Degradation of ioxynil to CO2 in soil |
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Authors: | JeMin C Hsu ND Camper |
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Institution: | 1. Department of Microbiology, Clemson University, Clemson, South Carolina 29631 USA;2. Department of Plant Pathology and Physiology, Clemson University, Clemson, South Carolina 29631 USA |
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Abstract: | Degradation of ioxynil (4-hydroxy-3,5-diiodobenzonitrile) to CO2 was detected in a clay loam, high organic matter content soil. The majority of radioactivity was recovered as 14CO2 from both ring-labeled and cyano-labeled ioxynil; however, 14CO2 was always released from cyano-labeled ioxynil at a much faster initial rate. No 14CO2 was released in treated sterile soil, either aerobically or anaerobically. Production of 14CO2 from cyanolabeled and ring-labeled ioxynil was greatly inhibited by HgCl2 (10?5M), and p-chloromercuribenzoate (5 × 10?5M), but slightly inhibited by ferricyanide (10?4M). No 14CO2 was evolved from ring-labeled ioxynil under anaerobic conditions. These observations indicated that the degradation of ioxynil to CO2 in soil was a microbial action and was oxygen dependent. This is consistent with the known mechanism of oxygenases in degrading benzene rings. Anaerobically, a small amount of 14CO2 was released from cyano-labeled ioxynil. Thin-layer chromatographic analyses of the culture supernatant revealed that 3,5-diiodo-4-hydroxybenzamide and 3,5-diiodo-4-hydroxybenzoic acid were intermediate metabolites. |
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