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

The 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 mu g 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 mu g ml(-1). The dissipation of NS (40 mu g 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 mu g 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, especially in the presence of the isolate. Overall, this study proves Pseudomonas aeruginosa B9 as a suitable candidate for bioremediation of NS in contaminated sites.