Biomedical subjects

Ken Takai

Publications and source records attributed to Ken Takai.

At least 19 recordsLinked to original sources

PubMed2007

Extremely high alkaline protease from a deep-subsurface bacterium, Alkaliphilus transvaalensis.

A new high-alkaline protease (ALTP) was purified to homogeneity from a culture of the strictly anaerobic and extremely alkaliphilic Alkaliphilus transvaalensis. The molecular mass was 30 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme showed the maximal caseinolytic activity higher than pH 12.6 in KCl-NaOH buffer at 40 degrees C. Hydrolysis of the oxidized insulin B-chain followed by mass spectrometric analysis of the cleaved products revealed that as many as 24 of the total 29 peptide bonds are hydrolyzed in a block-cutting manner, suggesting that ALTP has a widespread proteolytic functions. Calcium ion had no effect on the activity and stability of ALTP, unlike known subtilisins. The deduced amino acid sequence of the enzyme comprised 279 amino acids plus 97 prepropeptide amino acids. The amino acid sequence of mature ALTP was confirmed by capillary liquid chromatography coupled to tandem mass spectrometry, which was the 93% coverage of the deduced amino acid sequence. The mature enzyme showed moderate homology to subtilisin LD1 from the alkaliphilic Bacillus sp. strain KSM-LD1 with 64% identity, and both enzymes formed a new subcluster at an intermediate position among true subtilisins and high-alkaline proteases in a phylogenetic tree of subtilase family A. ALTP is the first high-alkaline protease reported from a strict anaerobe in this family.

Amino Acid Sequence↗

PubMed2006

Microbial community in a sediment-hosted CO2 lake of the southern Okinawa Trough hydrothermal system.

Increasing levels of CO2 in the atmosphere are expected to cause climatic change with negative effects on the earth's ecosystems and human society. Consequently, a variety of CO2 disposal options are discussed, including injection into the deep ocean. Because the dissolution of CO2 in seawater will decrease ambient pH considerably, negative consequences for deep-water ecosystems have been predicted. Hence, ecosystems associated with natural CO2 reservoirs in the deep sea, and the dynamics of gaseous, liquid, and solid CO2 in such environments, are of great interest to science and society. We report here a biogeochemical and microbiological characterization of a microbial community inhabiting deep-sea sediments overlying a natural CO2 lake at the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough. We found high abundances (>10(9) cm(-3)) of microbial cells in sediment pavements above the CO2 lake, decreasing to strikingly low cell numbers (10(7) cm(-3)) at the liquid CO2/CO2-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur-metabolizing chemolithotrophs within the Gamma- and Epsilonproteobacteria. The detection of functional genes related to one-carbon assimilation and the presence of highly 13C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO2 and/or CH4 dominate the liquid CO2 and CO2-hydrate-bearing sediments. Clearly, the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO2 disposal as well as of natural CO2 reservoirs as potential microbial habitats on early Earth and other celestial bodies.

Archaea↗

PubMed2006

Microbial community in black rust exposed to hot ridge flank crustal fluids.

During Integrated Ocean Drilling Program Expedition 301, we obtained a sample of black rust from a circulation obviation retrofit kit (CORK) observatory at a borehole on the eastern flank of Juan de Fuca Ridge. Due to overpressure, the CORK had failed to seal the borehole. Hot fluids from oceanic crust had discharged to the overlying bottom seawater and resulted in the formation of black rust analogous to a hydrothermal chimney deposit. Both culture-dependent and culture-independent analyses indicated that the black-rust-associated community differed from communities reported from other microbial habitats, including hydrothermal vents at seafloor spreading centers, while it shared phylotypes with communities previously detected in crustal fluids from the same borehole. The most frequently retrieved sequences of bacterial and archaeal 16S rRNA genes were related to the genera Ammonifex and Methanothermococcus, respectively. Most phylotypes, including phylotypes previously detected in crustal fluids, were isolated in pure culture, and their metabolic traits were determined. Quantification of the dissimilatory sulfite reductase (dsrAB) genes, together with stable sulfur isotopic and electron microscopic analyses, strongly suggested the prevalence of sulfate reduction, potentially by the Ammonifex group of bacteria. Stable carbon isotopic analyses suggested that the bulk of the microbial community was trophically reliant upon photosynthesis-derived organic matter. This report provides important insights into the phylogenetic, physiological, and trophic characteristics of subseafloor microbial ecosystems in warm ridge flank crusts.

