Affiliation:
1. Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
Abstract
ABSTRACT
2,6-Dichlorobenzamide (BAM), a persistent metabolite from the herbicide 2,6-dichlorobenzonitrile (dichlobenil), is the pesticide residue most frequently detected in Danish groundwater. A BAM-mineralizing bacterial community was enriched from dichlobenil-treated soil sampled from the courtyard of a former plant nursery. A BAM-mineralizing bacterium (designated strain MSH1) was cultivated and identified by 16S rRNA gene sequencing and fatty acid analysis as being closely related to members of the genus
Aminobacter
, including the only cultured BAM degrader,
Aminobacter
sp. strain ASI1. Strain MSH1 mineralized 15 to 64% of the added [
ring
-U-
14
C]BAM to
14
CO
2
with BAM at initial concentrations in the range of 7.9 nM to 263.1 μM provided as the sole carbon, nitrogen, and energy source. A quantitative enzyme-linked immunoassay analysis with antibodies against BAM revealed residue concentrations of 0.35 to 18.05 nM BAM following incubation for 10 days, corresponding to a BAM depletion of 95.6 to 99.9%. In contrast to the
Aminobacter
sp. strain ASI1, strain MSH1 also mineralized the herbicide itself along with several metabolites, including
ortho
-chlorobenzonitrile,
ortho
-chlorobenzoic acid, and benzonitrile, making it the first known dichlobenil-mineralizing bacterium.
Aminobacter
type strains not previously exposed to dichlobenil or BAM were capable of degrading nonchlorinated structural analogs. Combined, these results suggest that closely related
Aminobacter
strains may have a selective advantage in BAM-contaminated environments, since they are able to use this metabolite or structurally related compounds as a carbon and nitrogen source.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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