Exogenous Zn²⁺ enhance the biodegradation of atrazine by regulating the chlorohydrolase gene trzN transcription and membrane permeability of the degrader Arthrobacter sp. DNS10

Enhancing the biodegradation efficiency of atrazine, a kind of commonly applied herbicide, has been attracted much more concern. Here, Zn²⁺ which has long been considered essential in adjusting cell physiological status was selected to investigate its role on the biodegradation of atrazine by Arthrobacter sp. DNS10 as well as the transmembrane transport of atrazine during the biodegradation period. The results of gas chromatography showed that the atrazine removal percentages (initial concentration was 100 mg L^-1) in 0.05 mM Zn²⁺ and 1.0 mM Zn²⁺ treatments were 94.42% and 86.02% respectively at 48 h, while there was also 66.43% of atrazine left in the treatment without exogenous Zn²⁺ existence. The expression of atrazine chlorohydrolase gene trzN in the strain DNS10 cultured with 0.05 mM and 1.0 mM Zn²⁺ was 7.30- and 4.67- times respectively compared with that of the non-zinc treatment. In addition, the flow cytometry test suggests that 0.05 mM of Zn²⁺ could better adjust the membrane permeability of strain DNS10, meanwhile, the amount of atrazine accumulation in the strain DNS10 co-cultured with this level Zn²⁺ was 2.21 times of that of the strain without Zn²⁺. This study may facilitate a better understanding of the mechanisms that exogenous Zn²⁺ enhances the biodegradation of atrazine by Arthrobacter sp. DNS10.