Abstract
A large, intact sulfide chimney, designated Finn, was recovered from the Mothra Vent Field on the Juan de Fuca Ridge in 1998. Finn was venting 302 degrees C fluids on the seafloor and contained complex mineralogical zones surrounding a large open central conduit. Examination of microorganisms within these zones, followed by community analysis with oligonucleotide probes, showed that there were variations in the abundance and diversity of eubacteria and archaea from the exterior to the interior of the chimney. The microbial abundance based upon epifluorescence microscopy and quantitative fatty acid analyses varied from >10(8) cells/g of sulfide 2 to 10 cm within the chimney wall to <10(5) cells/g in interior zones. Direct microscopic observation indicated that microorganisms were attached to mineral surfaces throughout the structure. Whole-cell hybridization results revealed that there was a transition from a mixed community of eubacteria and archaea near the cool exterior of the chimney to primarily archaea near the warm interior. Archaeal diversity was examined in three zones of Finn by cloning and sequencing of the 16S rRNA gene. The majority of sequences from the exterior of the chimney were related to marine group I of the Crenarchaeota and uncultured Euryarchaeota from benthic marine environments. In contrast, clone libraries from interior regions of the chimney contained sequences closely related to methanogens, Thermococcales, and Archaeoglobales, in addition to uncultured crenarchaeal phylotypes obtained from deep subsurface sites. These observations of microbial communities within an active hydrothermal chimney provide insight into the microbial ecology within such structures and may facilitate follow-up exploration into expanding the known upper temperature limits of life.