HR: 1330h
AN: NB33C-10    [Abstracts]
TI: Modification of the ³H-leucine Incorporation Technique for Quantifying Rates of Bacterial Secondary Production on Decaying Wetland Plant Litter: Effectiveness of Microdialysis.
AU: * Gillies, J E
EM: jgillies@emich.edu
AF: Department of Biology, Eastern Michigian University, 316 Mark Jefferson, Ypsilanti, MI 48197 United States
AU: Francoeur, S N
EM: steve.francoeur@emich.edu
AF: Department of Biology, Eastern Michigian University, 316 Mark Jefferson, Ypsilanti, MI 48197 United States
AU: Kuehn, K A
EM: kkuehn@emich.edu
AF: Department of Biology, Eastern Michigian University, 316 Mark Jefferson, Ypsilanti, MI 48197 United States
AB: The radiolabelled ³H-leucine incorporation technique for quantifying rates of bacterial production has increased in popularity since its original description for bacterioplankton communities. Prior studies addressing incorporation conditions (e.g., substrate saturation) for bacterial communities in other habitats, such as decaying plant litter, have reported a wide range of final leucine concentrations (400nM to 50,000nM) to achieve saturation-level uptake. We assessed the application of the ³H-leucine incorporation procedure for measuring bacterial production on decaying wetland plant litter. Substrate saturation experiments (9 concentrations, 10nM to 50,000nM final leucine) were conducted for bacterial communities colonizing submerged litter of three emergent plant species (Typha angustifolia, Schoenoplectus validus, and Phragmites australis). A modified ³H-leucine protocol was developed by coupling previously described incubation and extraction protocols with microdialysis (500MWCO) of the final radiolabelled protein extract. Incorporation of ³H-leucine into protein exhibited a biphasic saturation curve, with lower Km values ranging from 400nM to 1200nM depending on the plant species studied. Upper Km values ranged from 4000nM to 6000nM. Dialysis of the crude protein extract significantly improved counting precision and the signal-to-noise ratio. These results suggest differential uptake by litter associated microbial assemblages, with lower Km values possibly representing bacterial uptake and higher Km values representing non-bacterial uptake.
DE: 1615 Biogeochemical processes (4805)
DE: 4239 Limnology
DE: 4803 Bacteria
DE: 4840 Microbiology
DE: 9903 NABS Student Award Methodology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly