Organophosphate degrading Pseudomonas putida isolated from agricultural soil

Abstract

Bacteria capable of degradation organopdosphorus nematicide (cadusafos) in soil were isolated by enrichment culture technique. Bacterial isolates were characterized by biochemical methods, and molecular methods such as restriction fragment length polymorphism (RFLP) patterns of the 16S rRNA gene and partial 16S rRNA gene sequence analysis. Five cadusafos-degrading isolates were identified as strains of Pseudomonas putida PC1, PC3, PC5, PC7 and PC10. The isolate PC7 showed the highest ability to degrade cadusafos and consequently was selected for further analysis. Cadusafos degradation by PC7 was most rapid at 25 and 37 °C, and at a slow rate at 10 °C. Degrading ability of PC7 was slower in the presence of succinate or glucose. Moreover, when the cadusafos was supplied as a sole source of phosphorus, the degrading ability of PC7 was also slower. Only 2 × 10 3 cfu ml −1 as initial inoculum of strain PC7 was capable of degrading cadusafos while 2 × 10 10 cfu ml −1 degraded cadusafos completely in 2 days. Cadusafos was degraded rapidly by PC7 in MSMN at pHs ranging from 6 to 7.5, but not at pH 5.7. Isolate PC7 efficiently removed cadusafos from only sterilized soil at low inoculum density but removed it from both sterilized and natural soil when presented at high inoculum density. Moreover, other organophosphorus nematicides tested such as ethoprophos, fenamiphos, isofenphos and isazofos were degraded by PC7 but at slow rate. Such bacteria that use nematicides as a carbon source could be used in bioremediation of environment contaminated with pesticide waste.