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Journal of Cleaner Production
Volume 337, 2022, 130524

Mercury bioremediation in aquatic environment by genetically modified bacteria with self-controlled biosecurity circuit

Yubin Xuea, Pei Dub, Amal Amin Ibrahim Shendic, Bo Yuc,d

CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.

Abstract

Heavy metal pollution such as mercury (Hg2+) poses a severe threat to food security worldwide because of enrichment through food chain and, eventually, to the human body. Biological remediation approaches are promising, but in some cases, the natural microorganisms are not ideal for practical application, which requires genetic modification of such organisms. However, the threat of genetically modified bacteria being released into the environments has long been the major concern that limits the applications of such technologies. In this study, we designed and optimized a genetic circuit that is capable of activating a Hg2+ adsorption module after sensing Hg2+ in waterbody, and killing cells with a cell suicide module in a programmable manner. With this circuit, the engineered Escherichia coli cells are programmed to express Hg2+ adsorption protein only when Hg2+ concentration is above a certain threshold. Then, cells absorbed with Hg2+ can be removed from natural environments with magnetically immobilized strategy and the remaining cells are programmed to be killed by the suicide module when Hg2+ concentration drops below a threshold in waterbody. Importantly, the suicide module was carefully optimized to ensure the escape rate is below 10−9, which meets the recommendation demanded by U.S. NIH guideline. The absorption cells could be reused for 5 cycles, with an Hg2+ adsorption efficiency steadily above 95% and escape rates below 10−9. Thus, the advancement of this study sheds light on using engineered microbes directly in an open circumstance.

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