HR: 0800h
AN: B31A-0200    [Abstracts]
TI: Methanogenic Diversity in Marine Sediments at Hydrate Ridge, Oregon
AU: * Kendall, M M
EM: kendallm@pdx.edu
AU: Boone, D R
EM: booned@pdx.edu
AB: Little is known about the mechanism of methanogenic degradation of acetate or the fate of hydrogen and formate in cold marine sediments, or the ability of methanogens to grow and produce methane there. We used cultivation and molecular techniques to examine the microbes that produce methane from these substrates in permanently cold, anoxic marine sediments at Hydrate Ridge, Oregon ($44\deg$35'N, $125\deg$10'W, depth 800 m). Sediment samples (15 to 35 cm deep) were collected from areas of active methane ebullition or areas where methane hydrates occurred. The samples were anoxically diluted and inoculated into enrichment media with formate, acetate, or trimethylamine as catabolic substrate. After 2 years incubation at $4\deg$C to $15\deg$C, enrichment cultures grew and produced methane. DNA was extracted from the highest dilutions that grew. The sequence data suggested that each enrichment culture contained a single strain of methanogen, and many of these sequences were dissimilar to known sequences of methanogens. This level of similarity (89 to 91% similar) suggests that these methanogens belong to novel genera. A clone library of 16S rRNA genes was also created from DNA extracted from the sediment samples. Analysis of the 16S rRNA gene libraries also revealed phylotypes that were only distantly related to cultivated organisms. The sequences of the clone library and of the enrichment cultures indicate a high degree of phylogenetic diversity among the Hydrate Ridge Archaea.
DE: 3022 Marine sediments--processes and transport
DE: 1030 Geochemical cycles (0330)
DE: 1615 Biogeochemical processes (4805)
DE: 0330 Geochemical cycles
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting