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2011
Markert, S, Gardebrecht A, Felbeck H, Sievert SM, Klose J, Becher D, Albrecht D, Thurmer A, Daniel R, Kleiner M, Hecker M, Schweder T.  2011.  Status quo in physiological proteomics of the uncultured Riftia pachyptila endosymbiont. Proteomics. 11:3106-3117.   10.1002/pmic.201100059   AbstractWebsite

Riftia pachyptila, the giant deep-sea tube worm, inhabits hydrothermal vents in the Eastern Pacific ocean. The worms are nourished by a dense population of chemoautotrophic bacterial endosymbionts. Using the energy derived from sulfide oxidation, the symbionts fix CO(2) and produce organic carbon, which provides the nutrition of the host. Although the endosymbionts have never been cultured, cultivation-independent techniques based on density gradient centrifugation and the sequencing of their (meta-) genome enabled a detailed physiological examination on the proteomic level. In this study, the Riftia symbionts' soluble proteome map was extended to a total of 493 identified proteins, which allowed for an explicit description of vital metabolic processes such as the energy-generating sulfide oxidation pathway or the Calvin cycle, which seems to involve a reversible pyrophosphate-dependent phosphofructokinase. Furthermore, the proteomic view supports the hypothesis that the symbiont uses nitrate as an alternative electron acceptor. Finally, the membrane-associated proteome of the Riftia symbiont was selectively enriched and analyzed. As a result, 275 additional proteins were identified, most of which have putative functions in electron transfer, transport processes, secretion, signal transduction and other cell surface-related functions. Integrating this information into complex pathway models a comprehensive survey of the symbiotic physiology was established.

1992
Polz, MF, Felbeck H, Novak R, Nebelsick M, Ott JA.  1992.  Chemoautotrophic, sulfur-oxidizing symbiotic bacteria on marine nematodes: Morphological and biochemical characterization. Microbial Ecology. 24:313-329.   10.1007/bf00167789   AbstractWebsite

The marine, free-living Stilbonematinae (Nematoda: Desmodorida) inhabit the oxygen sulfide chemocline in marine sands. They are characterized by an association with ectosymbiotic bacteria. According to their ultrastructure the bacteria are Gram-negative and form morphologically uniform coats that cover the entire body surface of the worms. They are arranged in host-genus or host-species specific patterns: cocci form multilayered sheaths, rods, and crescent- or filament-shaped bacteria form monolayers. The detection of enzymes associated with sulfur metabolism and of ribulose- 1,5 bisphosphate carboxylase oxygenase, as well as elemental sulfur in the bacteria indicate a chemolithoautotrophic nature of the symbionts. Their reproductive patterns appear to optimize space utilization on the host surface: vertically standing rods divide by longitudinal fission, whereas other bacteria form nonseptate filaments of up to 100 mum length.