Degradation and Detoxification of Nicosulfuron by a Pseudomonas Strain Isolated from a Contaminated Cornfield Soil

ABSTRACTThe dissipation and detoxification of nicosulfuron (NS) by Pseudomonas aeruginosa B9 isolated from a cornfield soil was investigated. The fastest decline of NS occurred at 40 µg ml−1 in liquid media with 0.25% glucose plus 0.05% yeast extract (DT50 = 4 days) with a notable pH reduction (pH ˂ 5). Bioassay tests showed considerable phytotoxicity of NS for Cress (Lepidium sativum L.) with 50% shoot growth inhibition (SGI) at 40 µg ml−1. The dissipation of NS (40 µg ml−1) by the B9 isolate reduced the SGI significantly (SGI: up to 45 ± 3%) compared to the non-inoculated media (SGI: up to 58 ± 4%). In soils with the B9 isolate, NS dissipation, especially at 0.3 µg g−1, was faster with a more significant SGI reduction (k = 0.08 ± 0.00 day−1; SGI = 2 ± 1%) compared to non-inoculated samples (k = 0.03 ± 0.00 day−1; SGI = 8 ± 1%). NS initially inhibited soil respiration, microbial biomass carbon, and dehydrogenase activity. The effect was however transient, and these parameters recovered within 10 days, es...