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Rattray JE, Chakraborty A, Li C, Elizondo G, John N, Wong M, Radović JR, Oldenburg TBP, Hubert CRJ. Sensitive quantification of dipicolinic acid from bacterial endospores in soils and sediments. Environ Microbiol 2020; 23:1397-1406. [PMID: 33264453 PMCID: PMC8048543 DOI: 10.1111/1462-2920.15343] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 11/30/2020] [Indexed: 11/27/2022]
Abstract
Endospore-forming bacteria make up an important and numerically significant component of microbial communities in a range of settings including soils, industry, hospitals and marine sediments extending into the deep subsurface. Bacterial endospores are non-reproductive structures that protect DNA and improve cell survival during periods unfavourable for bacterial growth. An important determinant of endospores withstanding extreme environmental conditions is 2,6-pyridine dicarboxylic acid (i.e. dipicolinic acid, or DPA), which contributes heat resistance. This study presents an improved HPLC-fluorescence method for DPA quantification using a single 10-min run with pre-column Tb3+ chelation. Relative to existing DPA quantification methods, specific improvements pertain to sensitivity, detection limit and range, as well as the development of new free DPA and spore-specific DPA proxies. The method distinguishes DPA from intact and recently germinated spores, enabling responses to germinants in natural samples or experiments to be assessed in a new way. DPA-based endospore quantification depends on accurate spore-specific DPA contents, in particular, thermophilic spores are shown to have a higher DPA content, meaning that marine sediments with plentiful thermophilic spores may require spore number estimates to be revisited. This method has a wide range of potential applications for more accurately quantifying bacterial endospores in diverse environmental samples.
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Affiliation(s)
- Jayne E Rattray
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
| | - Anirban Chakraborty
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
| | - Carmen Li
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
| | - Gretta Elizondo
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
| | - Nisha John
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
| | - Michelle Wong
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
| | - Jagoš R Radović
- Department of Geoscience, University of Calgary, Calgary, T2N 1N4, Canada
| | | | - Casey R J Hubert
- Department of Biological Sciences, University of Calgary, Calgary, T2N 1N4, Canada
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2
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Heuer VB, Inagaki F, Morono Y, Kubo Y, Spivack AJ, Viehweger B, Treude T, Beulig F, Schubotz F, Tonai S, Bowden SA, Cramm M, Henkel S, Hirose T, Homola K, Hoshino T, Ijiri A, Imachi H, Kamiya N, Kaneko M, Lagostina L, Manners H, McClelland HL, Metcalfe K, Okutsu N, Pan D, Raudsepp MJ, Sauvage J, Tsang MY, Wang DT, Whitaker E, Yamamoto Y, Yang K, Maeda L, Adhikari RR, Glombitza C, Hamada Y, Kallmeyer J, Wendt J, Wörmer L, Yamada Y, Kinoshita M, Hinrichs KU. Temperature limits to deep subseafloor life in the Nankai Trough subduction zone. Science 2020; 370:1230-1234. [PMID: 33273103 DOI: 10.1126/science.abd7934] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 10/13/2020] [Indexed: 02/06/2023]
Abstract
Microorganisms in marine subsurface sediments substantially contribute to global biomass. Sediments warmer than 40°C account for roughly half the marine sediment volume, but the processes mediated by microbial populations in these hard-to-access environments are poorly understood. We investigated microbial life in up to 1.2-kilometer-deep and up to 120°C hot sediments in the Nankai Trough subduction zone. Above 45°C, concentrations of vegetative cells drop two orders of magnitude and endospores become more than 6000 times more abundant than vegetative cells. Methane is biologically produced and oxidized until sediments reach 80° to 85°C. In 100° to 120°C sediments, isotopic evidence and increased cell concentrations demonstrate the activity of acetate-degrading hyperthermophiles. Above 45°C, populated zones alternate with zones up to 192 meters thick where microbes were undetectable.
