Study on the Atrazine-degrading Genes in Arthrobacter sp. AG1

Atrazine could be used as the sole carbon, nitrogen and energy source necessary for growth, by strain Arthrobacter sp. AG1, and the atrazine-degrading genes of AG1 were found to be a combination of trzN, atzB and atzC. The atrazine chloride hydrolysase gene trzN was cloned by PCR amplification, whose sequence shared 99% identity with that of Norcardioides sp. C190. Two large plasmids were found in AG1, trzN and atzB were confirmed to be localized on the larger plasmid pAG1 by the method of southern hybridization. Subculturing of AG1 in liquid LB for three generations resulted in the loss of degrading activity in 34% of the subsequent cells; however, none of the plasmid was lost. PCR amplification results showed that the mutants had only lost the trzN gene instead of atzB and atzC. It was deduced that mutation might be because of the trzN gene deletion from the plasmid pAG1. This study provided new evidence that atrazine metabolic genotypes resulted from horizontal gene transfer between different bacteria under selective environmental pressure.