Archaea↗

PubMed2006

Biogeographical distribution and diversity of microbes in methane hydrate-bearing deep marine sediments on the Pacific Ocean Margin.

The deep subseafloor biosphere is among the least-understood habitats on Earth, even though the huge microbial biomass therein plays an important role for potential long-term controls on global biogeochemical cycles. We report here the vertical and geographical distribution of microbes and their phylogenetic diversities in deeply buried marine sediments of the Pacific Ocean Margins. During the Ocean Drilling Program Legs 201 and 204, we obtained sediment cores from the Peru and Cascadia Margins that varied with respect to the presence of dissolved methane and methane hydrate. To examine differences in prokaryotic distribution patterns in sediments with or without methane hydrates, we studied >2,800 clones possessing partial sequences (400-500 bp) of the 16S rRNA gene and 348 representative clone sequences (approximately 1 kbp) from the two geographically separated subseafloor environments. Archaea of the uncultivated Deep-Sea Archaeal Group were consistently the dominant phylotype in sediments associated with methane hydrate. Sediment cores lacking methane hydrates displayed few or no Deep-Sea Archaeal Group phylotypes. Bacterial communities in the methane hydrate-bearing sediments were dominated by members of the JS1 group, Planctomycetes, and Chloroflexi. Results from cluster and principal component analyses, which include previously reported data from the West and East Pacific Margins, suggest that, for these locations in the Pacific Ocean, prokaryotic communities from methane hydrate-bearing sediment cores are distinct from those in hydrate-free cores. The recognition of which microbial groups prevail under distinctive subseafloor environments is a significant step toward determining the role these communities play in Earth's essential biogeochemical processes.

Archaea↗

PubMed2006

The versatile epsilon-proteobacteria: key players in sulphidic habitats.

The epsilon-proteobacteria have recently been recognized as globally ubiquitous in modern marine and terrestrial ecosystems, and have had a significant role in biogeochemical and geological processes throughout Earth's history. To place this newly expanded group, which consists mainly of uncultured representatives, in an evolutionary context, we present an overview of the taxonomic classification for the class, review ecological and metabolic data in key sulphidic habitats and consider the ecological and geological potential of the epsilon-proteobacteria in modern and ancient systems. These integrated perspectives provide a framework for future culture- and genomic-based studies.

Biodiversity↗

PubMed2006

Sulfurimonas paralvinellae sp. nov., a novel mesophilic, hydrogen- and sulfur-oxidizing chemolithoautotroph within the Epsilonproteobacteria isolated from a deep-sea hydrothermal vent polychaete nest, reclassification of Thiomicrospira denitrificans as Sulfurimonas denitrificans comb. nov. and emended description of the genus Sulfurimonas.

