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2017
Ponnudurai, R, Sayavedra L, Kleiner M, Heiden SE, Thurmer A, Felbeck H, Schluter R, Sievert SM, Daniel R, Schweder T, Markert S.  2017.  Genome sequence of the sulfur-oxidizing Bathymodiolus thermophilus gill endosymbiont. Standards in Genomic Sciences. 12   10.1186/s40793-017-0266-y   AbstractWebsite

Bathymodiolus thermophilus, a mytilid mussel inhabiting the deep-sea hydrothermal vents of the East Pacific Rise, lives in symbiosis with chemosynthetic Gammaproteobacteria within its gills. The intracellular symbiont population synthesizes nutrients for the bivalve host using the reduced sulfur compounds emanating from the vents as energy source. As the symbiont is uncultured, comprehensive and detailed insights into its metabolism and its interactions with the host can only be obtained from culture-independent approaches such as genomics and proteomics. In this study, we report the first draft genome sequence of the sulfur-oxidizing symbiont of B. thermophilus, here tentatively named Candidatus Thioglobus thermophilus. The draft genome (3.1 Mb) harbors 3045 protein-coding genes. It revealed pathways for the use of sulfide and thiosulfate as energy sources and encodes the Calvin-Benson-Bassham cycle for CO2 fixation. Enzymes required for the synthesis of the tricarboxylic acid cycle intermediates oxaloacetate and succinate were absent, suggesting that these intermediates may be substituted by metabolites from external sources. We also detected a repertoire of genes associated with cell surface adhesion, bacteriotoxicity and phage immunity, which may perform symbiosis-specific roles in the B. thermophilus symbiosis.

1995
Felbeck, H, Turner PJ.  1995.  CO2 transport in catheterized hydrothermal vent tubeworms, Riftia pachyptila (vestimentifera). Journal of Experimental Zoology. 272:95-102.   10.1002/jez.1402720203   AbstractWebsite

Isolated plumes and vestimenta of the tubeworm Riftia pachyptila were perfused to determine the form in which carbon is transported to the animal's symbionts via the circulatory system. Catheters supplying colored saline were inserted into an afferent blood vessel while samples were collected from the efferent vessel. During perfusion, the plumes were immersed in sea water containing radiolabeled CO2. The effluent showed radioactivity in inorganic carbonate (Sigma CO2, sum of all forms), malate, and succinate. When isolated vestimenta were perfused with saline containing labeled CO2, labeled malate and succinate could be detected in the effluent. Carbon transport in the blood as Sigma CO2 is estimated to be of similar importance to that transported after incorporation into organic carbon. The significance for the establishment of the carbon isotope ratio of tubeworms is discussed. (C) 1995 Wiley-Liss, Inc.

1993
Fiala-Medioni, A, Boulegue J, Ohta S, Felbeck H, Mariotti A.  1993.  Source of energy sustaining the Calyptogena populations from deep trenches in subduction zones off Japan. Deep-Sea Research Part I-Oceanographic Research Papers. 40:1241-1258.   10.1016/0967-0637(93)90136-q   AbstractWebsite

Deep tow camera surveys during the Hakuho Maru cruise (KH-89-1) and Nautile dives during the Kaiko-Nankai cruise (November 1989) demonstrate the presence of dense animal communities at depths around 2000 and 3800 m. The dominant organisms are vesicomyid bivalve molluscs, with two new very large (up to 28 cm long) species of Calyptogena and the two species previously found in the Nankai Trough during the Kaiko cruise (1985), C. laubieri and C. kaikoi. They apparently rely on sulfide-based chemoautotrophy through symbiotic bacteria associated with their gills. Evidence of sulfur-oxidizing metabolism includes ultrastructural features of symbionts, absence of methanol dehydrogenase activity, presence of ATP-sulfurylase and abundant elemental sulfur in the gill. Carbon isotope ratios are close to values obtained in other sulfur-oxidizing symbiont-bearing species (from -35.6 to -38.7 parts per thousand for the 3950 m species and from -36 to -37.4 parts per thousand for the 2050 m species). Nitrogen isotope ratios show highly variable values (from -4 to -9.7 parts per thousand for the 3950 m species and from -0.2 to +4.4 parts per thousand for the 2050 m species). C-14 analyses indicates growth based on water CO2 with limited or no input of fossil carbon.