Microbial metabolism of model pesticides in the drilosphere and effect on N2 O production: Linking processes with populations

Principle investigators: Dr. M.A. Horn, Prof. Dr. H.L. Drake

Co-workers: Y. Liu, A. Ramm, A. Zaprasis

1. The drilosphere (i.e., burrow linings, gut content, and casts) harbours hitherto unknown, highly active prokaryotes that transform phenoxyacetic acid herbicides and their degradation products.
2. Phenoxyacetic acid herbicides and their degradation products inhibit N2 O production and growth of hitherto unknown nitrifiers and denitrifiers in the drilosphere.

To assess the microbiology of the drilosphere
1.Fate of pesticides and degradation products (MCPA and 2,4-DCP)
2.Effect of pesticides on N2 O production by denitrifiers and nitrifiers
3.Identify and isolate key prokaryotes associated with pesticide degradation and N2 O production


Degradation intermediates and products will be determined by gas chromatography (GC) and high performance liquid chromatography with mass spectrometry (HPLC-MS). Sorption and mineralization of pesticides will be determined by 14C tracer analyses. 16S rRNA and mRNA based stable isotope probing (SIP), quantification of functional genes by quantitative PCR (qPCR), most probable number (MPN) analyses, and directed isolation techniques will be utilized to identify and characterize process-associated microbial populations and microorganisms.

Dr. Michael Schloter



Poster Horn 


Liu, Y.J., Zaprasis, A., Liu, S.J., Drake, H.L., Horn, M.A. 2011. The earthworm Aporrectodea caliginosa stimulates abundance and activity of phenoxyalkanoic acid herbicide degraders. ISME J. 5, 473-485.

Liu, Y.J., Liu, S.J., Drake, H.L., Horn, M.A. 2011. Alphaproteobacteria dominate active 2-methyl-4-chlorophenoxyacetic acid herbicide degraders in agricultural soil and drilosphere. Environ. Microbiol. 13, 991-1009.

Zaprasis, A., Liu, Y.J., Liu, S.J., Drake, H.L., Horn, M.A. 2010. Abundance of novel and diverse tfdA-like genes, encoding putative phenoxyalkanoic acid herbicide-degrading dioxygenases, in soil. Appl. Environ. Microbiol. 76, 119-128.