A novel mesophilic bacterium, strain GO25(T), was isolated from a nest of hydrothermal vent polychaetes, Paralvinella sp., at the Iheya North field in the Mid-Okinawa Trough. Cells were motile short rods with a single polar flagellum. Growth was observed between 4 and 35 degrees C (optimum 30 degrees C; 13-16 h doubling time) and between pH 5.4 and 8.6 (optimum pH 6.1). The isolate was a facultatively anaerobic chemolithoautotroph capable of growth using molecular hydrogen, elemental sulfur or thiosulfate as the sole energy source, carbon dioxide as the sole carbon source, ammonium or nitrate as the sole nitrogen source and elemental sulfur, thiosulfate or yeast extract as the sole sulfur source. Strain GO25(T) represents the first deep-sea epsilonproteobacterium capable of growth by both hydrogen and sulfur oxidation. Nitrate or molecular oxygen (up to 10 % partial pressure) could serve as the sole electron acceptor to support growth. Metabolic products of nitrate reduction shifted in response to the electron donor provided. The G+C content of genomic DNA was 37.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolate belonged to the genus Sulfurimonas and was most closely related to Sulfurimonas autotrophica OK10(T) (96.3 % sequence similarity). DNA-DNA hybridization demonstrated that the novel isolate could be differentiated genotypically from Sulfurimonas autotrophica OK10(T). On the basis of the physiological and molecular properties of the novel isolate, the name Sulfurimonas paralvinellae sp. nov. is proposed, with strain GO25(T) (=JCM 13212(T)=DSM 17229(T)) as the type strain. Thiomicrospira denitrificans DSM 1251(T) (=ATCC 33889(T)) is phylogenetically associated with Sulfurimonas autotrophica OK10(T) and Sulfurimonas paralvinellae GO25(T). Based on the phylogenetic relationship between Thiomicrospira denitrificans DSM 1251(T), Sulfurimonas autotrophica OK10(T) and Sulfurimonas paralvinellae GO25(T), we propose the reclassification of Thiomicrospira denitrificans as Sulfurimonas denitrificans comb. nov. (type strain DSM 1251(T)=ATCC 33889(T)). In addition, an emended description of the genus Sulfurimonas is proposed.

Anaerobiosis↗

PubMed2006

Sulfurivirga caldicuralii gen. nov., sp. nov., a novel microaerobic, thermophilic, thiosulfate-oxidizing chemolithoautotroph, isolated from a shallow marine hydrothermal system occurring in a coral reef, Japan.

Novel thermophilic bacteria, designated strains VW1 and MM1(T), were isolated from hydrothermal fluid and microbial mat samples, respectively, collected from a shallow marine hydrothermal system (water depth 22 m) occurring in coral reefs off Taketomi Island, Okinawa, Japan. Cells of the two novel strains were motile rods with a single polar flagellum in the exponential growth phase. In a medium that included elemental sulfur, cells of the two strains became non-motile with oval to spherical cell shapes. For both strains, growth occurred at between 30 and 60 degrees C (optimum temperature of 50-55 degrees C; 60-80 min doubling time) and between pH 5.5 and 7.1 (optimum pH 6.0). The isolates were microaerobic chemolithoautotrophs capable of using thiosulfate or tetrathionate as the sole energy source, O(2) as the sole electron acceptor and CO(2) as the sole carbon source. Organic substrates, such as yeast extract and tryptone, inhibited growth of both strains. The G+C contents of genomic DNA were 51.3 and 49.5 mol% for strains VW1 and MM1(T), respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the two strains were closely related to each other (99.9 % sequence similarity) and were distantly related to other previously described genera within the Gammaproteobacteria. The novel isolates could also be differentiated from other gammaproteobacterial genera on the basis of their physiological properties. It is suggested that the novel isolates represent the type species of a new genus, for which the name Sulfurivirga caldicuralii gen. nov., sp. nov. (type strain MM1(T)=JCM 13439(T)=DSM 17737(T)) is proposed.

Animals↗

PubMed2006

Molecular analysis of deep subsurface Cretaceous rock indicates abundant Fe(III)- and S(zero)-reducing bacteria in a sulfate-rich environment.

