on lactate and pyruvate. The cell wall contained mesodiaminopimelic acid and the major respiratory isoprenoid quinone was menaquinone 7 (MK-7). Major whole-cell fatty acids were iso-C15:0, iso-C17:0 DMA (dimethyl acetal), iso-C15:0 DMA and iso-C17:0. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed 98.7% similarity with Desulfotomaculum solfataricum DSM 14956T. However, DNA-DNA hybridization experiments with Desulfotomaculum kuznetsovii, Desulfotomaculum luciae and D. solfataricum and the G+C content of the DNA (54.4 mol%) allowed the differentiation of strain RL50JIIIT from the recognized species of the genus Desulfotomaculum. Strain RL50JIIIT therefore represents a novel species, for which the name Desulfotomaculum thermosubterraneum sp. nov. is proposed. The type strain is RL50JIIIT (=DSM 16057T=JCM 13837T).

[Detection of SRPs in injection water of Shenli Oil Field by FISH].

Fluorescence in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes was applied for analyzing the structure of sulfate reducing prokaryotes (SRPs) community in injection water of Shengli Oil Field. Eight probes and their various combinations were used to detect SRPs in the water. Results showed SRPs detected in the water were diverse, which followed in 4 bacterial phyla and 1 archaeal phylum. Total amount of SRPs was 2.86 x 10(4) cells/mL, accounting for 20% of total cells of microorganisms in the water of the Oil Field. Desulfovibrio and Desulfotomaculum cells were about 8.71% (+/- 4.45%) and 12.15% (+/- 3.90%) of the total microbial cells respectively, being dominant in the water. The relative amounts of SRPs belonging to Desulfobacterales and Syntrophobacterales, Thermodesulfobacteriales, and Thermodesulfovibro to total microbial cells in the water were 7.59% (+/- 2.92%), 3.57% (+/- 1.39%) and 2.32% (+/- 0.80%) respectively. In addition, SRPs belonging to Archaeoglobus were also detected with the amount of 4.29% (+/- 1.75%) of total microbial cells, which tells that archeal SRPs are also very important sulfate reducing microorganisms in the injection water of oil field.

Novel thermophilic sulfate-reducing bacteria from a geothermally active underground mine in Japan.

Thermophilic sulfate-reducing bacteria were enriched from samples obtained from a geothermal underground mine in Japan. The enrichment cultures contained bacteria affiliated with the genera Desulfotomaculum, Thermanaeromonas, Thermincola, Thermovenabulum, Moorella, "Natronoanaerobium," and Clostridium. Two novel thermophilic sulfate-reducing strains, RL50JIII and RL80JIV, affiliated with the genera Desulfotomaculum and Thermanaeromonas, respectively, were isolated.

Desulfotomaculum arcticum sp. nov., a novel spore-forming, moderately thermophilic, sulfate-reducing bacterium isolated from a permanently cold fjord sediment of Svalbard.

Strain 15T is a novel spore-forming, sulfate-reducing bacterium isolated from a permanently cold fjord sediment of Svalbard. Sulfate could be replaced by sulfite or thiosulfate. Hydrogen, formate, lactate, propionate, butyrate, hexanoate, methanol, ethanol, propanol, butanol, pyruvate, malate, succinate, fumarate, proline, alanine and glycine were used as electron donors in the presence of sulfate. Growth occurred with pyruvate as sole substrate. Optimal growth was observed at pH 7.1-7.5 and concentrations of 1-1.5 % NaCl and 0.4 % MgCl2. Strain 15T grew between 26 and 46.5 degrees C and optimal growth occurred at 44 degrees C. Therefore, strain 15T apparently cannot grow at in situ temperatures of Arctic sediments from where it was isolated, and it was proposed that it was present in the sediment in the form of spores. The DNA G+C content was 48.9 mol%. Strain 15T was most closely related to Desulfotomaculum thermosapovorans MLF(T) (93.5 % 16S rRNA gene sequence similarity). Strain 15T represents a novel species, for which the name Desulfotomaculum arcticum sp. nov. is proposed. The type strain is strain 15T (=DSM 17038T = JCM 12923T).

Non-sulfate-reducing, syntrophic bacteria affiliated with desulfotomaculum cluster I are widely distributed in methanogenic environments.