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Affiliation(s)
- Verena B Heuer
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
| | - Fumio Inagaki
- Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan.,Kochi Institute for Core Sample Research, JAMSTEC, Kochi, Japan
| | - Yuki Morono
- Kochi Institute for Core Sample Research, JAMSTEC, Kochi, Japan
| | - Yusuke Kubo
- Center for Deep Earth Exploration (CDEX), JAMSTEC, Yokohama, Japan
| | - Arthur J Spivack
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Bernhard Viehweger
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
| | - Tina Treude
- Department of Earth, Planetary, and Space Sciences, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
| | - Felix Beulig
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Florence Schubotz
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
| | - Satoshi Tonai
- Faculty of Science and Technology, Kochi University, Kochi, Japan
| | - Stephen A Bowden
- Department of Geology and Petroleum Geology, School of Geosciences, University of Aberdeen, Aberdeen, UK
| | - Margaret Cramm
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Susann Henkel
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Takehiro Hirose
- Kochi Institute for Core Sample Research, JAMSTEC, Kochi, Japan
| | - Kira Homola
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | | | - Akira Ijiri
- Kochi Institute for Core Sample Research, JAMSTEC, Kochi, Japan
| | - Hiroyuki Imachi
- Institute for Extra-cutting-edge Science and Technology Avantgarde Research, JAMSTEC, Yokosuka, Japan
| | - Nana Kamiya
- Graduate School of Integrated Basic Sciences, Nihon University, Tokyo, Japan
| | - Masanori Kaneko
- Geomicrobiology Research Group, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Lorenzo Lagostina
- Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
| | - Hayley Manners
- School of Geography, Earth and Environmental Sciences, Faculty of Science and Engineering, Plymouth University, Plymouth, UK
| | - Harry-Luke McClelland
- Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA
| | - Kyle Metcalfe
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Natsumi Okutsu
- Atmosphere and Ocean Research Institute, University of Tokyo, Tokyo, Japan
| | - Donald Pan
- Department of Subsurface Geobiological Analysis and Research, JAMSTEC, Yokosuka, Japan
| | - Maija J Raudsepp
- School of Earth Sciences, University of Queensland, St. Lucia, QLD, Australia
| | - Justine Sauvage
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Man-Yin Tsang
- Department of Earth Sciences, University of Toronto, Toronto, ON, Canada
| | - David T Wang
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Emily Whitaker
- Department of Oceanography, Texas A&M University, College Station, TX, USA
| | - Yuzuru Yamamoto
- Department of Mathematical Science and Advanced Technology, JAMSTEC, Yokosuka, Japan
| | - Kiho Yang
- Department of Earth System Sciences, Yonsei University, Seoul, Republic of Korea
| | - Lena Maeda
- Center for Deep Earth Exploration (CDEX), JAMSTEC, Yokohama, Japan
| | - Rishi R Adhikari
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
| | - Clemens Glombitza
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zürich, Switzerland
| | - Yohei Hamada
- Kochi Institute for Core Sample Research, JAMSTEC, Kochi, Japan
| | - Jens Kallmeyer
- GFZ German Research Centre for Geosciences, Potsdam, Germany
| | - Jenny Wendt
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
| | - Lars Wörmer
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
| | - Yasuhiro Yamada
- Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan
| | | | - Kai-Uwe Hinrichs
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany.
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Rambo IM, Marsh A, Biddle JF. Cytosine Methylation Within Marine Sediment Microbial Communities: Potential Epigenetic Adaptation to the Environment. Front Microbiol 2019; 10:1291. [PMID: 31244806 PMCID: PMC6579885 DOI: 10.3389/fmicb.2019.01291] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 05/23/2019] [Indexed: 02/01/2023] Open
Abstract
Marine sediments harbor a vast amount of Earth's microbial biomass, yet little is understood regarding how cells subsist in this low-energy, presumably slow-growth environment. Cells in marine sediments may require additional methods for genetic regulation, such as epigenetic modification via DNA methylation. We investigated this potential phenomenon within a shallow estuary sediment core spanning 100 years of age. Here, we provide evidence of dynamic community m5-cytosine methylation within estuarine sediment metagenomes. The methylation states of individual CpG sites were reconstructed and quantified across three depths within the sediment core. A total of 6,254 CpG sites were aligned for direct comparison of methylation states between samples, and 4,235 of these sites mapped to taxa and genes. Our results demonstrate the presence of differential methylation within environmental CpG sites across an age gradient of sediment. We show that epigenetic modification can be detected via Illumina sequencing within complex environmental communities. The change in methylation state of environmentally relevant genes across depths may indicate a dynamic role of DNA methylation in regulation of biogeochemical processes.
