Nitrate respiratory metabolism in an obligately autotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6

Suzuki, Miho; Cui, Zong Jie; Ishii, Masaharu; Igarashi, Yasuo

doi:10.1007/s002030000230

Cited by 29 publications

(22 citation statements)

References 20 publications

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“…In this cycle, ACL functions to harvest the fixed carbon as acetyl-CoA, and regenerates the oxaloacetate required to continue the cycle (Evans et al, 1966;Beh et al, 1993). The reductive TCA cycle and ACL activity have been reported in a phylogenetically diverse group of extremophiles, including anaerobically grown Desulfobacter hydrogenophilus (Schauder et al, 1987), the thermophilic bacteria, Hydrogenobacter thermophillus and Aquifex pyrophilus (Shiba et al, 1985;Beh et al, 1993;Suzuki et al, 2001), and the thermophilic archaeon Thermoproteus neutrophilus (Beh et al, 1993). Except for C. limicola, no ACL sequences are yet available from these organisms.…”

Section: Discussionmentioning

confidence: 99%

Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis,

Fatland¹,

Ke²,

Anderson³

et al. 2002

Plant Physiology

196

194

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Acetyl-coenzyme A (CoA) is used in the cytosol of plant cells for the synthesis of a diverse set of phytochemicals including waxes, isoprenoids, stilbenes, and flavonoids. The source of cytosolic acetyl-CoA is unclear. We identified two Arabidopsis cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase (ACL). Coexpression of these cDNAs in yeast (Saccharomyces cerevisiae) confers ACL activity, indicating that both the Arabidopsis genes are required for ACL activity. Arabidopsis ACL is a heteromeric enzyme composed of two distinct subunits, ACLA (45 kD) and ACLB (65 kD). The holoprotein has a molecular mass of 500 kD, which corresponds to a heterooctomer with an A 4 B 4 configuration. ACL activity and the ACLA and ACLB polypeptides are located in the cytosol, consistent with the lack of targeting peptides in the ACLA and ACLB sequences. In the Arabidopsis genome, three genes encode for the ACLA subunit (ACLA-1, At1g10670; ACLA-2, At1g60810; and ACLA-3, At1g09430), and two genes encode the ACLB subunit (ACLB-1, At3g06650 and ACLB-2, At5g49460). The ACLA and ACLB mRNAs accumulate in coordinated spatial and temporal patterns during plant development. This complex accumulation pattern is consistent with the predicted physiological needs for cytosolic acetyl-CoA, and is closely coordinated with the accumulation pattern of cytosolic acetyl-CoA carboxylase, an enzyme using cytosolic acetyl-CoA as a substrate. Taken together, these results indicate that ACL, encoded by the ACLA and ACLB genes of Arabidopsis, generates cytosolic acetyl-CoA. The heteromeric organization of this enzyme is common to green plants (including Chlorophyceae, Marchantimorpha, Bryopsida, Pinaceae, monocotyledons, and eudicots), species of fungi, Glaucophytes, Chlamydomonas, and prokaryotes. In contrast, all known animal ACL enzymes have a homomeric structure, indicating that a evolutionary fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom.Acetyl-coenzyme A (CoA) is an intermediate metabolite that is juxtaposed between catabolic and anabolic processes. As the entry point for the tricarboxylic acid (TCA) cycle, acetyl-CoA can be considered the gateway in the oxidation of carbon derived from the catabolism of fatty acids, certain amino acids (e.g. Leu, Ile, Lys, and Trp), and carbohydrates. Furthermore, acetyl-CoA is the intermediate precursor for the biosynthesis of a wide variety of phytochemicals. Because membranes are impermeable to CoA derivatives, it can be inferred that acetyl-CoA is generated in at least four distinct metabolic pools representing the four subcellular compartments where acetyl-CoA metabolism occurs: plastids, mitochondria, peroxisomes, and the cytosol (Fig. 1). Therefore, plants should have distinct acetyl-CoA-generating systems in mitochondria (for the TCA cycle), in plastids (for de novo fatty acid biosynthesis), in peroxisomes (the product of ␤-oxidation of fatty acids), and in the cytosol (for the biosynthesis of isoprenoids, flavo...

