Degradation of chlorpyrifos and other pesticides by isolated bacteria under aerobic and anaerobic conditions

Chlorpyrifos is a widely used pesticide worldwide, and its residues are commonly found in water, soil, sediments, and fruits. This study isolated two mixed pure cultures of chlorpyrifos-degrading bacteria. Mixture 1 included Bacillus subtilis CP1 and Cupriavidus sp. CP2 isolated from soil, which degraded under aerobic conditions. Mixture 2 consisted of Pseudomonas aeruginosa CP3, Bacteroides sp. CP4, and Dehalococcoides mccartyi CP5 isolated from sediment degrading chlorpyrifos under anaerobic conditions. The mixed cultures 1 and 2 completely utilized the insecticide at 50 mg/L as a sole carbon source within 2 and 5 days, respectively. Moreover, mixed culture 1 could utilize 3,5,6-trichloro-2-pyridinol as a sole carbon and nitrogen source. During the degradation of chlorpyrifos, two metabolites, 3,5,6-trichloro-2-pyridinol and di-ethylthiophosphate, were produced by both mixed cultures. 5,6-Dihydro-2(1H)-pyridinone and 3,6-dihydroxypyridine-2,5-dione were also metabolites during the degradation by Bacillus subtilis CP1 and Cupriavidus CP2, respectively. Meanwhile, 5,6-dichloro-2-pyridinol, 2-pyridinol and fumaric acid were produced during the degradation by the mixed culture 2. The In vitro degradation of pesticides in collected soil and sediment enhanced with the inoculation of target degrading bacteria under both aerobic and anaerobic conditions. This study elucidates the mechanism of chlorpyrifos degradation by two bacterial mixtures, and the differences between in vitro and ex situ degradation.