A multilevel sampler (MLS) was emplaced in a borehole straddling anaerobic, sulfate-rich Cretaceous-era shale and sandstone rock formations approximately 200 m below ground surface at Cerro Negro, New Mexico. Sterile quartzite sand contained in chambers in the sampler allowed in situ colonization and recovery of nucleic acids for molecular analyses. Denaturing gradient gel electrophoresis and 16S rRNA gene cloning results indicated a homogeneously distributed bacterial community across the shale-sandstone interface. delta-Proteobacteria sequences were common at all depths, and were dominated by members of the Geobacteraceae family (Pelobacter, Desulphuromonas and Geobacter). Other members of this group are capable of dissimilatory Fe(III) and/or S degrees reduction, but not sulfate reduction. RNA hybridization data also suggested that Fe(III)-/S degrees -reducing bacteria were predominant. These findings are striking considering the lack of significant concentrations of these electron acceptors in this environment. The next most abundant bacterial group indicated was the sulfate reducers, including Desulfobacterium, Desulfocapsa and Desulfobulbus. Sequences related to fermenters, denitrifiers and acetogens were also recovered. The presence of a phylogenetically and functionally diverse microbial community in this deep subsurface environment likely reflects the complex nature of the primary energy and carbon sources, kerogen associated with the shale.

Base Sequence↗

PubMed2006

Geomicrobiological exploration and characterization of a novel deep-sea hydrothermal system at the TOTO caldera in the Mariana Volcanic Arc.

Novel hydrothermal activities accompanying effluent white smokers and elemental sulfur chimney structures at the north-east lava dome of the TOTO caldera depression in the Mariana Volcanic Arc have been explored and characterized by geochemical and microbiological surveys. White smoker hydrothermal fluids were observed in the potential hydrothermal activity centre of the field and represented the maximal temperature of 170 degrees C and the lowest pH of 1.6. The chimney structures, all consisting of elemental sulfur (sulfur chimney), were also unique to the TOTO caldera hydrothermal field. Microbial community structures in a sulfur chimney and its formation hydrothermal fluid with a high concentration of hydrogen sulfide (15 mM) have been investigated by culture-dependent and -independent analyses. 16S rRNA gene clone analysis and fluorescence in situ hybridization (FISH) analysis revealed that epsilon-Proteobacteria dominated the microbial communities in the sulfur chimney structure and formed a dense microbial mat covering the sulfur chimney surface. Archaeal phylotypes were consistently minor components in the communities and related to the genera Thermococcus, Pyrodictium, Aeropyrum, and the uncultivated archaeal group of 'deep-sea hydrothermal vent euryarchaeotal group'. Cultivation analysis suggested that the chemolithoautotrophs might play a significant ecological role as primary producers utilizing gas and sulfur compounds provided from hydrothermal fluids.

Archaea↗

PubMed2006

Quantification of mcrA by quantitative fluorescent PCR in sediments from methane seep of the Nankai Trough.

A quantitative fluorogenic PCR method for group-specific methyl coenzyme M reductase subunit A genes (mcrA) from methanotrophic archaea was established and applied to the characterization of microbial communities in anoxic methane seep sediments at the accretionary prism of the Nankai Trough. All of the previously identified subgroups of anaerobic methanotroph (ANME) mcrA genes were detected in the cores up to 25 cm below the seafloor, but distributional patterns of mcrA genes were found to differ according to depth. These findings suggest a distinct distribution of phylogenetically and physiologically diverse methanotrophic archaea that mediate methane oxidation in the anoxic sediments. This quantification method will contribute to future investigations of methanotrophic microbial ecosystems in anoxic marine sediments.

Anaerobiosis↗

PubMed2006

Host-symbiont relationships in hydrothermal vent gastropods of the genus Alviniconcha from the Southwest Pacific.