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Section: Discussionmentioning

confidence: 99%

Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis,

Fatland¹,

Ke²,

Anderson³

et al. 2002

Plant Physiology

196

194

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“…Anoxic thiosulfate or sulfur oxidation by strain HGMK1 T using nitrate as an electron acceptor distinguishes it from other members of the Persephonella-Hydrogenothermus clade (Table 1), but this characteristic is commonly observed in Aquifex pyrophilus Kol5A T (Huber et al, 1992), Hydrogenobaculum acidophilum 3H-1 T (Shima & Suzuki, 1993;Stöhr et al, 2001) and Hydrogenobacter thermophilus TK-6 T (Kawasumi et al, 1984;Suzuki et al, 2001). To our knowledge, however, anoxic hydrogen and sulfur/thiosulfate oxidation with iron (III), selenate, selenite or arsenate was described for the first time in the metabolism of strain HGMK1 T .…”

Section: Comparison With Related Genera and Speciesmentioning

confidence: 99%

Sulfurihydrogenibium subterraneum gen. nov., sp. nov., from a subsurface hot aquifer

Takai¹,

Kobayashi

Nealson

et al. 2003

International Journal of Systematic and Evolutionary Microbiology

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“…Most members of the order Aquificales are autotrophs and able to obtain energy by oxidation of molecular hydrogen and reduced sulfur compounds (29,32). To our knowledge, except for the possible Aquificales member Desulfurobacterium thermolithotrophum (19), molecular oxygen is recognized as the primary electron acceptor, although the nitrate-reducing growth of Hydrogenobacter thermophilus TK-6 has recently been reported (31).…”

mentioning

confidence: 99%

Isolation and Metabolic Characteristics of Previously Uncultured Members of the Order Aquificales in a Subsurface Gold Mine

Takai¹,

Hirayama²,

Sakihama

et al. 2002

Appl Environ Microbiol

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Culture-dependent and -independent techniques were combined to characterize the physiological properties and the ecological impacts of culture-resistant phylotypes of thermophiles within the order Aquificales from a subsurface hot aquifer of a Japanese gold mine. Thermophilic bacteria phylogenetically associated with previously uncultured phylotypes of Aquificales were successfully isolated. 16S ribosomal DNA clone analysis of the entire microbial DNA assemblage and fluorescence in situ whole-cell hybridization analysis indicated that the isolates dominated the microbial population in the subsurface aquifer. The isolates were facultatively anaerobic, hydrogen-or sulfur/thiosulfate-oxidizing, thermophilic chemolithoautotrophs utilizing molecular oxygen, nitrate, ferric iron, arsenate, selenate, and selenite as electron acceptors. Their versatile energygenerating systems may reflect the geochemical conditions of their habitat in the geothermally active subsurface gold mine.Culture-resistant phylotypes of thermophiles within the order Aquificales are prevalent in microbial mats or filamentous communities that often form in a certain temperature range (50 to 90°C) of habitats in global terrestrial hot spring environments such as Yellowstone National Park (12, 26), Iceland (29, 32), and Japan (40), in subterranean hot springs (23), and even in deep-sea hydrothermal vent systems (25,27). In some microbial communities, relatively well-identified members closely related to the genera Hydrogenobacter and Thermocrinis are dominant, whereas the predominant components of other communities are uncultivated phylotypes genetically distinct from cultured members of the Aquificales (11, 12, 25-27, 29, 32, 40). Their resistance to cultivation has prevented characterization of their physiological properties and ecological impacts on microbial communities.The Hishikari gold mine is located in Kagoshima Prefecture, Japan, approximately 20 km northwest of the active volcanoes of Mt. Kirishima. With increasing depth, the mine tunnels first penetrate the Pleistocene andesites (1.0 to 1.8 million years [Ma]) up to 200 m below the land surface (13). The andesites overlie the Shimanto-Supergroup shale and sandstone stratum (Ͼ650 Ma) dominated by geothermally heated fluid flow along subvertical fractures (13). Quartz veins form along the fractures (0.84 to 1.01 Ma), which contain extremely high concentrations of gold (50 g of Au per metric ton) (13). From the lower level of the hot aquifer zone, which is the deepest level of the gold mine at 320 m below the land surface, a number of slightly inclined drill holes equipped with valved pipes have been placed to explore undiscovered gold veins and control the aquifer level (dewatering station).In the course of the culture-independent, molecular phylogenetic survey of the microbial communities in the hot aquifer water samples in this study, it was found that ribosomal DNA (rDNA) signatures closely related to previously uncultivated phylotypes of members of the Aquificales were predominantly re...

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Nitrate respiratory metabolism in an obligately autotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6

Cited by 29 publications

References 20 publications

Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis,

Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis,

Sulfurihydrogenibium subterraneum gen. nov., sp. nov., from a subsurface hot aquifer

Isolation and Metabolic Characteristics of Previously Uncultured Members of the Order Aquificales in a Subsurface Gold Mine

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