dissipation of butachlor by a new strain of pseudomonas sp. isolated from paddy soils

Butachlor (but) is a chloroacetanilide herbicide widely applied to rice paddies to control annual grass and broad-leaf weeds. a but-degrading bacterial strain (pk) was isolated from paddy soils. biochemical and 16s rrna sequencing characteristics confirmed the strain as pseudomonas aeruginosa (99% resemblance). the isolate dissipated but (100 μg/ml) in an m9 liquid medium with a rate of 0.5 ± 0.03 day^-1 and dt50 and dt90 of 1.38 ± 0.10 days and 4.58 ± 0.32 days, respectively. soil dissipation of but was investigated under flooded conditions. in sterile soils, the isolate increased the dissipation of but (200 μg/g) (dt50 = 12.38 ± 1.83 days, dt90 = 41.12 ± 6.09 days, k = 0.06 ± 0.01 day-1) compared to sterile non-inoculated samples (dt50 = 26.87 ± 2.82 days, dt90 = 89.25 ± 9.36 days, k = 0.03 ± 0.00 day^-1). in non-inoculated non-sterile soil experiments, the dissipation of but was faster (dt50 = 15.17 ± 2.11 days, dt90 = 50.38 ± 7.02 days, k = 0.05 ± 0.00 day^-1) compared to non-inoculated sterile ones, and inoculating the isolate accelerated the removal of but in non-sterile soils significantly (dt50 = 8.03 ± 1.20 days, dt90 = 26.68 ± 3.97 days, k = 0.09 ± 0.01 day^-1). but inhibited soil respiration (sr) initially for 5 days, followed by an increase until day 20. the increase in sr was more pronounced in the co-presence of but and the isolate. the results of this research suggest p. aeruginosa pk as a suitable candidate for but bioremediation.