Biodegradation of Diuron By Indigenous Soil Bacteria Isolated From Herbicide-contaminated Sites

Abstract

Residual herbicides are widely used in weed management; however, their persistence in the environment can lead to agronomic and ecological impacts. This study assessed bacterial isolates obtained from sugarcane soil with a history of diuron exposure for their ability to increase diuron dissipation under controlled conditions. Forty-two bacterial isolates were obtained, of which 18 tolerated the commercial formulation at 1,000 mg L −1 . In vitro assays identified isolates 7, 10, and 40 as the highest-performing isolates, with diuron reductions of 47.49%, 46.39%, and 43.86%, respectively. In autoclaved-soil microcosms, total diuron dissipation after 42 days reached 65.89%, 65.30%, and 65.81% for isolates 3, 7, and 35, respectively, compared with 52.91% in the uninoculated control; these values correspond to absolute increases of 12.98, 12.39, and 12.90 percentage points above the control. The estimated half-life decreased from 40.41 days in the control to 22.14, 22.60, and 22.29 days for isolates 3, 7, and 35, respectively. DCPMU (3-(3,4-dichlorophenyl)-1-methylurea) and DCA (3,4-dichloroaniline) were detected during incubation. The higher DCPMU levels are consistent with an initial N-demethylation step, whereas DCA was detected mainly at later sampling times and was not consistently increased by inoculation. Thus, the data support diuron transformation and increased dissipation but do not demonstrate complete degradation, mineralization, or detoxification. MALDI-TOF MS protein profiling provided provisional taxonomic matches for the selected isolates; no sequence-based confirmation was performed. The findings identify numbered isolates for further controlled evaluation, while sequence confirmation, biosafety assessment, metabolite-fate studies, and validation in non-sterile soil are required before any applied use.

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