Submitted to: American Society for Microbiology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 5/23/2010
Publication Date: 5/23/2010
Citation: Munoz, A.M., Koskinen, W.C., Sadowsky, M.J. 2010. Biodegradation of Metolachlor by Soil Bacteria and Yeast [abstract]. American Society for Microbiology. Q-2834/867. Interpretive Summary:
Technical Abstract: Metolachlor (2-chloro-6’-ethyl-N-(2-methoxy-1-methylethyl) aceto-o-toluidide) is a pre-emergent chloroacetanilide herbicide used to control broadleaf and annual grassy weeds of corn, soybean, peanuts, sorghum, potatoes, cotton, and woody ornamental plants. It has been estimated that 15-24 and 20-24 million pounds of metolachlor and s-metolachlor, respectively, were used in the U.S. in 2001. The S enantiomer of metolachlor, s-metolachlor, is the most effective form for weed control. While the degradation of metolachlor in soils is thought to occur primarily by microbial activity, little is known about the microorganisms that carry out this process and the mechanisms by which this occurs. In this study we examined a silty-clay soil from Spain (a Luvisol) with a 10 and 2 year history of metolachlor and s-metolachlor application, respectively, for microorganisms that had the ability to degrade this herbicide. We report here on the isolation and characterization of pure cultures of Debaromyces hansenii and Bacillus simplex that have the ability to use metolachlor as a sole source of carbon for growth. Species assignment was confirmed by morphological and biochemical criteria and by sequence analysis of 18S and 16S rRNA, respectively. HLPC and LC-MS analyses indicated that Bacillus simplex degraded 40% of metolachlor following 5 days of growth in minimal medium, and Candida Xestobii degraded 50% after 4 days of growth. Results of these studies indicate that microorganism comprising two main branches of the tree of life have acquired the ability to degrade the same novel chlorinated herbicides that have recently been added to the biosphere.