Abstract
The development of genetic engineering, especially synthetic biology, greatly contributes to the development of novel metal biosensors. The cad operon encoding cadmium resistance was previously characterized from Pseudomonas putida. In this study, single-, dual-, and triple-signal output Cd(II) biosensors were successfully developed using artificial translationally coupled cad operons. Sensitivity, selectivity, and response toward Cd(II) and Hg(II), of three biosensors were all determined. Reporter signals of three biosensors all increased within the range 0.1–3.125 μM Cd(II). Three biosensors responded strongly to Cd(II), and weakly to Hg(II). However, the detection ranges of Cd(II) and Hg(II) do not overlap in all three biosensors. Next, novel Cd(II) biosensing coupled with bioadsorptive artificial cad operons were assembled for the first time. Cd(II)-induced fluorescence emission, enzymatic indication, and Cd(II) binding protein surface display can be achieved simultaneously. This study provides an example of one way to realize multiple signal outputs and bioadsorption based on the redesigned heavy metal resistance operons, which may be a potential strategy for biodetection and removal of toxic metal in the environment, facilitating the study of the mechanism and dynamics of bioremediation.
Highlights
Widespread distribution of heavy metals mostly results from human industrial and agricultural activities, and the presence of toxic heavy metals exerts adverse effects on the environment as well as on human health (WHO, 2010)
Some toxic heavy metals such as lead, mercury, and cadmium have been associated with human health concerns at the microgram level in food and drinking water (Rehman et al, 2018)
This study provides an example of one way to realize fluorescent signal output, enzymatic signal output, and even bioadsorption simultaneously based on the artificial MerR family operons upon target heavy metal exposure
Summary
Widespread distribution of heavy metals mostly results from human industrial and agricultural activities, and the presence of toxic heavy metals exerts adverse effects on the environment as well as on human health (WHO, 2010). Some toxic heavy metals such as lead, mercury, and cadmium have been associated with human health concerns at the microgram level in food and drinking water (Rehman et al, 2018). The advantages of traditional instrumental analysis for cadmium such as atomic absorption spectroscopy and inductively coupled plasma mass spectrometry are accuracy and sensitivity (Wanekaya et al, 2008). These analytic methods are costly and time-consuming.
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