This is the homepage for the project 'Synergism between Fungi and Bacteria in the Mineralisation of pesticides in soil'.
The project is a collaboration between the Geological Survey of Denmark and Greenland (GEUS) and the University of Copenhagen
The project is funded by the Danish Technical Research Council.
Background
The intensive use of pesticides has resulted in contamination of soil and subsequent migration of pesticides or degradation products to the groundwater. Microbial degradation play a key role for the fate of pesticides: whether they are degraded completely or transformed into new metabolites. These processes will influence the leaching of the compounds to ground- and surface waters.
The microbial degradation of a specific compound may not be restricted to a single micro-organism. Often different micro-organisms or consortia are involved. In our project we address interactions between soil fungi and bacteria in the degradation of pesticides.
Aims
The project aim to investigate the importance of interactions between fungi and bacteria in degradation of pesticides using the herbicides isoproturon and atrazin as model compounds.
Specific objectives are to investigate:
The degradation of isoproturon and atrazine by pure isolates of isolated fungi.
The degradation of the same pesticides by pure isolates of bacteria.
The synergistic action of these fungi and soil bacteria in the mineralisation of the pesticides.
The figure shows one scenario of interactions in the fate of a pesticide in soils. Fungal activity may lead to degradation products which can be further metabolised by bacteria, but also to "dead-end products" which are not degraded further.
Experiments
Experiments focusing on interactions between fungi and bacteria in degradation of pesticides.
Fungal degradation of isoproturon: Soil fungi from the three major taxonomic groups (zygo- asco- and basidiomycetes) are being isolated form agricultural soils. Their ability to transform isoproturon to different products (metabolites) is being evaluated in liquid media.
The mineralisation of metabolites produced by fungi in soil will be evaluated using microcosm-experiments. Soils will be added the relevant metabolites and the mineralisation will be monitored.
Co-culture studies with defined bacterial and fungal strains will be set up to determine if the fungal production of metabolites influence the subsequent degradation by bacterial cultures.
We employ high performance liquid chromatography and thin layer chromatography to identify and quantify the pesticides and their metabolites. Unknown metabolites are identified by mass spectrometry and NMR. Mineralisation is determined using radio labelled pesticides.
Fungal and bacterial activity in co-cultures will be monitored using denaturing gradient gel electrophoresis. DNA from co-cultures will be purified and quantified using specific primers for the different organism added. Their DNA can be separated on an gel and the size of the bands correspond to the amount of organisms present.
Publications
No publications yet
Congress contributions
Oral presentation by Stig Rønhede: Transformation of isoproturon by soil fungi. 4th International Symposium on Environmental Aspects of Pesticide Microbiology. "Pesticides, Microbial Functions and Biodiversity in Soils". Thessaloniki, Greece, September 5-9, 2004.
