Isolation and identification of paraquat degrading Bacteria from Tabriz soils

Paraquat is a herbicide which frequently used in agricultural systems for weeds control. Paraquat, relatively with long half-life, forms strong bonds with soil particles and persists in soil for a long time as a pollutant. Recently, various methods have been proposed for the removal or reduction of pesticides from soils. Bioremediation is an environmental friendly approach to remove pesticides from soil. In this study, soil samples collected from arable lands of Tabriz, East Azarbaijan province, Iran. The experiment was performed in a factorial completely randomized design with three replications. Five levels of Paraquat (0, 25, 50, 75 and 100 mg. L-1) in the presence or absence of glucose (%1 w/v) in liquid mineral salts medium (MSM) were inoculated with some bacterial isolates under in vitro conditions. After 30 days of incubation at 26 °C, the residual amount of Paraquat was spectrophotometrically determined at wavelength of 396 nm. Two efficient isolates subjected to the biochemical tests and 16S rRNA sequencing for identification purpose. The isolates identified, as Achromobacterxylosoxidans andStreptomyces sp. The amount of Paraquat degradation for those isolates in 50 mg. L-1 treatment without glucose were 47 and 40.667% and with glucose were 74.333 and 70.267%, respectively. Paraquat biodegradation increased significantly in the presence of both bacterial isolates compared to control treatment. Paraquat biodegradation increased considerably in the presence of glucose as a readily available energy source by both bacterial isolates.