Prokaryotic Abundance and Community Composition in a Freshwater Iron-Rich Microbial Mat at Circumneutral pH |
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Authors: | Shingo Kato Sakiko Kikuchi Teruhiko Kashiwabara Yoshio Takahashi Katsuhiko Suzuki Takashi Itoh |
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Institution: | 1. Japan Collection of Microorganisms , RIKEN BioResource Center , Wako , Saitama , Japan;2. Department of Molecular Biology , Tokyo University of Pharmacy and Life Science , Hachioji , Tokyo , Japan;3. Department of Earth and Planetary Systems Science, Graduate School of Science , Hiroshima University, Higashi-Hiroshima , Hiroshima , Japan;4. Department of Earth and Planetary Systems Science, Graduate School of Science , Hiroshima University, Higashi-Hiroshima , Hiroshima , Japan;5. Institute for Research on Earth Evolution (IFREE) , Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , Yokosuka , Kanagawa , Japan;6. Institute for Research on Earth Evolution (IFREE) , Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , Yokosuka , Kanagawa , Japan;7. Precambrian Ecosystem Laboratory (PEL) , Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , Yokosuka , Kanagawa , Japan;8. Japan Collection of Microorganisms , RIKEN BioResource Center , Wako , Saitama , Japan |
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Abstract: | The abundance, diversity and composition of bacterial and archaeal communities in a freshwater iron-rich microbial mat were investigated using culture-dependent and culture-independent methods. The sampling site is a mixing zone where ferrous-iron-rich fluids encounter oxygen-rich environments. Quantitative PCR analysis shows that Bacteria dominated the mat community (>99% of the total cell numbers). Phylotypes related to iron-oxidizers in Gallionellaceae, methano/methylotrophs in Methylophilaceae and Methylococcaceae, sulfide-oxidizers in Sulfuricurvum and an uncultured clone group, called Terrestrial group I or the 1068 group, in the Epsilonproteobacteria were detected in the clone library from the original sample and/or the enrichment cultures. This result suggests that these members may play a role in Fe, S and C cycling in the mixing zone. Although Archaea were minor constituents numerically, phylogenetic analysis indicates that unique and diverse yet-uncultivated Archaea are present in the iron-rich mat. The phylotypes of these yet-uncultivated Archaea belong to environmental clone groups that have been recovered from other mixing zones in terrestrial and marine environments, and some of our phylotypes have significantly low similarity (80% or lower) with the archaeal clones reported previously. Our results provide further insights into the bacterial and archaeal communities in a microaerobic iron-rich freshwater environment in mixing zones. |
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Keywords: | iron-oxidizing bacteria yet-uncultivated Archaea freshwater mixing zone iron-rich microbial mat |
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