Bacterial Endosymbioses of Gutless Tube-Dwelling Worms in Nonhydrothermal Vent Habitats |
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Authors: | Takeshi Naganuma Hosam E Elsaied Daiki Hoshii Hiroyuki Kimura |
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Institution: | (1) Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-hiroshima 739-8528, Japan;(2) Present address: Faculty of Science, Shizuoka University, Oya 836, Shizuoka 422-8529, Japan |
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Abstract: | Gutless tube-dwelling worms of pogonophorans (also known as frenulates) and vestimentiferans depend on primary production
of endosymbiotic bacteria. The endosymbionts include thiotrophs that oxidize sulfur for autotrophic production and methanotrophs
that oxidize and assimilate methane. Although most of the pogonophoran and vestimentiferan tube worms possess single thiotrophic
16S rRNA genes (16S rDNA) related to γ-proteobacteria, some pogonohorans are known to bear single methanotroph species or
even dual symbionts of thiotrophs and methanotrophs. The vestimentiferan Lamellibrachia sp. L1 shows symbiotic 16S rDNA sequences of α-, β-, γ-, and ε-proteobacteria, varying among specimens, with RuBisCO form
II gene (cbbM) sequences related to β-proteobacteria. An unidentified pogonophoran from the world’s deepest cold seep, 7326-m deep in the
Japan Trench, hosts a symbiotic thiotroph based on 16S rDNA with the RuBisCO form I gene (cbbL). In contrast, a shallow-water pogonophoran (Oligobrachia mashikoi) in coastal Japan Sea has a methanotrophic 16S rDNA and thiotrophic cbbL, which may suggest the feature of type X methanotrophs. These observations demonstrate that pogonophoran and vestimentiferan
worms have higher plasticity in bacterial symbioses than previously suspected. |
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Keywords: | Vestimentifera pogonophora endosymbiont thiotroph methanotroph |
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