Copy number of ArsR reporter plasmid determines its arsenite response and metal specificity
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The key component in bacteria-based biosensors is a transcriptional reporter employed to monitor induction or repression of a reporter gene corresponding to environmental change. In this study, we made a series of reporters in order to achieve highly sensitive detection of arsenite. From these reporters, two biosensors were developed by transformation of Escherichia coli DH5α with pLHPars9 and pLLPars9, consisting of either a high or low copy number plasmid, along with common elements of ArsR-luciferase fusion and addition of two binding sequences, one each from E. coli and Acidithiobacillus ferrooxidans chromosome, in front of the R773 ArsR operon. Both of them were highly sensitive to arsenite, with a low detection limit of 0.04 μM arsenite (~ 5 μg/L). They showed a wide dynamic range of detection up to 50 μM using high copy number pLHPars9 and 100 μM using low copy number pLLPars9. Significantly, they differ in metal specificity, pLLPars9 more specific to arsenite, while pLHPars9 to both arsenite and antimonite. The only difference between pLHPars9 and pLLPars9 is their copy numbers of plasmid and corresponding ratios of ArsR to its binding promoter/operator sequence. Therefore, we propose a working model in which DNA bound-ArsR is different from its free form in metal specificity.
KeywordsArsR Biosensors pLHPars9 and pLLPars9 plasmid Metal specificity
This work was supported by the High-level Leading Talent Introduction Program of GDAS (2016GDASRC-0208) and the Science and Technology Planning Project of Guangzhou City (201707020021) to XL, the National Natural Science Foundation of China (31600077) and the China Postdoctoral Science Foundation Grant (2017M612622) to YF, and the Science and Technology Project of Guangdong Province (2016B070701017) to MX.
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Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals.
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