Hydrothermal vent gastropods of the genus Alviniconcha are unique among metazoans in their ability to derive their nutrition from chemoautotrophic gamma- and epsilon-proteobacterial endosymbionts. Although host-symbiont relationships in Alviniconcha gastropods from the Central Indian Ridge in the Indian Ocean and the Mariana Trough in the Western Pacific have been studied extensively, host-symbiont relationships in Alviniconcha gastropods from the Southwest Pacific remain largely unknown. Phylogenetic analysis using mitochondrial cytochrome c oxidase subunit I gene sequences of host gastropods from the Manus, North Fiji, and Lau Back-Arc Basins in the Southwest Pacific has revealed a new host lineage in a Alviniconcha gastropod from the Lau Basin and the occurrence of the host lineage Alviniconcha sp. type 2 in the Manus Basin. Based on 16S rRNA gene sequences of bacterial endosymbionts, two gamma-proteobacterial lineages and one epsilon-proteobacterial lineage were identified in the present study. The carbon isotopic compositions of the biomass and fatty acids of the gastropod tissues suggest that the gamma- and epsilon-proteobacterial endosymbionts mediate the Calvin-Benson cycle and the reductive tricarboxylic acid cycle, respectively, for their chemoautotrophic growth. Coupling of the host and symbiont lineages from the three Southwest Pacific basins revealed that each of the Alviniconcha lineages harbors different bacterial endosymbionts belonging to either the gamma- or epsilon-Proteobacteria. The host specificity exhibited in symbiont selection provides support for the recognition of each of the host lineages as a distinct species. The results from the present study also suggest the possibility that Alviniconcha sp. types 1 and 2 separately inhabit hydrothermal vent sites approximately 120 m apart in the North Fiji Basin and 500 m apart in the Manus Basin.

Animals↗

PubMed2005

Variability in microbial community and venting chemistry in a sediment-hosted backarc hydrothermal system: Impacts of subseafloor phase-separation.

Phase-separation and -segregation (boiling/distillation of subseafloor hydrothermal fluids) represent the primary mechanisms causing intra-field variations in vent fluid compositions. To determine whether this geochemical process affects the formation of microbial communities, we examined the microbial communities at three different vent sites located within a few tens meters of one another. In addition to chimney structures, colonization devices capturing subseafloor communities entrained by the vent fluids were studied, using culture-dependent and -independent methods. Microbiological analyses demonstrated the occurrence of distinctive microbial communities in each of the hydrothermal niches. Within a chimney structure, there was a transition from a mixed community of mesophiles and thermophiles in the exterior parts to thermophiles in the interior. Beside the transition within a chimney structure, intra-field variations in microbial communities in vent fluids were apparent. Geochemical analysis demonstrated that different vent fluids have distinctive end-member compositions as a consequence of subseafloor phase-separation and -segregation, which were designated gas-depleted, normal and gas-enriched fluids. In comparison to gas-depleted and normal fluids, gas-enriched fluids harbored more abundant chemolithoautotrophs with gaseous component-dependent energy metabolism, such as hydrogenotrophic methanogenesis. Subseafloor phase-separation and -segregation may play a key role in supplying energy and carbon sources to vent-associated chemolithoautotrophs and subvent microbial communities.

Archaea↗

PubMed2005

Bacterial community shift along a subsurface geothermal water stream in a Japanese gold mine.

Change of bacterial community occurring along a hot water stream in the Hishikari gold mine, Japan, was investigated by applying a combination of various culture-independent techniques. The stream, which is derived from a subsurface anaerobic aquifer containing plentiful CO2, CH4, H2, and NH4+, emerges in a mine tunnel 320 m below the surface providing nutrients for a lush microbial community that extends to a distance of approximately 7 m in the absence of sunlight-irradiation. Over this distance, the temperature decreases from 69 degrees C to 55 degrees C, and the oxidation-reduction potential increases from -130 mV to +59 mV. In the hot upper reaches of the stream, the dominant phylotypes were: 1) a deeply branching lineage of thermophilic methane-oxidizing gamma-Proteobacteria, and 2) a thermophilic hydrogen- and sulfur-oxidizing Sulfurihydrogenibium sp. In contrast, the prevailing phylotypes in the middle and lower parts of the stream were closely related to ammonia-oxidizing Nitrosomonas and nitrite-oxidizing Nitrospira spp.. Changes in the microbial metabolic potential estimated by competitive PCR analysis of genes encoding the enzymes, particulate methane monooxygenase (pmoA), ammonia monooxygenase (amoA), and putative nitrite oxidoreductase (norB), also substantiated the community shift indicated by 16S rRNA gene analysis. The diversity of putative norB lineages was assessed for the first time in the hot water environment. Estimation of dominant phylotypes by whole-cell fluorescent in situ hybridization and changes in inorganic nitrogen compounds such as decreasing ammonium and increasing nitrite and nitrate in the mat-interstitial water along the stream were consistent with the observed transition of the bacterial community structure in the stream.

