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Journal Articles

Ecological and genomic profiling of anaerobic methane-oxidizing archaea in a deep granitic environment

Ino, Kohei*; Hernsdorf, A. W.*; Konno, Yuta*; Kozuka, Mariko*; Yanagawa, Katsunori*; Kato, Shingo*; Sunamura, Michinari*; Hirota, Akinari*; Togo, Yoko*; Ito, Kazumasa*; et al.

ISME Journal, 12(1), p.31 - 47, 2018/01

 Times Cited Count:30 Percentile:93.55(Ecology)

In this study, we found the dominance ofanaerobic methane-oxidizing archaea in groundwater enriched in sulfate and methane from a 300-m deep underground borehole in granitic rock.

Journal Articles

Age and speciation of iodine in groundwater and mudstones of the Horonobe area, Hokkaido, Japan; Implications for the origin and migration of iodine during basin evolution

Togo, Yoko*; Takahashi, Yoshio*; Amano, Yuki; Matsuzaki, Hiroyuki*; Suzuki, Yohei*; Terada, Yasuko*; Muramatsu, Yasuyuki*; Ito, Kazumasa*; Iwatsuki, Teruki

Geochimica et Cosmochimica Acta, 191, p.165 - 186, 2016/10

 Times Cited Count:13 Percentile:60.45(Geochemistry & Geophysics)

Iodine distribution, speciation, and isotope ratio ($$^{129}$$I/$$^{127}$$I) in both rock and groundwater phases were determined to investigate long-term migration of iodine in diatomaceous and siliceous shale. It was suggested that I$$^{-}$$ is released to the ground water during the progress of the maturation of organic matter. Dissociated I$$^{-}$$ could move toward the surface because of the upward water flow driven by the compaction during burial diagenetic process. Thus, iodine rich brine is created by integration of iodine released from underlying formations. Because of low affinity of I$$^{-}$$ to solid phase, released I$$^{-}$$ remains in solution phase, and the concentration of the iodine in the solution has been possibly increasing during sedimentation history.

Journal Articles

Deep microbial life in high-quality granitic groundwater from geochemically and geographically distinct underground boreholes

Ino, Kohei*; Konno, Yuta*; Kozuka, Mariko*; Hirota, Akinari*; Togo, Yoko*; Fukuda, Akari*; Komatsu, Daisuke*; Tsunogai, Urumu*; Tanabe, Akifumi*; Yamamoto, Satoshi*; et al.

Environmental Microbiology Reports (Internet), 8(2), p.285 - 294, 2016/04

 Times Cited Count:18 Percentile:67.66(Environmental Sciences)

To understand the subsurface biosphere, borehole investigation was conducted for 300-m deep granitic rocks at the Mizunami underground research laboratory, Japan. The initial biomass was the highest with the flourish of aerobic H$$_{2}$$-oxidizing Hydrogenophaga spp., whereas an uncultivated lineage of the phylum Nitrospirae became predominant after three years with decreasing biomass. The common occurrence of many species of Nitrospirae and Chlorobi phyla at the geographically distinct sites and the exclusive detection of their phylogenetically related environmental sequences from deep groundwaters and terrestrial hot springs, suggest that these bacteria are indigenous and potentially adapted to the deep terrestrial subsurface.

Journal Articles

Biogeochemical signals from deep microbial life in terrestrial crust

Suzuki, Yohei*; Konno, Yuta*; Fukuda, Akari*; Komatsu, Daisuke*; Hirota, Akinari*; Watanabe, Katsuaki*; Togo, Yoko*; Morikawa, Noritoshi*; Hagiwara, Hiroki; Aosai, Daisuke*; et al.

PLOS ONE (Internet), 9(12), p.e113063_1 - e113063_20, 2014/12

 Times Cited Count:9 Percentile:36.08(Multidisciplinary Sciences)

We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep groundwater of meteoric origin was collected from underground boreholes drilled into the Cretaceous Toki granite, central Japan. A large sulfur isotopic fractionation of 20-60 permil diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation ($$<$$ 30 permil) is not indicative of methanogenesis. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low energy fluxes.

