Microbial Metabolism of Model Pesticides in the Drilosphere and Effect on N2O Production: Linking Processes with Populations (SPP 1315)
DFG HO 4020/1-1
From 02/2007 to 03/2013Principal Investigator: Marcus A. Horn, Harold L. Drake
Pesticides are widely used in agriculture. Mineralization of pesticides occurs in soil, mainly due to aerobic microbial processes. Hotspots of microbial activity in soils include the drilosphere, i.e., burrows, gut content, and casts of earthworms. The greenhouse gas nitrous oxide (N2O) is produced in the drilosphere due to ongoing nitrification and denitrification, which might be affected by pesticides. However, the physico-chemical parameters, aerobic and anaerobic degradation pathways of pesticides, and associated pesticide–degrading organisms in the drilosphere are poorly resolved. The effects of pesticides and their degradation products on nitrification and denitrification in the drilosphere are largely unknown. Based on these deficiencies of information, the following hypotheses will be tested (using soil columns with earthworms): (i) the drilosphere harbors hitherto unknown, highly active prokaryotes that transform phenoxyacetic acid herbicides and their degradation products; and (ii) phenoxyacetic acid herbicides and their degradation products inhibit N2O production and growth of hitherto unknown nitrifiers and denitrifiers in the drilosphere. Degradation intermediates and products will be determined by gas chromatography (GC) and high performance liquid chromatography with mass spectrometry (HPLC-MS). 16S rRNA and mRNA based stable isotope probing (SIP), quantification of functional genes by quantitative ‘real time’ PCR (qPCR), most probable number (MPN) analyses, and directed isolation techniques will be utilized to identify and characterize process-associated microbial populations and micro-organisms.
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