Transformation of the herbicide 2,6-dichlorobenzonitrile to the persistent metabolite 2,6-dichlorobenzamide (BAM) by soil bacteria known to harbour nitrile hydratase or nitrilase.
In soil the herbicide 2,6-dichlorobenzonitrile (dichlobenil) is degraded to the persistent metabolite 2,6-dichlorobenzamide (BAM) which has been detected in 19% of samples taken from Danish groundwater. We tested if common soil bacteria harbouring nitrile-degrading enzymes, nitrile hydratases or nitrilases, were able to degrade dichlobenil in vitro. We showed that several strains degraded dichlobenil stoichiometrically to BAM in 1.5-6.0 days; formation of the amide intermediate thus showed nitrile hydratase rather than nitrilase activity, which would result in formation of 2,6-dichlorobenzoic acid. The non-halogenated analogue benzonitrile was also degraded, but here the benzamide intermediate accumulated only transiently showing nitrile hydratase followed by amidase activity. We conclude that a potential for dichlobenil degradation to BAM is found commonly in soil bacteria, whereas further degradation of the BAM intermediate could not be demonstrated.
Department of Geochemistry, Geological Survey of Denmark and Greenland, 1350, Copenhagen, Denmark, msh@geus.dk
Maria Sommer
MS
Holtze
Jan
J
Sørensen
Hans Christian B
HC
Hansen
Jens
J
Aamand
D000619:Aminohydrolases / Q000378:metabolism*; D000643:Ammonium Chloride / Q000494:pharmacology; D001549:Benzamides / Q000378:metabolism; D001673:Biodegradation, Environmental; D006540:Herbicides / Q000378:metabolism*; D006836:Hydro-Lyases / Q000378:metabolism*; D009570:Nitriles / Q000378:metabolism*; D009584:Nitrogen / Q000494:pharmacology; D011549:Pseudomonas / Q000201:enzymology* / Q000378:metabolism; D012231:Rhizobium / Q000201:enzymology* / Q000378:metabolism; D012240:Rhodococcus / Q000201:enzymology* / Q000378:metabolism; D012988:Soil Microbiology
D001549:Benzamides; D006540:Herbicides; D009570:Nitriles; D000643:Ammonium Chloride; C057454:2,6-dichlorobenzamide; D000619:Aminohydrolases; C021867:nitrilase; D006836:Hydro-Lyases; C048831:nitrile hydratase; C055869:dichlobanil; D009584:Nitrogen