Bacterial symbiont of Riftia pachyptila

Functional genome analysis of the bacterial symbiont of the deep sea tubeworm Riftia pachyptila

FThe tubeworm Riftia pachyptila (Vestimentifera) is one of the main inhabitants of the hydrothermal vents of the east Pacific Rise. R. pachyptila lacks a digestive tract entirely. This tubeworm houses a dense population of intracellular, sulfide-oxidizing bacteria, which provide the nutriments to the animal. The chemoautotrophic bacterial symbionts fix carbon dioxide from the ambient sea water using the energy gained from oxidation of sulfide. Organic CO2 fixation products, mainly succinate and malate, are secreted by the bacteria into the blood of the animal.



Drawn according to Childress et al. (1987): Symbiosis in the Deep Sea. Scientific American 255, 115-120


The recent genome sequencing of the uncultivable symbionts of R. pachyptila by a Californian consortium coordinated by Prof. Dr. Horst Felbeck from Scripps Institution of Oceanography (SIO), University of California, San Diego (UCSD) allows a new approach to investigate this highly integrated symbiosis.

In cooperation with the group of Horst Felbeck we have started to analyze gene expression profiles of the bacterial symbionts of R. pachyptila under defined environmental conditions on the protein and mRNA level. The goal of these investigations is a better understanding of the physiological potential and the elucidation of as yet unknown gene functions of the bacterial symbionts. For this purpose, the cytoplasmic and the extracellular proteome of the Riftia symbionts is being analyzed by means of two-dimensional polyacrylamide gel electrophoresis (2D PAGE). The protein spots are identified by mass spectrometric techniques. The proteome of the bacterial symbionts of several R. pachyptila from different vent origins, incubated under defined environmental conditions will be analyzed. Thereby we hope to get a survey of the active genes of the bacteria in response to different nutrient conditions. The analysis of the extracellular proteome of the bacterial symbionts will provide information on the presence of potential exotoxins or antimicrobial enzymes, which could play a role in establishing this symbiosis.