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Marine Ecology Progress Series

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MEPS 245:61-67 (2002)  -  doi:10.3354/meps245061

Phylogenetic characterization and biomass estimation of bacterial endosymbionts associated with invertebrates dwelling in chemosynthetic communities of hydrothermal vent and cold seep fields

Hiroyuki Yamamoto1,*, Katsunori Fujikura2, Akira Hiraishi3, Kenji Kato4, Yonosuke Maki5

1Department of Microbiology, St. Marianna University School of Medicine, Sugao 2-16-1, Miyamae, Kawasaki, Kanagawa 216-8511, Japan
2Marine Ecosystems Research Department, Japan Marine Science and Technology Center, Natushima 2-15, Yokosuka, Kanagawa 237-0061, Japan
3Department of Ecological Engineering, Toyohashi University of Technology, Tenpaku-cho Hibarigaoka, Toyohashi, Aichi 441-8580, Japan
4Department of Biological Sciences and Geosciences, Shizuoka University, Ootani 836, Shizuoka 422-8529, Japan
5Laboratory of Biology, Faculty of Humanities and Social Sciences, Iwate University, Ueda 3-18-34, Morioka, Iwate 020-8550, Japan

ABSTRACT: Molecular phylogenetics for endosymbiotic bacteria recovered from vestimentiferan tubeworm Lamellibrachia satsuma from Kagoshima Bay, vesicomyid clam Calyptogena laubieri from the Nankai Trough and mytilid mussel Bathymodiolus sp. from the Mariana Back-arc Basin, were examined by PCR-aided 16S rDNA cloning and sequencing, and quinone profiling. The 16SrRNA clones of the endosymbionts from the 3 organisms fall within γ -Proteobacter ia and showed distinct lines of descent specific to their respective host. The 16S rRNA gene phylogeny confirms the host-endosymbiont specificity in the co-evolutionary process. Ubiquinones with 9 isoprene units (Q-9) or Q-10 were found as the major quinones in all test tissues of the host. Larger amounts of Q-8 were detectable only in those host body parts (gill or trophosome) harboring the endosymbiotic bacteria. These observations suggest that Q-8 is the major quinone of the endosymbionts. Based on the bacterial quinone concentration, the population densities of the bacteria present were estimated to be 1010 to 1011 cells g-1 wet wt of host tissue. The quantitative determination of quinones may provide information about physiological activity of the chemosynthetic communities as well as their biomass production.

KEY WORDS: Quinone · 16S rRNA · Symbiosis · Chemosynthetic community · Mytilid mussel · Vesicomyid clam · Vestimentiferan tubeworm

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