title: Heterogeneous composition of key metabolic gene clusters in a vent mussel symbiont population.
abstract: Chemosynthetic symbiosis is one of the successful systems for adapting to a wide range of habitats including extreme environments, and the metabolic capabilities of symbionts enable host organisms to expand their habitat ranges. However, our understanding of the adaptive strategies that enable symbiotic organisms to expand their habitats is still fragmentary. Here, we report that a single-ribotype endosymbiont population in an individual of the host vent mussel, Bathymodiolus septemdierum has heterogeneous genomes with regard to the composition of key metabolic gene clusters for hydrogen oxidation and nitrate reduction. The host individual harbours heterogeneous symbiont subpopulations that either possess or lack the gene clusters encoding hydrogenase or nitrate reductase. The proportions of the different symbiont subpopulations in a host appeared to vary with the environment or with the host's development. Furthermore, the symbiont subpopulations were distributed in patches to form a mosaic pattern in the gill. Genomic heterogeneity in an endosymbiont population may enable differential utilization of diverse substrates and confer metabolic flexibility. Our findings open a new chapter in our understanding of how symbiotic organisms alter their metabolic capabilities and expand their range of habitats.
authors.affiliation: Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Ikuta
authors.affiliation: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takaki
authors.affiliation: Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nagai
authors.affiliation: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shimamura
authors.affiliation: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Miwako
authors.initials: M
authors.lastname: Tsuda
authors.affiliation: Department of Subsurface Geobiological Analysis and Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kawagucci
authors.affiliation: Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Yui
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Inoue
authors.affiliation: Okinawa Industrial Technology Center, 12-2 Suzaki, Uruma, Okinawa, Japan.
authors.forename: Morimi
authors.initials: M
authors.lastname: Teruya
authors.affiliation: Okinawa Institute of Advanced Sciences (OIAS), 5-1 Suzaki, Uruma, Okinawa, Japan.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Satou
authors.affiliation: Okinawa Institute of Advanced Sciences (OIAS), 5-1 Suzaki, Uruma, Okinawa, Japan.
authors.forename: Kuniko
authors.initials: K
authors.lastname: Teruya
authors.affiliation: Okinawa Institute of Advanced Sciences (OIAS), 5-1 Suzaki, Uruma, Okinawa, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Shimoji
authors.affiliation: Okinawa Institute of Advanced Sciences (OIAS), 5-1 Suzaki, Uruma, Okinawa, Japan.
authors.forename: Hinako
authors.initials: H
authors.lastname: Tamotsu
authors.affiliation: Okinawa Institute of Advanced Sciences (OIAS), 5-1 Suzaki, Uruma, Okinawa, Japan.|Okinawa Science and Technology Promotion Center (OSTC), 112-18 Asahimachi, Naha, Okinawa, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirano
authors.affiliation: Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Maruyama
authors.affiliation: Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D017753:Ecosystem; D005798:Genes, Bacterial; D005880:Gills; D017403:In Situ Hybridization; D005810:Multigene Family; D049879:Mytilidae / Q000382:microbiology*; D010100:Oxygen / Q000737:chemistry; D016133:Polymerase Chain Reaction; D012623:Seawater / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D010100:Oxygen