Isolation of monocrotophos-degrading strain Sphingobium sp. YW16 and cloning of its Tn opdA

The bacterial strain Sphingobium sp. YW16, which is capable of degrading monocrotophos, was isolated from paddy soil in China. Strain YW16 could hydrolyze monocrotophos to dimethylphosphate and N-methylacetoacetamide and utilize dimethylphosphate as the sole carbon source but could not utilize N-methylacetoacetamide. Strain YW16 also had the ability to hydrolyze other organophosphate pesticides. A fragment (7067 bp) that included the organophosphorus hydrolase gene, opdA, was acquired from strain YW16 using the shotgun technique combined with SEFA-PCR. Its sequence illustrated that opdA was included in TnopdA, which consisted of a transpose gene, a putative integrase gene, a putative ATP-binding protein gene, and opdA. Additionally, a conjugal transfer protein gene, traI, was located downstream of TnopdA. The juxtaposition of TnopdA with TraI suggests that opdA may be transferred from strain YW16 to other bacteria through conjugation. OpdA was able to hydrolyze a wide range of organophosphate pesticides, with the hydrolysis efficiency decreasing as follows: methyl parathion > fenitrothion > phoxim > dichlorvos > ethyl parathion > trichlorfon > triazophos > chlorpyrifos > monocrotophos > diazinon. This work provides the first report of opdA in the genus Sphingobium.