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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

The Role of low-temperature organic matter diagenesis in carbonate precipitation within a marine deposit

Miyakawa, Kazuya; Ishii, Eiichi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*

Applied Geochemistry, 76, p.218 - 231, 2017/01

 Times Cited Count:8 Percentile:49.44(Geochemistry & Geophysics)

no abstracts in English

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.

Journal Articles

Occurrence and potential activity of denitrifiers and methanogens in groundwater at 140 m depth in Pliocene diatomaceous mudstone of northern Japan

Katsuyama, Chie*; Nashimoto, Hiroaki*; Nagaosa, Kazuyo*; Ishibashi, Tomotaka*; Furuta, Kazuki*; Kinoshita, Takeshi*; Yoshikawa, Hideki; Aoki, Kazuhiro; Asano, Takahiro*; Sasaki, Yoshito; et al.

FEMS Microbiology Ecology, 86(3), p.532 - 543, 2013/12

 Times Cited Count:8 Percentile:26.35(Microbiology)

Anaerobic microbial activity has a major influence on the subsurface environment, and should be considered in subsurface activities including the construction of radioactive waste repositories. We investigated denitrification and methanogenesis in anoxic groundwater from 140 m depth in two boreholes, where the redox potential fluctuated. The average maximum potential denitrification rates, measured under anaerobic conditions in the two boreholes using an $$^{15}$$N tracer. Methanogenesis candidates were detected by 16S rRNA gene analysis. Although the stable isotope signatures suggested that some of the dissolved methane was of biogenic origin, no potential for methane production was evident during the incubations. The groundwater at 140 m depth did not contain oxygen, had an Eh ranging from -144 to 6.8 mV, and was found to be a potential field for denitrification.

Journal Articles

Geomicrobiological properties of ultra-deep granitic groundwater from the Mizunami Underground Research Laboratory (MIU), Central Japan

Fukuda, Akari*; Hagiwara, Hiroki; Ishimura, Toyoho*; Kozuka, Mariko*; Ioka, Seiichiro*; Amano, Yuki; Tsunogai, Urumu*; Suzuki, Yohei*; Mizuno, Takashi

Microbial Ecology, 60(1), p.214 - 225, 2010/05

 Times Cited Count:23 Percentile:62.17(Ecology)

To better understand the geochemical and microbiological relationships, we characterized granitic groundwater collected from a 1,148 to 1,169 -m deep borehole interval at the Mizunami Underground Research Laboratory site, Japan, in 2005 and 2008. Geochemical analyses of the groundwater samples indicated that major electron acceptors, such as NO$$_{3}$$$$^{-}$$ and SO$$_{4}$$$$^{2-}$$, were not abundant, while dissolved organic carbon (not including organic acids), CH$$_{4}$$ and H$$_{2}$$ were moderately rich. The most common phylotypes were both related to ${it Thauera}$ spp., the cultivated members of which can utilize minor electron donors, such as aromatic and aliphatic hydrocarbons. Geomicrobiological results suggest that deep granitic groundwater has been stably colonized by ${it Thauera}$ spp. probably owing to the limitation of O$$_{2}$$, NO$$_{3}$$$$^{-}$$ and organic acids.

Oral presentation

Collaborative project of JAEA/AIST on hydrochemical study at MIU construction site, 2; Biogeochemical study

Fukuda, Akari*; Hagiwara, Hiroki; Ishimura, Toyoho*; Kozuka, Mariko*; Ito, Kazumasa*; Tsunogai, Urumu*; Suzuki, Yohei*; Mizuno, Takashi

no journal, , 

JAEA and AIST have been conducting collaborative work on hydrochemical study at MIU construction site. The aim of this collaborative study is to establish the methodology for investigation, analysis and evaluation of colloid/organics/microbes study. This paper reports the biogeochemical study. As the result, it is suggested that groundwater taken from deeper part (1150m depth) is relatively oxidized.

Oral presentation

Unveil the depth of microbial methane production in a sedimentary rock subsurface system

Kato, Kenji*; Nagaosa, Kazuyo*; Tsunogai, Urumu*; Asano, Takahiro; Sasaki, Yoshito; Yoshikawa, Hideki

no journal, , 

no abstracts in English

Oral presentation

BIO-NANO-GEO Science in deep underground; Approaches at Mizunami Underground Research Laboratory

Suzuki, Yohei*; Fukuda, Akari*; Kozuka, Mariko*; Ishimura, Toyoho*; Tsunogai, Urumu*; Hagiwara, Hiroki; Mizuno, Takashi

no journal, , 

no abstracts in English

Oral presentation

Hydrogen and carbon isotope geochemistry of freshwater aquifers at the Mizunami Underground Research Laboratory; Implications for ongoing biogeochemical processes in granitic rocks

Konno, Yuta*; Fukuda, Akari; Kozuka, Mariko*; Komatsu, Daisuke*; Tsunogai, Urumu*; Aosai, Daisuke; Mizuno, Takashi; Suzuki, Yohei*

no journal, , 

Our knowledge of biogeochemical processes mediated in those associated with freshwater should be integrated. We collected the groundwater samples from 200 m to 1150 m depths below ground level at Mizunami Underground Research Laboratory located in central Japan. We measured the concentration and both hydrogen and carbon isotopic compositions of dissolved methane, total inorganic carbon (TIC) and molecular hydrogen. The origin of methane could be speculated to be not biogenic CO$$_{2}$$ reduction or acetate fermentation but thermogenic or abiogenic. In contrast, C1/C2+C3 ratios supported biogenic methane production. The 300 m deep samples were enriched in hydrogen and acetate and depleted in sulfate, which is characteristic of acetogenesis. From these results, it is suggested that the production of acetate rather than methane could be dominant biogeochemical processes in the reducing portions of freshwater aquifers in granitic rocks.

Oral presentation

Possible depths for methanogenesis in deep subsurface environment of sedimentary geological setting

Nashimoto, Hiroaki*; Nagaosa, Kazuyo*; Katsuyama, Chie*; Tsunogai, Urumu*; Yoshikawa, Hideki; Asano, Takahiro; Sasaki, Yoshito; Aoki, Kazuhiro; Kato, Kenji*

no journal, , 

no abstracts in English

Oral presentation

Shifts in microbial sulfate reduction to CO$$_{2}$$ reduction depending on groundwater flow characteristics in deep granitic aquifers

Konno, Yuta*; Komatsu, Daisuke*; Nishimura, Shusaku*; Fukuda, Akari; Aosai, Daisuke; Mizuno, Takashi; Nagao, Seiya*; Tsunogai, Urumu*; Suzuki, Yohei*

no journal, , 

no abstracts in English

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.

Oral presentation

Generation processes of methane and carbon dioxide at deep underground of Horonobe area, Hokkaido, Japan

Miyakawa, Kazuya; Mizuno, Takashi; Hirota, Akinari*; Komatsu, Daisuke*; Tsunogai, Urumu*

no journal, , 

no abstracts in English

Oral presentation

Relative burial-depth-profiles of carbon isotope ratios of methane and carbon dioxide preserved for up to 1 million years

Miyakawa, Kazuya; Mizuno, Takashi; Ishii, Eiichi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*

no journal, , 

no abstracts in English

Oral presentation

Microbial CO$$_{2}$$ reduction continuing for millions years in Neogene mudstone resulting in extreme $$^{13}$$C-enrichment

Miyakawa, Kazuya; Ishii, Eiichi; Mizuno, Takashi; Hirota, Akinari*; Komatsu, Daisuke*; Ikeya, Kosuke*; Tsunogai, Urumu*

no journal, , 

no abstracts in English

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