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Estimating rates of denitrification enzyme activity in wetland soils and direct simultaneous quantification of nitrogen and nitrous oxide by membrane inlet mass spectrometry
Citation:
Genthner, F., D. Marcovich, AND J. Lehrter. Estimating rates of denitrification enzyme activity in wetland soils and direct simultaneous quantification of nitrogen and nitrous oxide by membrane inlet mass spectrometry. Journal of Microbial & Biochemical Technology . OMICS Publishing Group, LOS ANGELES , CA, 5(4):095-101, (2013).
Impact/Purpose:
Develop MIMS based method for measuring denitrification enzyme activity
Description:
Denitrification enzyme activity (DEA) was measured in short-term (4 h) anaerobic assays using Membrane Inlet Mass Spectrometry (MIMS) and electron capture gas chromatography (GC-ECD). Using MIMS, modifications of the instrument and sample handling allowed for the simultaneous measurement of nitrous oxide (N2O) and dinitrogen (N2). Rate determinations were made from the slope of a linear curve generated by plotting increasing concentrations of the reaction products with time. Strong evidence for the validity of MIMS measured DEA rates was provided by showing consistent, linear accumulations of N2O or N2 and close agreement in rates from replicate reactions. Reactions were performed using wetland soils and cultures of Pseudomonas aeruginosa and P. chloroaphis that generated denitrification end products of N2 and N2O, respectively. Under acetylene inhibition P. aeruginosa produced the N2O end product at a rate equivalent to the rate obtained in the uninhibited reaction that produced N2. No significant (p>0.05) difference was observed between MIMS or headspace with GC-ECD, determined DEA in wetland soil reactions under acetylene inhibition. Because of anoxic conditions in the reaction vessels used with MIMS, detectable rates of N2O accumulation were only observed in acetylene blocked reactions or in cultures of P. chloroaphis. Methods developed here are designed to improve our understanding of conditions regulating denitrification and its benign (N2) and harmful (N2O) end-products.
