Development of a broad-spectrum fluorescent heavy metal bacterial biosensor
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Bacterial biosensors can measure pollution in terms of their actual toxicity to living organisms. A recombinant bacterial biosensor has been constructed that is known to respond to toxic levels of Zn2+, Cd2+ and Hg2+. The zinc regulatory gene zntR and zntA promoter from znt operon of E. coli have been used to trigger the expression of GFP reporter protein at toxic levels of these ions. The sensor was induced with 3–800 ppm of Zn2+, 0.005–4 ppm of Cd2+ and 0.001–0.12 ppm of Hg2+ ions. Induction studies were also performed in liquid media to quantify GFP fluorescence using fluorimeter. To determine the optimum culture conditions three different incubation periods (16, 20 and 24 h) were followed. Results showed an increased and consistent fluorescence in cells incubated for 16 h. Maximum induction for Zn2+, Cd2+ and Hg2+ was observed at 20, 0.005 and 0.002 ppm, respectively. The pPROBE-zntR-zntA biosensor reported here can be employed as a primary screening technique for aquatic heavy metal pollution.
KeywordsBacterial biosensor Heavy metals Zinc Cadmium Mercury GFP
The authors would like to acknowledge Dr. W. S. Lakra, Director, CIFE and Dr. Dilip Kumar, Former Director, CIFE for providing necessary facilities, ICAR for JRF fellowship to the first author, Dr. Kshitish Majumdar and Dr. S. Ayyappan for their valuable help, advice and support.
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