Eighteen strains of flagellated protists representing 9 species were isolated and cultured from four deep-sea hydrothermal vents: Juan de Fuca Ridge (2200 m), Guaymas Basin (2000 m), 21 Degrees North (2550 m) and 9 Degrees North (2000 m). The hydrothermal vent flagellates belonged to six different taxonomic orders: the Ancyro-monadida, Bicosoecida, Cercomonadida, Choanoflagellida, Chryso-monadida, and Kinetoplastida. Molecular and morphological evidence point to one of the isolates Ancyromonas as a plausible candidate for the closest relative to the common ancestor of Metazoans, Fungi, and Choanoflagellates (the Opisthokonta). Using 18S rDNA sequences from most of the major eukaryotic lineages, maximum likelihood, minimum evolution and maximum parsimony analyses yielded con-gruent phylogenies supporting this hypothesis.

Deep-sea vent samples were both cultured to select for kine-toplastid flagellates and analyzed without culturing by denaturing gradient gel electrophoresis (DGGE) using PCR primers specific to the kinetoplastid clade. By comparing these two different methods of analysis, our goal was to decrease the biases and/or errors inher-ent in either method alone and to improve our ability to assess flag-ellate diversity and distribution in remote vent environments. PCR and DGGE were able to specifically isolate and amplify target DNA's from all cultured kinetoplastid species in matching vent samples, thus corroborating the findings of culturing. Molecular methods had the additional ability to detect species presence where culturing did not, thereby providing a better indication of the distribution of these species.

Many of the vent isolates are ubiquitous members of marine, freshwater, and terrestrial ecosystems worldwide, suggesting a global distribution of these flagellate species. This discovery ad-vanced the hypothesis that ubiquity in distribution patterns among heterotrophic flagellates implies high tolerance and/or adaptability to a wide range of environmental conditions. Experiments under vent conditions of high pressure and high concentrations of metals and sulfide showed that some of these species are very tolerant to ex-treme environmental conditions.