Molecular identification and resistance investigation of atrazine degrading bacteria in the sediments of Karun River, Ahvaz, Iran

Nowadays, the use of pesticides as plant protection products has become widely prevalent, leading to the entry of large amounts of pesticides into soil and water resources, and subsequently, a threat to the environment. The objective of this study was molecular identification and resistance investigation of atrazine degrading bacteria in the sediments of Karun River, Ahvaz, Iran. Nine samples were collected in both summer (Jul) and autumn (Nov) year 2012 from a depth of 3 to 5 cm of the sediments. Atrazine degrading bacteria were enriched in a culture containing atrazine with initial concentration of 30 mg/L. Identification of isolated bacteria was performed by morphological and biochemical test and molecular analysis based on 16S rDNA sequencing. The atrazine biodegradation rate was obtained by high-performance liquid chromatography (HPLC). Six strains was identified including Achromobacter insolitus strain F-N3, Delftia tsuruhatensis strain F-N4, Klebsiella pneumonia F-N1, Enterobacter ludwigii strain F-N5, Serratia marcescens strain F-N6 in both summer and autumn, and Exiguobacterium profundum strain F-N2 only in the summer. The minimum inhibitory concentration (MIC) of atrazine showed that the most resistant species belonged to E. ludwigii F-N5 and D. tsuruhatensis F-N4 in the both seasons. The atrazine degradation rates of the two strains reached 90 and 85%, respectively after 7 days culture. Result showed that indigenous bacteria in the Karun River can degrade the atrazine effectively.