Characterization of metabolically active bacterial populations in subseafloor Nankai Trough sediments above, within, and below the sulfate-methane transition zone

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doi: 10.3389/fmicb.2012.00113
Author(s): Mills, Heath J.; Reese, Brandi Kiel; Shepard, Alicia K.; Riedinger, Natascha; Dowd, Scot E.; Morono, Yuki; Inagaki, Fumio
Author Affiliation(s): Primary:
Texas A&M University, Department of Oceanography, College Station, TX, United States
Other:
University of Southern California, United States
University of California-Riverside, United States
Medical Biofilm Research Institute, United States
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: Frontiers in Microbiology
Source: Frontiers in Microbiology, Vol.3(Article 113), p.1-12. Publisher: Frontiers Research Foundation, Lausanne, Switzerland. ISSN: 1664-302X
Note: In English. 65 refs.; illus.
Summary: A remarkable number of microbial cells have been enumerated within subseafloor sediments, suggesting a biological impact on geochemical processes in the subseafloor habitat. However, the metabolically active fraction of these populations is largely uncharacterized. In this study, an RNA-based molecular approach was used to determine the diversity and community structure of metabolically active bacterial populations in the upper sedimentary formation of the Nankai Trough seismogenic zone. Samples used in this study were collected from the slope apron sediment overlying the accretionary prism at Site C0004 during the Integrated Ocean Drilling Program Expedition 316. The sediments represented microbial habitats above, within, and below the sulfate-methane transition zone (SMTZ), which was observed approximately 20 m below the seafloor (mbsf). Small subunit ribosomal RNA were extracted, quantified, amplified, and sequenced using high-throughput 454 pyrosequencing, indicating the occurrence of metabolically active bacterial populations to a depth of 57 mbsf. Transcript abundance and bacterial diversity decreased with increasing depth. The two communities below the SMTZ were similar at the phylum level, however only a 24% overlap was observed at the genus level. Active bacterial community composition was not confined to geochemically predicted redox stratification despite the deepest sample being more than 50 m below the oxic/anoxic interface. Genus-level classification suggested that the metabolically active subseafloor bacterial populations had similarities to previously cultured organisms. This allowed predictions of physiological potential, expanding understanding of the subseafloor microbial ecosystem. Unique community structures suggest very diverse active populations compared to previous DNA-based diversity estimates, providing more support for enhancing community characterizations using more advanced sequencing techniques.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 22 Environmental Geology; Asia; Bacteria; Biochemistry; Biosphere; Communities; Cores; Depth; Ecology; Far East; Genetics; IODP Site C0004; Integrated Ocean Drilling Program; Japan; Marine sediments; Metabolism; Microorganisms; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Nucleic acids; Pacific Ocean; Phylogeny; Pore water; RNA; Sediments; Species diversity; West Pacific
Coordinates: N331300 N331300 E1364300 E1364300
Record ID: 2013048189
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