The classical perception of members of the gram-positive Desulfotomaculum cluster I as sulfate-reducing bacteria was recently challenged by the isolation of new representatives lacking the ability for anaerobic sulfate respiration. For example, the two described syntrophic propionate-oxidizing species of the genus Pelotomaculum form the novel Desulfotomaculum subcluster Ih. In the present study, we applied a polyphasic approach by using cultivation-independent and culturing techniques in order to further characterize the occurrence, abundance, and physiological properties of subcluster Ih bacteria in low-sulfate, methanogenic environments. 16S rRNA (gene)-based cloning, quantitative fluorescence in situ hybridization, and real-time PCR analyses showed that the subcluster Ih population composed a considerable part of the Desulfotomaculum cluster I community in almost all samples examined. Additionally, five propionate-degrading syntrophic enrichments of subcluster Ih bacteria were successfully established, from one of which the new strain MGP was isolated in coculture with a hydrogenotrophic methanogen. None of the cultures analyzed, including previously described Pelotomaculum species and strain MGP, consumed sulfite, sulfate, or organosulfonates. In accordance with these phenotypic observations, a PCR-based screening for dsrAB (key genes of the sulfate respiration pathway encoding the alpha and beta subunits of the dissimilatory sulfite reductase) of all enrichments/(co)cultures was negative with one exception. Surprisingly, strain MGP contained dsrAB, which were transcribed in the presence and absence of sulfate. Based on these and previous findings, we hypothesize that members of Desulfotomaculum subcluster Ih have recently adopted a syntrophic lifestyle to thrive in low-sulfate, methanogenic environments and thus have lost their ancestral ability for dissimilatory sulfate/sulfite reduction.

Diversity of the dsrAB (dissimilatory sulfite reductase) gene sequences retrieved from two contrasting mudflats of the Seine estuary, France.

The diversity of sulfate-reducing microorganisms was investigated in two contrasting mudflats of the Seine estuary, by PCR amplification, cloning and sequencing of the genes coding for parts of the alpha and beta subunits of dissimilatory sulfite reductase (dsrAB). One site is located in the mixing-zone and shows marine characteristics, with high salinity and sulfate concentration, whereas the other site shows freshwater characteristics, with low salinity and sulfate concentration. Diversity and abundance of dsrAB genes differed between the two sites. In the mixing-zone sediments, most of the dsrAB sequences were affiliated to those of marine Gram-negative bacteria belonging to the order of Desulfobacterales, whereas in the freshwater sediments, a majority of dsrAB sequences was related to those of the Gram-positive bacteria belonging to the genus Desulfotomaculum. It is speculated that this is related to the salinity and the sulfate concentration in the two mudflats.

Desulfotomaculum and Methanobacterium spp. dominate a 4- to 5-kilometer-deep fault.

Alkaline, sulfidic, 54 to 60 degrees C, 4 to 53 million-year-old meteoric water emanating from a borehole intersecting quartzite-hosted fractures >3.3 km beneath the surface supported a microbial community dominated by a bacterial species affiliated with Desulfotomaculum spp. and an archaeal species related to Methanobacterium spp. The geochemical homogeneity over the 650-m length of the borehole, the lack of dividing cells, and the absence of these microorganisms in mine service water support an indigenous origin for the microbial community. The coexistence of these two microorganisms is consistent with a limiting flux of inorganic carbon and SO4(2-) in the presence of high pH, high concentrations of H2 and CH4, and minimal free energy for autotrophic methanogenesis. Sulfide isotopic compositions were highly enriched, consistent with microbial SO4(2-) reduction under hydrologic isolation. An analogous microbial couple and similar abiogenic gas chemistry have been reported recently for hydrothermal carbonate vents of the Lost City near the Mid-Atlantic Ridge (D. S. Kelly et al., Science 307:1428-1434, 2005), suggesting that these features may be common to deep subsurface habitats (continental and marine) bearing this geochemical signature. The geochemical setting and microbial communities described here are notably different from microbial ecosystems reported for shallower continental subsurface environments.

Desulfotomaculum carboxydivorans sp. nov., a novel sulfate-reducing bacterium capable of growth at 100% CO.