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Affiliation(s)
| | | | - Jennifer F. Biddle
- School of Marine Science and Policy, University of Delaware, Lewes, DE, United States
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Cupit C, Lomstein BA, Kjeldsen KU. Contrasting community composition of endospores and vegetative Firmicutes in a marine sediment suggests both endogenous and exogenous sources of endospore accumulation. ENVIRONMENTAL MICROBIOLOGY REPORTS 2019; 11:352-360. [PMID: 30043505 DOI: 10.1111/1758-2229.12679] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 07/09/2018] [Accepted: 07/12/2018] [Indexed: 06/08/2023]
Abstract
Bacterial endospores are highly abundant in marine sediments, but their taxonomic identity and ecology is largely unknown. We selectively extracted DNA from endospores and vegetative cells and sequenced 16S rRNA genes to characterize the composition of the endospore and vegetative Firmicutes communities in the sediment and water column of Aarhus Bay (Denmark). The endospore community in the sediment was dominated by the families Bacillaceae, Lachnospiraceae, Clostridiaceae and Ruminoccocaceae. These families were also represented in the vegetative community in the sediment and the endospore community in the water column. OTUs of high relative abundance in the endospore community were also represented in the vegetative Firmicutes community. Other OTUs were exclusively found in the endospore communities. This suggests that endospores accumulate in marine sediments due to passive deposition from the water column and sporulation of vegetative cells in the sediment. Some OTUs were detected in the endospore community of the water column and the vegetative community the sediment indicating that endospores deposited from the water column may germinate upon burial/deposition in the sediment. We provide novel insight into the composition of endospore communities in marine sediments and highlight their role in microbial dispersal and as a seed bank in subsurface sediments.
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Affiliation(s)
- Carina Cupit
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Bente Aagaard Lomstein
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Kasper Urup Kjeldsen
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
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5
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Wörmer L, Hoshino T, Bowles MW, Viehweger B, Adhikari RR, Xiao N, Uramoto GI, Könneke M, Lazar CS, Morono Y, Inagaki F, Hinrichs KU. Microbial dormancy in the marine subsurface: Global endospore abundance and response to burial. SCIENCE ADVANCES 2019; 5:eaav1024. [PMID: 30801015 PMCID: PMC6382399 DOI: 10.1126/sciadv.aav1024] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 01/11/2019] [Indexed: 05/19/2023]
Abstract
Marine sediments host an unexpectedly large microbial biosphere, suggesting unique microbial mechanisms for surviving burial and slow metabolic turnover. Although dormancy is generally considered an important survival strategy, its specific role in subsurface sediments remains unclear. We quantified dormant bacterial endospores in 331 marine sediment samples from diverse depositional types and geographical origins. The abundance of endospores relative to vegetative cells increased with burial depth and endospores became dominant below 25 m, with an estimated population of 2.5 × 1028 to 1.9 × 1029 endospores in the uppermost kilometer of sediment and a corresponding biomass carbon of 4.6 to 35 Pg surpassing that of vegetative cells. Our data further identify distinct endospore subgroups with divergent resistance to burial and aging. Endospores may shape the deep biosphere by providing a core population for colonization of new habitats and/or through low-frequency germination to sustain slow growth in this environment.
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Affiliation(s)
- Lars Wörmer
- MARUM—Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany
- Corresponding author.
| | - Tatsuhiko Hoshino
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
| | | | - Bernhard Viehweger
- MARUM—Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany
| | - Rishi R. Adhikari
- MARUM—Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany
| | - Nan Xiao
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
| | - Go-ichiro Uramoto
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
- Center for Advanced Marine Core Research, Kochi University, Kochi 783-8502, Japan
| | - Martin Könneke
- MARUM—Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany
| | - Cassandre S. Lazar
- MARUM—Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany
- Department of Biological Sciences, Université du Québec à Montréal (UQAM), Montreal, Quebec H3C 3P8, Canada
| | - Yuki Morono
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
| | - Fumio Inagaki
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
- Research and Development Center for Ocean Drilling Science, JAMSTEC, Yokohama 236-0001, Japan
| | - Kai-Uwe Hinrichs
- MARUM—Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, 28359 Bremen, Germany
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6
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Fang J, Kato C, Runko GM, Nogi Y, Hori T, Li J, Morono Y, Inagaki F. Predominance of Viable Spore-Forming Piezophilic Bacteria in High-Pressure Enrichment Cultures from ~1.5 to 2.4 km-Deep Coal-Bearing Sediments below the Ocean Floor. Front Microbiol 2017; 8:137. [PMID: 28220112 PMCID: PMC5292414 DOI: 10.3389/fmicb.2017.00137] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 01/19/2017] [Indexed: 11/13/2022] Open
Abstract
Phylogenetically diverse microorganisms have been observed in marine subsurface sediments down to ~2.5 km below the seafloor (kmbsf). However, very little is known about the pressure-adapted and/or pressure-loving microorganisms, the so called piezophiles, in the deep subseafloor biosphere, despite that pressure directly affects microbial physiology, metabolism, and biogeochemical processes of carbon and other elements in situ. In this study, we studied taxonomic compositions of microbial communities in high-pressure incubated sediment, obtained during the Integrated Ocean Drilling Program (IODP) Expedition 337 off the Shimokita Peninsula, Japan. Analysis of 16S rRNA gene-tagged sequences showed that members of spore-forming bacteria within Firmicutes and Actinobacteria were predominantly detected in all enrichment cultures from ~1.5 to 2.4 km-deep sediment samples, followed by members of Proteobacteria, Acidobacteria, and Bacteroidetes according to the sequence frequency. To further study the physiology of the deep subseafloor sedimentary piezophilic bacteria, we isolated and characterized two bacterial strains, 19R1-5 and 29R7-12, from 1.9 and 2.4 km-deep sediment samples, respectively. The isolates were both low G+C content, gram-positive, endospore-forming and facultative anaerobic piezophilic bacteria, closely related to Virgibacillus pantothenticus and Bacillus subtilis within the phylum Firmicutes, respectively. The optimal pressure and temperature conditions for growth were 20 MPa and 42°C for strain 19R1-5, and 10 MPa and 43°C for strain 29R7-12. Bacterial (endo)spores were observed in both the enrichment and pure cultures examined, suggesting that these piezophilic members were derived from microbial communities buried in the ~20 million-year-old coal-bearing sediments after the long-term survival as spores and that the deep biosphere may host more abundant gram-positive spore-forming bacteria and their spores than hitherto recognized.
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Affiliation(s)
- Jiasong Fang
- Hadal Science and Technology Research Center, Shanghai Ocean UniversityShanghai, China; Department of Natural Sciences, Hawaii Pacific University, HonoluluHI, USA
| | - Chiaki Kato
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology Yokosuka, Japan
| | - Gabriella M Runko
- Department of Natural Sciences, Hawaii Pacific University, Honolulu HI, USA
| | - Yuichi Nogi
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology Yokosuka, Japan
| | - Tomoyuki Hori
- Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Ibaraki, Japan
| | - Jiangtao Li
- State Key Laboratory of Marine Geology, Tongji University Shanghai, China
| | - Yuki Morono
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology Kochi, Japan
| | - Fumio Inagaki
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and TechnologyKochi, Japan; Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and TechnologyYokohama, Japan; Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and TechnologyYokosuka, Japan
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7
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Nunoura T, Takaki Y, Shimamura S, Kakuta J, Kazama H, Hirai M, Masui N, Tomaru H, Morono Y, Imachi H, Inagaki F, Takai K. Variance and potential niche separation of microbial communities in subseafloor sediments off Shimokita Peninsula, Japan. Environ Microbiol 2015; 18:1889-906. [PMID: 26486095 DOI: 10.1111/1462-2920.13096] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/21/2015] [Accepted: 10/05/2015] [Indexed: 01/23/2023]
Abstract
Subseafloor pelagic sediments with high concentrations of organic matter form habitats for diverse microorganisms. Here, we determined depth profiles of genes for SSU rRNA, mcrA, dsrA and amoA from just beneath the seafloor to 363.3 m below the seafloor (mbsf) using core samples obtained from the forearc basin off the Shimokita Peninsula. The molecular profiles were combined with data on lithostratigraphy, depositional age, sedimentation rate and pore-water chemistry. The SSU rRNA gene tag structure and diversity changed at around the sulfate-methane transition zone (SMTZ), whereas the profiles varied further with depth below the SMTZ, probably in connection with the variation in pore-water chemistry. The depth profiles of diversity and abundance of dsrA, a key gene for sulfate reduction, suggested the possible niche separations of sulfate-reducing populations, even below the SMTZ. The diversity and abundance patterns of mcrA, a key gene for methanogenesis/anaerobic methanotrophy, suggested a stratified distribution and separation of anaerobic methanotrophy and hydrogenotrophic or methylotrophic methanogensis below the SMTZ. This study provides novel insights into the relationships between the composition and function of microbial communities and the chemical environment in the nutrient-rich continental margin subseafloor sediments, which may result in niche separation and variability in subseafloor microbial populations.
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Affiliation(s)
- Takuro Nunoura
- Marine Functional Biology Group, Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Yoshihiro Takaki
- Marine Functional Biology Group, Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.,Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Shigeru Shimamura
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Jungo Kakuta
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Hiromi Kazama
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Miho Hirai
- Marine Functional Biology Group, Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Noriaki Masui
- Geomicrobiology Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi, Japan
| | - Hitoshi Tomaru
- Department of Earth Sciences, Chiba University, Chiba, Inageku, Japan
| | - Yuki Morono
- Geomicrobiology Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi, Japan
| | - Hiroyuki Imachi
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Fumio Inagaki
- Geomicrobiology Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi, Japan
| | - Ken Takai
- Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
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