HR: 1340h
AN: B13A-1046    [Abstracts]
TI: Identification of active dehalorespiring microbial populations in anoxic river sediment by RNA-based stable isotope probing
AU: Kittelmann, S
B13A-1046 AF: Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Strasse, Marburg, D-35043 Germany
AU: * Friedrich, M W
EM: michael.friedrich@staff.uni-marburg.de
AF: Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Strasse, Marburg, D-35043 Germany
AB: Tetrachloroethene (perchloroethylene, PCE), a persistent contaminant in aquifers, soils and sediments, can be reductively dechlorinated by anaerobic microorganisms in a process referred to as dehalorespiration. However, the biodiversity of dehalorespiring microorganisms and their distribution especially in pristine environments is largely unexplored. Therefore, the aim of this study was to detect potentially novel PCE-dehalorespiring microorganisms by using stable isotope probing (SIP), a technique that allows to directly identify the function of uncultivated microbial populations. We simulated a PCE contamination by incubating pristine river sediment in the presence of PCE at a steady, low aqueous concentration (20 μM). Dehalogenation activity in microcosms (20 nmol cis-dichloroethene per ml slurry per day formed) was detected already after 4 weeks at 20°C with sediment indigenous electron donors. The microbial community in sediment incubations was probed with ¹³C-labelled acetate (0.5 mM) as electron donor and carbon source at 15°C for 3 days. After RNA extraction, "heavy" ¹³C-rRNA and light ¹²C-rRNA were separated by isopycnic centrifugation, and Bacteria-related populations in gradient fractions were characterised by terminal restriction fragment length polymorphism analysis and cloning. In heavy gradient fractions from the microcosm with PCE, we detected a prominent 506-bp terminal restriction fragment (T-RF) and a few minor T-RFs only. In contrast, in the control without PCE, Bacteria-specific rRNA was restricted to light gradient fractions, and the prominent T-RFs found in the PCE-dechlorinating microcosm were of minor importance. Apparently, ¹³C-acetate was incorporated into bacterial rRNA more effectively in PCE-respiring microcosms. Thus, rRNA-SIP provides strong evidence for the presence of PCE-dehalorespiring, ¹³C-acetate-utilising populations in river sediment microcosms. Cloning/sequencing analysis identified the prominent members of the heavy gradient fractions as members of the phylum Chloroflexi only distantly related to cultivated dechlorinating Dehalococcides spp.
DE: 0410 Biodiversity
DE: 0418 Bioremediation
DE: 0448 Geomicrobiology
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
SC: Biogeosciences [B]
MN: Fall Meeting 2005