Isolation, identification and characteristics of a phoxim-degrading bacterium XSP-1

A bacteria strain XSP-1 capable of utilizing phoxim as sole carbon source was isolated from sludge collected from a pesticide manufacturer. It was preliminarily identified as Delftia sp. according to its physiological-biochemical analysis and the similarity analysis of its 16S rRNA gene sequence (GenBank Accession No. EF061135). Strain XSP-1 could degrade 100 mg/L phoxim within 7 h completely. The optimal pH and temperature for degradation were 7.0 and 35 degrees C respectively. The degrading rate showed a positive correlation to the initial inoculum size. Strain XSP-1 also showed good degrading performance against methyl parathion, chlorpyrifos and fenitrothion. PCR detection with degenerated primers designed according to the conserved sequences of reported mpd gene did not find target band, but it needs further study to verify whether strain XSP-1 harbors a new mpd gene.