ISOLATION, IDENTIFICATION OF NOVEL ATRAZINE-DEGRADING BURKHOLDERIA SP. AND ITS ATRAZINE BIODEGRADATION EFFICIENCYSOPID SAWANGJITAbstract In this study, five sugarcane field soils with a long history of atrazine application in Kanchanaburi, Nakhon Pathom and Ratchaburi provinces have been explored for their potential of atrazine biodegradation. For the atrazine degrading bacteria isolation, the soils used in this study named KB1, KB2, KB3, NP1 and RB1 were inoculated in MS medium containing atrazine. Five gram-negative bacterial strains, which were able to use this herbicide as a sole source of nitrogen were isolated. Based on physiological and 16S rRNA gene nucleotide sequence analysis, all five isolated bacteria were identified as Burkholderia sp. with 92.4-99.8% nucleotide identity. The bacterial isolates characterized in this study are named Burkholderia sp. AKB1, Burkholderia sp. AKB2, Burkholderia sp. AKB3, Burkholderia sp. ANP1 and Burkholderia sp. ARB1. The Thai isolates bacteria showed high atrazine-mineralizing efficiency, ranging from 91.38-96.27% (from 300 ppm.) and 50-95.04% (from 40 mg/kg) in liquid cultures after 21 days and soil after 4 week, respectively. When atrazine was mineralized by the consortium, two metabolites, DEA and DIA were not detected. These results indicated that atrazine was degraded via hydrolytic dechlorination.
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