Within the last 10 years, deep-sea hydrothermal vents of the Galapagos Rift, Guaymas Basin and other sites have been discovered to contain densely populated, metabolically active animal communities. These communities, living in permanent darkness and having a high degree of spatial isolation from similar communities, base their food chains largely on lithoautotrophic bacteria rather than on products transported from the photic zone. Lithoautotrophic bacteria are those which oxidize reduced inorganic compounds (e.g. hydrogen sulfide) to generate useful energy. They produce organic compounds from the precursor carbon dioxide and occur at the vents principally as symbionts within tissues of worms, clams and mussels. To date none of these symbionts has been cultured apart from the host organism. These investigations will (1) test numerous approaches for cultivation of the symbiont of the Galapagos vent mussel, (2) clam species, (3) complete purification of the bacterial DNA from numerous individual tube worms (Riftia pachyptila) from widely seperated vent sites. By using the method of DNA:DNA hybridization the fine-scale evolutionary relationships between these currently very disjunct populations will be defined.
