Green fluorescent protein based whole cell bacterial biosensor for the detection of bioavailable heavy metals in soil environment

A Green fluorescent protein (GFP) based whole cell bacterial biosensor was prepared using a bacterial strain sensitive to several heavy metals in order to detect bioavailable heavy metals in soils. The transformant, named as Bacillus megaterium VR1 was immobi-lized in silica matrix using sol-gel technology, and optimized for its effective pH range, cell density, exposure time, and storage stability. The lowest detection limit (LOD) for each metal was also determined. The pH range for the bacterial strain was found to be between pH 5-8.5. The optimum exposure time for the transformed bacterial strain to respond to the lowest tested concentration of heavy metal at 25% of inhibition compared to the control was determined as 4 h, 4 h, and 7 h, for Cd, Cu and Zn, respectively. SiNa/LUDOX 1/1 was selected as the optimum immobilization matrix. Storage up to 2 weeks did not show any reduction in the fluorescence in all the matrices. The linear range of the whole cell bacterial biosensor was determined as 0-10; 0-20 and 0-100 mg/L for Cd, Cu and Zn respectively. The lowest detection limit was determined as 1.42 x 10(-4), 3.16 x 10(-4), and 2.42 x 10(-4) mg/L for Cd, Cu and Zn, respectively. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A GFP-based whole cell bacterial biosensor was developed to detect bioavailable heavy metals in soils, using Bacillus megaterium VR1 strain immobilized in silica matrix. Optimal conditions such as pH range, exposure time, and storage stability were optimized, with lowest detection limits determined for each metal. Storage stability up to 2 weeks was shown, and linear ranges of detection were determined for Cd, Cu, and Zn.