HR: 0800h
AN: B21D-0915    [Abstracts]
TI: Microbial Community Evolution as Evidenced by Isotopic Incorporation into Phospholipid Fatty Acids in a Model Aquifer System
AU: * Morrison, L
EM: lmorrison@whoi.edu
AF: Dept. of Marine Chemistry & Geochemistry; Woods Hole Oceanographic Institution, 360 Woods Hole Rd. MS #25, Woods Hole, MA 02543 United States
AU: Mailloux, B J
EM: bjm2103@columbia.edu
AF: Columbia Earth Institute, 153 W. 116th Street, New York, NY 10027 United States
AU: Kujawinski, E B
EM: ekujawinski@whoi.edu
AF: Dept. of Marine Chemistry & Geochemistry; Woods Hole Oceanographic Institution, 360 Woods Hole Rd. MS #25, Woods Hole, MA 02543 United States
AB: Stable isotope probing (SIP) of biomarkers such as phospholipid fatty acids (PLFAs) has been used successfully to identify active microbial communities in a variety of environments. We are interested in extending this approach to examine the evolution of microbial communities over time. We tested this capability within the context of a larger experiment examining the role of microbes in mediating transformations of organic matter within an aquifer system. A laboratory flow-through column experiment was conducted with sediment collected from a pristine, shallow, coastal plain aquifer. The groundwater medium was amended with low levels of an isotopically labeled substrate, 13C-acetate, for approximately one month and then with non-labeled acetate for one month. PLFAs were extracted from sediments prior to and after labeled-acetate addition. In addition, PLFAs were isolated from effluent samples during selected time points within the two-month experiment. Incorporation of the 13C label into the PLFAs was monitored using isotope-ratio GC/MS. Because some PLFAs can be used to infer the presence of specific microbial groups, we used the relative concentration of different PLFAs and the timing and degree of isotopic incorporation (or loss) to examine the progression of different microbial communities within our model system. This powerful method can be used to untangle the complex interactions within microbial systems and can be extended to a variety of ecosystems.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting