A survey of flagellate diversity at four deep-sea hydrothermal vents in the Eastern Pacific Ocean using structural and molecular approaches

Eighteen strains of flagellated protists representing nine species were iso lated and cultured front four deep-sea hydrothermal vents: Juan de Fuca Rid ge (2,200 m), Guaymas Basin (2,000 m), 21 degrees N (2,550 m) and 9 degrees N (2,000 m). Light and electron microscopy were used to identify flagellat es to genus and, when possible, species. The small subunit ribosomal RNA ge nes of each vent species and related strains from shallow-waters and the Am erican Type Culture Collection were sequenced then used for comparative ana lysis with database sequences to place taxa in an rDNA tree. The hydrotherm al vent flagellates belonged to six different taxonomic orders: the Ancyrom onadida, Bicosoecida, Cercomonadida, Choanoflagellida, Chrysomonadida, and Kinetoplastida. Comparative analysis of vent isolate and database sequences resolved systematic placement of some well-known species with previously u ncertain taxonomic affinities, such as Ancyromonas sigmoides, Caecitellus p arvulus, and Mussisteria marina. Many of these vent isolates are ubiquitous members of marine, freshwater, and terrestrial ecosystems worldwide, sugge sting a global distribution of these flagellate species.