A moderately thermophilic, anaerobic, chemolithoheterotrophic, sulfate-reducing bacterium, strain CO-1-SRB(T), was isolated from sludge from an anaerobic bioreactor treating paper mill wastewater. Cells were Gram-positive, motile, spore-forming rods. The temperature range for growth was 30-68 degrees C, with an optimum at 55 degrees C. The NaCl concentration range for growth was 0-17 g l(-1); there was no change in growth rate until the NaCl concentration reached 8 g l(-1). The pH range for growth was 6.0-8.0, with an optimum of 6.8-7.2. The bacterium could grow with 100% CO in the gas phase. With sulfate, CO was converted to H(2) and CO(2) and part of the H(2) was used for sulfate reduction; without sulfate, CO was completely converted to H(2) and CO(2). With sulfate, strain CO-1-SRB(T) utilized H(2)/CO(2), pyruvate, glucose, fructose, maltose, lactate, serine, alanine, ethanol and glycerol. The strain fermented pyruvate, lactate, glucose and fructose. Yeast extract was necessary for growth. Sulfate, thiosulfate and sulfite were used as electron acceptors, whereas elemental sulfur and nitrate were not. A phylogenetic analysis of 16S rRNA gene sequences placed strain CO-1-SRB(T) in the genus Desulfotomaculum, closely resembling Desulfotomaculum nigrificans DSM 574(T) and Desulfotomaculum sp. RHT-3 (99 and 100% similarity, respectively). However, the latter strains were completely inhibited above 20 and 50% CO in the gas phase, respectively, and were unable to ferment CO, lactate or glucose in the absence of sulfate. DNA-DNA hybridization of strain CO-1-SRB(T) with D. nigrificans and Desulfotomaculum sp. RHT-3 showed 53 and 60% relatedness, respectively. On the basis of phylogenetic and physiological features, it is suggested that strain CO-1-SRB(T) represents a novel species within the genus Desulfotomaculum, for which the name Desulfotomaculum carboxydivorans is proposed. This is the first description of a sulfate-reducing micro-organism that is capable of growth under an atmosphere of pure CO with and without sulfate. The type strain is CO-1-SRB(T) (=DSM 14880(T)=VKM B-2319(T)).

Isolation of sulfate-reducing bacteria from the terrestrial deep subsurface and description of Desulfovibrio cavernae sp. nov.

Deep subsurface sandstones in the area of Berlin (Germany) located 600 to 1060 m below the surface were examined for the presence of viable microorganisms. The in situ temperatures at the sampling sites ranged from 37 to 45 degrees C. Investigations focussed on sulfate-reducing bacteria able to grow on methanol and triethylene glycol, which are added as chemicals to facilitate the long-term underground storage of natural gas. Seven strains were isolated from porewater brines in the porous sandstone. Three of them were obtained with methanol (strains H1M, H3M, and B1M), three strains with triethylene glycol (strains H1T, B1T, and B2T) and one strain with a mixture of lactate, acetate and butyrate (strain H1-13). Due to phenotypic properties six isolates could be identified as members of the genus Desulfovibrio, and strain B2T as a Desulfotomaculum. The salt tolerance and temperature range for growth indicated that the isolates originated from the indigenous deep subsurface sandstones. They grew in mineral media reflecting the in situ ionic composition of the different brines, which contained 1.5 to 190 g NaCl x l(-1) and high calcium and magnesium concentrations. The Desulfovibrio strains grew at temperatures between 20 and 50 degrees C, while the Desulfotomaculum strain was thermophilic and grew between 30 and 65 degrees C. The strains utilized a broad spectrum of electron donors and acceptors. They grew with carbon compounds like lactate, pyruvate, formate, n-alcohols (C1-C5), glycerol, ethylene glycol, malate, succinate, and fumarate. Some strains even utilized glucose as electron donor and carbon source. All strains were able to use sulfate, sulfite and nitrate as electron acceptors. Additionally, three Desulfovibrio strains reduced manganese oxide, the Desulfotomaculum strain reduced manganese oxide, iron oxide, and elemental sulfur. The 16S rRNA analysis revealed that the isolates belong to three different species. The strains H1T, H3M and B1M could be identified as Desulfovibrio indonesiensis, and strain B2T as Desulfotomaculum geothermicum. The other Desulfovibrio strains (H1M, H1-13, and B1T) showed identical 16S rDNA sequences and similarities as low as 93% to their closest relative, Desulfovibrio aminophilusT. Therefore, these isolates were assigned to a new species, Desulfovibrio cavernae sp. nov., with strain H1M as the type strain.

Microbial community structure in a thermophilic anaerobic hybrid reactor degrading terephthalate.

A thermophilic terephthalate-degrading methanogenic consortium was successfully enriched for 272 days in an anaerobic hybrid reactor, and the microbial structure was characterized using terminal RFLPs, clone libraries and fluorescence in-situ hybridization with rRNA-targeted oligonucleotide probes. All the results suggested that Methanothrix thermophila-related methanogens, Desulfotomaculum-related bacterial populations in the Gram-positive low-G + C group, and OP5-related populations were the key members responsible for terephthalate degradation under thermophilic methanogenic conditions except during periods when the reactor experienced heat shock and pump failure. These perturbations caused a significant shift in bacterial population structure in sludge samples taken from the sludge bed but not from the surface of the packing materials. After system recovery, many other bacterial populations emerged, which belonged mainly to the Gram-positive low-G + C group and Cytophaga-Flexibacter-Bacteroides, as well as beta-Proteobacteria, Planctomycetes and Nitrospira. These newly emerged populations were probably also capable of degrading terephthalate in the hybrid system, but were out-competed by those bacterial populations before perturbations.