Mercury bioremediation by engineered Pseudomonas putida KT2440 with adaptationally optimized biosecurity circuit

Hazardous materials, such as heavy metals, are the major sources of health risk. Using genetically modified organisms (GMOs) to dispose heavy metals has the advantages of strong environmental compatibility and high efficiency. However, the biosecurity of GMOs used in the environment is a major concern. In this study, a self-controlled genetic circuit was designed and carefully fine-tuned for programmable expression in Pseudomonas putida KT2440, which is a widely used strain for environmental bioremediation. The cell behaviours were controlled by automatically sensing the variation of Hg2+ concentration without any inducer requirement or manual interventions. More than 98% Hg2+ was adsorbed by the engineered strain with a high cell recovery rate of 96% from waterbody. The remaining cells were killed by the suicide module after the mission was accomplished. The escape frequency of the engineered P. putida strain was lower than 10(-9), which meets the recommendation of US NIH guideline for GMOs release (<10(-8)). The same performance was achieved in a model experiment by using natural lake water with addition of Hg2+. The microbial diversity analysis further confirmed that the remediation process made little impact on the indigenous ecosystem. Thus, this study provides a practical method for environmental remediation by using GMOs.

Automated summary

This study presents a practical method for environmental remediation using genetically modified organisms (GMOs). A self-controlled genetic circuit was designed and fine-tuned to programmably express in Pseudomonas putida KT2440, an extensively used strain for environmental bioremediation. The engineered strain exhibited high efficiency in adsorbing Hg2+ and had minimal impact on the indigenous ecosystem.