Novel Marine Archaebacteria: Potential Contribution to Midwater Biomass and Activity

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This research investigation looks at newly discovered groups of archaebacteria found recently by molecular genetic analysis of marine bacterioplankton. DNA sequences from these organisms were recovered from samples collected at one site in the oligotrophic open Pacific Ocean at depths of 100m and 500m. This group made up most (70%) of the clones obtained from 500m, so there is a suggestion that they may be very important in the biomass and metabolism of deeper waters. Given the "unusual" nature of the niches ordinarily occupied by most archaebacteria in other habitats (extreme thermophiles, strictly anaerobic methanogens, extreme halophiles, etc.), this occurrence of archaebacteria may suggest unexpected metabolic and biogeochemical processes in the ocean's vast interior. Dr. Fuhrman will perform nucleic acid probe analysis on additional midwater and deep sea samples to see if this group of bacteria is repeatably found in the interior ocean, and if so, to estimate the relative abundance of these organisms compared to other types of microbes. He will repeat the sequence analysis in samples that test positive, to determine if the organisms are indistinguishable from those already found. Additionally, he will attempt the very difficult culturing from fresh seawater samples to determine if these organisms can be enriched and possibly isolated from seawater for laboratory study. Along with a marine organic geochemist, he will analyse lipids for types unique to archaebacteria. The conditions of enrichment plus information on the abundance of these organisms may indicate the significance of biogeochemical transformations mediated by these organisms. While the preliminary data indicate these organisms may be major contributors to midwater processes, there is a risk of not finding them again.