title: Evidence for chemoautotrophic symbiosis in a Mediterranean cold seep clam (Bivalvia: Lucinidae): comparative sequence analysis of bacterial 16S rRNA, APS reductase and RubisCO genes.
abstract: Symbioses between lucinid clams (Bivalvia: Lucinidae) and autotrophic sulphide-oxidizing bacteria have mainly been studied in shallow coastal species, and information regarding deep-sea species is scarce. Here we study the symbiosis of a clam, resembling Lucinoma kazani, which was recently collected in sediment cores from new cold-seep sites in the vicinity of the Nile deep-sea fan, eastern Mediterranean, at depths ranging from 507 to 1691 m. A dominant bacterial phylotype, related to the sulphide-oxidizing symbiont of Lucinoma aequizonata, was identified in gill tissue by comparative 16S rRNA gene sequence analysis. A second phylotype, related to spirochete sequences, was identified twice in a library of 94 clones. Comparative analyses of gene sequences encoding the APS reductase alpha subunit and ribulose-1,5-bisphosphate carboxylase oxygenase support the hypothesis that the dominant symbiont can perform sulphide oxidation and autotrophy. Transmission electron micrographs of gills confirmed the dominance of sulphide-oxidizing bacteria, which display typical vacuoles, and delta(13)C values measured in gill and foot tissue further support the hypothesis for a chemoautotrophic-sourced host carbon nutrition.
authors.affiliation: UMR 7138, Adaptation aux milieux extrêmes, Université Pierre et Marie Curie, Paris, France. sduperro@snv.jussieu.fr
authors.forename: Sébastien
authors.initials: S
authors.lastname: Duperron
authors.forename: Aline
authors.initials: A
authors.lastname: Fiala-Médioni
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Caprais
authors.forename: Karine
authors.initials: K
authors.lastname: Olu
authors.forename: Myriam
authors.initials: M
authors.lastname: Sibuet
mesh_terms: D000818:Animals; D001419:Bacteria / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development*; D049872:Bivalvia / Q000235:genetics / Q000382:microbiology*; D052837:Chemoautotrophic Growth; D020563:Gammaproteobacteria / Q000201:enzymology / Q000235:genetics; D019083:Mediterranean Region; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry / Q000235:genetics*; D017421:Sequence Analysis; D013142:Spirochaeta / Q000201:enzymology / Q000235:genetics; D013559:Symbiosis
chemical_list: D012336:RNA, Ribosomal, 16S; D050862:Oxidoreductases Acting on Sulfur Group Donors; C019618:adenylylsulfate reductase; D012273:Ribulose-Bisphosphate Carboxylase