Ammonia↗

PubMed2005

Hydrogen-driven subsurface lithoautotrophic microbial ecosystems (SLiMEs): do they exist and why should we care?

One of the keys to success of many anaerobic ecosystems is the process of syntrophic intercellular hydrogen transfer. This process facilitates the overall reaction by end-product removal, taking advantage of a wide variety of organisms that are able to use hydrogen directly as an energy source by uptake hydrogenases. Thus, the issue is not whether there are hydrogen-driven processes or communities but whether there are hydrogen-driven communities that exist and persist independently of the products of photosynthesis (so-called subsurface lithoautotrophic microbial ecosystems, or SLiMEs). It is the proof of long-term independence from photosynthesis and its products that is the most difficult issue to establish, and perhaps the most important one with regard to searching for SLiMEs both on and off our planet. Although the evidence is not yet unequivocal, a growing body of evidence supports the existence of SLiME-like communities: if they exist, the implications are immense with regard to understanding subsurface environments on Earth, looking for present day analogs of early Earth and the search for life in other worlds.

Archaea↗

PubMed2005

Lebetimonas acidiphila gen. nov., sp. nov., a novel thermophilic, acidophilic, hydrogen-oxidizing chemolithoautotroph within the 'Epsilonproteobacteria', isolated from a deep-sea hydrothermal fumarole in the Mariana Arc.

A novel thermophilic, acidophilic bacterium, designated strain Pd55T, was isolated from a self-temperature-recording in situ colonization system deployed in a hydrothermal diffusing flow (maximum temperature of 78 degrees C) at the TOTO caldera in the Mariana Arc. Cells of strain Pd55T were motile, short rods with a single polar flagellum. Growth was observed between 30 and 68 degrees C (optimum growth at 50 degrees C; 120 min doubling time) and between (initial) pH 4.2 and 7.0 (optimum at pH 5.2). The isolate was a strictly anaerobic chemolithoautotroph capable of using molecular hydrogen as sole energy source and carbon dioxide as sole carbon source. Elemental sulfur served as the sole electron acceptor to support growth. The G+C content of the genomic DNA was 34.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate was related to members of the genera Nautilia and Caminibacter, although it appeared to be a novel lineage prior to the divergence between Nautilia and Caminibacter. Strain Pd55T could also be differentiated from Nautilia and Caminibacter species on the basis of its physiological properties. It is, therefore, proposed that strain Pd55T (=JCM 12420T=DSM 16356T) represents the type strain of a novel species in a new genus, Lebetimonas acidiphila gen. nov., sp. nov.

Anaerobiosis↗

PubMed2005

Thioreductor micantisoli gen. nov., sp. nov., a novel mesophilic, sulfur-reducing chemolithoautotroph within the epsilon-Proteobacteria isolated from hydrothermal sediments in the Mid-Okinawa Trough.

A novel mesophilic, hydrogen-oxidizing, sulfur-reducing bacterium, designated strain BKB25Ts-Y(T), was isolated from hydrothermal sediments at Iheya North in the Mid-Okinawa Trough, Japan. Cells were Gram-negative, motile rods (1.8-2.1 microm long and 0.5-0.7 microm wide). The isolate was a strictly anaerobic chemolithoautotroph capable of using molecular hydrogen as the sole energy source and carbon dioxide as the sole carbon source. Elemental sulfur and nitrate served as electron acceptors, respectively yielding hydrogen sulfide and ammonium. Growth was observed at 20-42 degrees C (optimum 32 degrees C; 3 h doubling time), pH 5.0-6.5 (optimum 6.0) and in the presence of 2.0-4.0 % NaCl (optimum 2.5 %) via respiratory S(0) reduction with H(2). The G+C content of the genomic DNA was 37.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate represented the first strain for which taxonomic properties have been characterized within the previously uncultivated epsilon-Proteobacteria Group G. On the basis of the physiological and molecular properties of the novel isolate, the genus name Thioreductor gen. nov. is proposed, with Thioreductor micantisoli sp. nov. as the type species. The type strain is BKB25Ts-Y(T) (=JCM 12457(T)=DSM 16661(T)).