Oral presentation

Behavior of iodine in the soil-water and rock-water systems

Togo, Yoko*; Takahashi, Yoshio*; Amano, Yuki; Matsuzaki, Hiroyuki*; Muramatsu, Yasuyuki*; Iwatsuki, Teruki

no journal, , 

To understand behavior of iodine in shallow and deep underground is essential because radioactive wastes, which contain high levels of radioiodine, are planned to be stored in underground nuclear-waste repository. We determined iodine distribution, speciation, and isotope ratio ($$^{129}$$I/$$^{127}$$I), to investigate long-term migration of iodine in diatomaceous and siliceous shales, using core and groundwater samples collected at JAEA Horonobe underground research center. Iodine exists as I- in groundwater, while that in shales is a mixture of organic and inorganic I.

Oral presentation

Interaction between trace elements and colloids in groundwater using SEC-ICP-MS

Togo, Yoko*; Suzuki, Yohei*; Fukuda, Akari; Mizuno, Takashi; Ito, Kazumasa*

no journal, , 

no abstracts in English

Oral presentation

Long-term migration of iodine in sedimentary rocks based on iodine speciation and $$^{129}$$I/$$^{127}$$I ratios

Togo, Yoko*; Takahashi, Yoshio*; Amano, Yuki; Matsuzaki, Hiroyuki*; Suzuki, Yohei*; Muramatsu, Yasuyuki*; Iwatsuki, Teruki

no journal, , 

Radioactive iodine ($$^{129}$$I) is one of the available indexes of long-term migration of groundwater solutes, because of its long half-life (15.7 million years) and low sorption characteristics. All rock and groundwater samples were collected at Horonobe underground research center. Species of iodine in groundwater was mainly I$$^{-}$$. $$^{129}$$I/$$^{127}$$I isotope ratios in groundwater were lower than that in rocks and almost constant at various depths, demonstrating that iodine in groundwater was released from deeper than co-existing rocks.

Oral presentation

JAEA/AIST collaborative research project; Development and evaluation of investigation methodology to quantity microbial influence on the deep hydrogeochemical properties

Fukuda, Akari; Iwatsuki, Teruki; Shingu, Shinya; Omori, Kazuaki; Hagiwara, Hiroki; Ito, Kazumasa*; Togo, Yoko*; Suzuki, Yohei*

no journal, , 

no abstracts in English

Oral presentation

Collaboration research of JAEA and AIST; Evaluation methods on microbial activity and geochemical condition

Ito, Kazumasa*; Togo, Yoko*; Hirota, Akinari*; Suzuki, Yohei*; Fukuda, Akari*; Omori, Kazuaki; Hasegawa, Takashi; Iwatsuki, Teruki

no journal, , 

Microbial metabolism and the chemical buffer capacity in deep groundwater were estimated at Mizunami underground research laboratory. The results show that sulfate reducing bacteria uses hydrogen gas. The sulfate consumption rate is important index to infer the redox buffer capacity in deep underground.

Oral presentation

Microbial sulfate reduction and sulfur isotope fractionations in deep groundwater at Mizunami Underground Research Laboratory

Hirota, Akinari*; Togo, Yoko*; Ito, Kazumasa*; Suzuki, Yohei*; Fukuda, Akari*; Konno, Yuta*; Tsunogai, Urumu*; Komatsu, Daiyu*; Nagao, Seiya*; Iwatsuki, Teruki

no journal, , 

Isotopic compositions of sulfate, sulfide ions were measured in deep groundwater of Mizunami URL to estimate microbial activity. The results show that relatively large isotopic fractionation between sulfate and sulfide by microbial reduction.

Oral presentation

Microbial sulfate reduction and CO$$_{2}$$ reduction at deep granitic aquifer by anaerobic and high pressure culture experiment

Hirota, Akinari*; Togo, Yoko*; Fukuda, Akari*; Ito, Kazumasa*; Suzuki, Yohei*; Tsunogai, Urumu*; Komatsu, Daiyu*; Iwatsuki, Teruki

no journal, , 

Microbial activity in deep groundwater at Mizunami URL was estimated based on isotopic composition. The result shows that sulfate reduction activity is higher at low-H$$_{2}$$ gas condition.

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