Riftia pachyptila symbiont

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Characteristics of the symbiont/pathogen

What kind of microbe is it (eg Cell morphology, shape, phylogenetic classification)? Is its genome sequenced, and if so, how big is the genome?

Characteristics of Riftia pachyptila

Riftia pachyptila is a giant tubeworm that inhabits the volcanic deep sea vents of the Pacific Ocean. A plume protrudes from the R. pachyptila protective tube and contacts the surrounding water. The plume has a large, highly vascularized surface which allows for the exchange of metabolites between R. pachyptila and the environment. Other tissues within the R. pachyptila tube include the vestimentum, which allows R. pachyptila to position itself in the tube, and the richly vascularized trophosome.[1] R. pachyptila does not have a digestive tract and must live in an obligate symbiosis with a sulfur-oxidizing chemoautotrophic bacterium. This mutualistic symbiosis is localized in the R. pachyptila trophosome cells, which are densely colonized by the bacterium. [2]. The bacterium is estimated to represent as much as 35% of the total volume of the trophosome [4]. R. pachyptila larvae have a digestive tract which disappears during development, so likely the trophosome must be colonized with the bacterium for each generation [3].

Riftia pachyptila with visible red plume due to hemoglobin NOAA

The circulatory system includes a pump located in the vestimentum region that promotes blood circulation in the entire body, including to the trophosome cells which bring nutrients to the bacterium. The plume is rich with blood, which can be visualized by the red color of the plume. The circulatory system mediates all metabolite exchanges between R. pachyptila and the surrounding water [4][5].R. pachyptila are adapted to their volcanic deep sea environment and use its composition, which include carbon, nitrogen, oxygen, and sulfur, in metabolic pathways that rely on the symbiotic relationship with the bacterium. The R. pachyptila hemoglobin is the transporter of both oxygen and sulfide to the bacterium which produce metabolic energy for both itself and R. pachyptila [6].

Host-Symbiont Interaction

What kind of interaction do host and symbiont have? How is the host affected by the relationship? How does the host acquire and transmit the symbiont? Is the interaction obligate or facultative?

Molecular Insights into the Symbiosis

Describe molecular/genetic studies on the symbiosis.

Ecological and Evolutionary Aspects

What is the evolutionary history of the interaction? Do particular environmental factors play a role in regulating the symbiosis?

Recent Discoveries

Describe two findings on the symbiosis published within the last two years.

References

[Sample reference] [[1] Seemanapalli SV, Xu Q, McShan K, Liang FT. 2010. Outer surface protein C is a dissemination-facilitating factor of Borrelia burgdorferi during mammalian infection. PLoS One 5:e15830.]

1) Gaill, F. (1993) Aspects of life development at deep sea hydrothermal vents. FASEB J. 7, 558–565.

2) Hand, S.C. (1987) Trophosome ultrastructure and the characterization of isolated bacteriocytes from invertebrate-sulfur bacteria symbioses. Biol. Bull. 173, 260–276.

3) Edwards, D.B., Nelson, D.C. (1991) DNA-DNA Solution Hybridization Studies of the Bacterial Symbionts of Hydrothermal Vent Tube Worms (Riftia pachyptila and Tevnia jerichonana). Appl Environ Microbiol. 5:1082–1088

4) Zal, F., Lallier, F.H., Green, B.N., Vinogradov, S.N. & Toulmond, A. (1996) The multi-hemoglobin system of the hydrothermal vent tube worm Riftia pachyptila. II. Complete polypeptide chain composition investigated by maximum entropy analysis of mass spectra. J. Biol. Chem. 271, 8875–8881.

5) Zal, F., Lallier, F.H., Wall, J.S., Vinogradov, S.N. & Toulmond, A. (1996) The multi-hemoglobin system of the hydrothermal vent tube worm Riftia pachyptila. I. Reexamination of the number and masses of its constituents. J. Biol. Chem. 271, 8869–8874.

6) Goffredi, S.K., Childress, J.J., Desaulniers, N.T. & Lallier, F.J.(1997) Sulfide acquisition by the vent worm Riftia pachyptila appears to be via uptake of HS–, rather than H2S. J. Exp. Biol. 200, 2609–2616.

Edited by [Crystal Leibrand], students of Grace Lim-Fong

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