Bacterial Typing Techniques↗

PubMed2005

Thiobacter subterraneus gen. nov., sp. nov., an obligately chemolithoautotrophic, thermophilic, sulfur-oxidizing bacterium from a subsurface hot aquifer.

A novel, thermophilic, obligately chemolithoautotrophic, sulfur/thiosulfate-oxidizing bacterium was isolated from subsurface geothermal aquifer water (temperature approximately 70 degrees C) in the Hishikari gold mine, Japan. Cells of the isolate, designated strain C55T, were motile, straight rods with a single polar flagellum. Growth was observed at temperatures between 35 and 62 degrees C (optimum 50-55 degrees C; 60 min doubling time) and pH between 5.2 and 7.7 (optimum pH 6.5-7.0). High growth rate of strain C55T was observed on either thiosulfate or elemental sulfur as a sole energy source, with molecular oxygen as the only electron acceptor. None of the organic compounds tested supported or stimulated growth of strain C55T. The G+C content of the genomic DNA was 66.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain C55T was affiliated to the beta-Proteobacteria, but was distantly related to recognized genera. On the basis of its physiological and molecular properties, strain C55T (=JCM12421T=DSM 16629T=ATCC BAA-941T) is proposed as the type strain of Thiobacter subterraneus gen. nov., sp. nov.

Base Composition↗

PubMed2005

Nitratiruptor tergarcus gen. nov., sp. nov. and Nitratifractor salsuginis gen. nov., sp. nov., nitrate-reducing chemolithoautotrophs of the epsilon-Proteobacteria isolated from a deep-sea hydrothermal system in the Mid-Okinawa Trough.

Two novel denitrifying bacteria, designated strains MI55-1(T) and E9I37-1(T), were isolated from deep-sea hydrothermal vent chimney structures at the Iheya North hydrothermal field in the Mid-Okinawa Trough, Japan. Both isolates were strict chemolithoautotrophs growing by respiratory nitrate reduction with H(2), forming N(2) as a metabolic product. Oxygen (at low concentrations) could serve as an alternative electron acceptor for growth of the isolates. Growth of strain MI55-1(T) was observed at temperatures between 40 and 57 degrees C (optimum, 55 degrees C; doubling time, 2 h), at pH values between 5.4 and 6.9 (optimum, pH 6.4) and in the presence of between 1.5 and 4.0 % (w/v) NaCl (optimum, 2.5 %). Growth of strain E9I37-1(T) was observed at temperatures between 28 and 40 degrees C (optimum, 37 degrees C; doubling time, 2.5 h), at pH values between 5.6 and 7.6 (optimum, pH 7.0) and in the presence of between 1.5 and 3.5 % (w/v) NaCl (optimum, 3.0 %). The G+C contents of the genomic DNA of strains MI55-1(T) and E9I37-1(T) were 29.6 and 35.5 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains MI55-1(T) and E9I37-1(T) belonged to groups A and F of the epsilon-Proteobacteria, but that they had distant phylogenetic relationships with any species, within the phylogenetic groups, that had validly published names (sequence similarities were less than 91 %). On the basis of the physiological and molecular characteristics of the novel isolates, it is proposed that they should each be classified in a novel genus: Nitratiruptor tergarcus gen. nov., sp. nov., with MI55-1(T) (=JCM 12459(T)=DSM 16512(T)) as the type strain, and Nitratifractor salsuginis gen. nov., sp. nov., with E9I37-1(T) (=JCM 12458(T)=DSM 16511(T)) as the type strain.

Bacterial Typing Techniques↗