Characterization of a novel spirochete associated with the hydrothermal vent polychaete annelid, Alvinella pompejana

A highly integrated, morphologically diverse bacterial community is associa ted with the dorsal surface of Alvinella pompejana, a polychaetous annelid that inhabits active high-temperature deep-sea hydrothermal vent sites alon g the East Pacific Rise (EPR). Analysis of a previously prepared bacterial 16S ribosomal DNA (rDNA) library identified a spirochete most closely relat ed to an endosymbiont of the oligochete Olavius loisae. This spirochete phy lotype (spirochete A) comprised only 2.2% of the 16S rDNA clone library but appeared to be much more dominant when the same sample was analyzed by den aturing gradient gel electrophoresis (DGGE) and the terminal restriction fr agment length polymorphism procedure (12 to 18%). PCR amplification of the community with spirochete specific primers used in conjunction with DGGE an alysis identified two spirochete phylotypes. The first spirochete was ident ical to spirochete A but was present in only one A. pompejana specimen. The second spirochete (spirochete B) was 84.5% similar to spirochete a and, mo re interestingly, was present in the epibiont communities of all of the A. pompejana specimens sampled throughout the geographic range of the worm (13 degreesN to 32 degreesS along the EPR). The sequence variation of the spir ochete B phylotype was less than 3% for the range of A. pompejana specimens tested, suggesting that a single spirochete species was present in the A. pompejana epibiotic community. Additional analysis of the environments surr ounding the worm revealed that spirochetes are a ubiquitous component of hi gh-temperature vents and may play an important role in this unique ecosyste m.