title: Host-symbiont relationships in hydrothermal vent gastropods of the genus Alviniconcha from the Southwest Pacific.
abstract: Hydrothermal vent gastropods of the genus Alviniconcha are unique among metazoans in their ability to derive their nutrition from chemoautotrophic gamma- and epsilon-proteobacterial endosymbionts. Although host-symbiont relationships in Alviniconcha gastropods from the Central Indian Ridge in the Indian Ocean and the Mariana Trough in the Western Pacific have been studied extensively, host-symbiont relationships in Alviniconcha gastropods from the Southwest Pacific remain largely unknown. Phylogenetic analysis using mitochondrial cytochrome c oxidase subunit I gene sequences of host gastropods from the Manus, North Fiji, and Lau Back-Arc Basins in the Southwest Pacific has revealed a new host lineage in a Alviniconcha gastropod from the Lau Basin and the occurrence of the host lineage Alviniconcha sp. type 2 in the Manus Basin. Based on 16S rRNA gene sequences of bacterial endosymbionts, two gamma-proteobacterial lineages and one epsilon-proteobacterial lineage were identified in the present study. The carbon isotopic compositions of the biomass and fatty acids of the gastropod tissues suggest that the gamma- and epsilon-proteobacterial endosymbionts mediate the Calvin-Benson cycle and the reductive tricarboxylic acid cycle, respectively, for their chemoautotrophic growth. Coupling of the host and symbiont lineages from the three Southwest Pacific basins revealed that each of the Alviniconcha lineages harbors different bacterial endosymbionts belonging to either the gamma- or epsilon-Proteobacteria. The host specificity exhibited in symbiont selection provides support for the recognition of each of the host lineages as a distinct species. The results from the present study also suggest the possibility that Alviniconcha sp. types 1 and 2 separately inhabit hydrothermal vent sites approximately 120 m apart in the North Fiji Basin and 500 m apart in the Manus Basin.
authors.affiliation: Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology, Yokosuka, Kanagawa 237-0061, Japan. yohey@jamstec.go.jp
authors.forename: Yohey
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kojima
authors.forename: Takenori
authors.initials: T
authors.lastname: Sasaki
authors.forename: Masae
authors.initials: M
authors.lastname: Suzuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Utsumi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Urakawa
authors.forename: Shinji
authors.initials: S
authors.lastname: Tsuchida
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.forename: Hisako
authors.initials: H
authors.lastname: Hirayama
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
authors.forename: Koki
authors.initials: K
authors.lastname: Horikoshi
mesh_terms: D000818:Animals; D002244:Carbon / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004272:DNA, Mitochondrial / Q000235:genetics / Q000302:isolation & purification; D003576:Electron Transport Complex IV / Q000235:genetics; D020565:Epsilonproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D049851:Gastropoda / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000382:microbiology*; D008969:Molecular Sequence Data; D010140:Pacific Ocean; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013559:Symbiosis
chemical_list: D004269:DNA, Bacterial; D004272:DNA, Mitochondrial; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D002244:Carbon; D003576:Electron Transport Complex IV