HR: 0800h
AN: B21A-1015    [Abstracts]
TI: Archaeal and Bacterial Variation Across Geochemical Gradients in an Arsenic-Rich, Shallow Submarine Vent, Papua New Guinea
AU: * Meyer-Dombard, D R
EM: darmeyer@artsci.wustl.edu
AF: Massachusetts Institute of Technology, 42-44 Carleton St., Cambridge, MA 02142 United States
AU: Osburn, M R
EM: mrosburn@artsci.wustl.edu
AF: Washington University, 1 Brookings Dr., St. Louis, MO 63130 United States
AU: Amend, J P
EM: amend@levee.wustl.edu
AF: Washington University, 1 Brookings Dr., St. Louis, MO 63130 United States
AB: Near the Feni Islands of Papua New Guinea, reduced hydrothermal fluids mix with seawater, establishing redox disequilibria that may serve as energy sources for chemotrophic Archaea and Bacteria. Of particular interest are elevated arsenite concentrations (1000 μg/L) in the vent water and arsenate-rich ferrihydrite deposits (up to 7 wt.%) that envelope the sediment and coral. In sediment pore waters out to > 200m from the vents, a steeply decreasing arsenic gradient is observed. To establish a baseline of microbial community composition at the vent fluid-seawater interface, bulk DNA was extracted from ferrihydrite coatings, then amplified (16S rRNA, targeting both Archaea and Bacteria), cloned, and sequenced. Red and green biofilms associated with the coatings revealed archaeal communities exclusively composed of deeply-branching, uncultured Crenarchaea. The bacterial members of the community differed in the two biofilms; the red biofilm is primarily composed of gamma Proteobacteria, Chloroflexis, and Planctomycetes, but 60% of clones from the green biofilm community affiliates with the alpha Proteobacteria and candidate group OP11. The remaining portion of the bacterial community in the red coating is made of Thermotogales, Aquificales, Thermales phylotypes and uncultured Bacteria, while OP10, Chloroflexis and Plantomycetales complete the community in the green coatings. No clones associating with thermophilic bacterial groups were found in the green coatings. To provide a comparison to the vent source communities, a sediment core was taken 2.5m from the vent and two depths (10 and 40cm) were analyzed by similar molecular analysis. In both core horizons, the archaeal community is composed of > 75% uncultured Crenarchaea, similar to phylotypes found in deep-sea and terrestrial hydrothermal locations, with the remainder of the communities from known crenarchaeal phylotypes. The bacterial communities are primarily Chloroflexis and gamma Proteobacteria-like phylotypes: 25% and 30% respectively at 10cm depth; 45% and 25% at 40cm. A few representatives from thermophilic groups (Thermotogales and Aquificales) were found in both horizons. Organisms in these biofilms and sediments may be paramount to the removal of arsenic from this ecosystem and have relevance to remediation efforts in areas of contamination. Geochemical and physiochemical conditions (UV exposure, temperature and diffuse vs. focused flow) are expected to influence community composition at each location.
DE: 0406 Astrobiology and extraterrestrial materials
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0456 Life in extreme environments
DE: 0463 Microbe/mineral interactions
SC: Biogeosciences [B]
MN: Fall Meeting 2005