Use of cop operon of Staphylococcus epidermidis TWSL_17 in biosensor construction

Abstract

Heavy metals are defined as metallic elements, which have a relatively higher density than water. Copper is an abundant metal element in the environment which is required by all living organisms. However, high concentration of copper can be toxic to both prokaryotes and eukaryotes. Bioremediation is widely used in heavy metal remediation where resistant mechanisms of microbes are mainly used. Staphylococcus epidermidis TWSL_17 was found to be resistant to heavy metals such as Cu, Zn, Pb and Cd. This study was aimed at using proteins involved in metal resistance to develop a bacterial biosensor to detect metal contaminations in wastewater. The cop operon involved in copper homeostasis, consists of promoter Pcop, regulator csoR, PIB-ATPase copA, and copper chaperone copZ in Staphylococcus sp. A whole-cell biosensor was designed using the cop operon of TWSL_17 and a reporter, GFP. Pcop and csoR were PCR amplified using gDNA of TWSL_17. The resulted PCR amplicon of 397 bp was then digested using NheI and XbaI and ligated with the expression vector, pQBI-T7-GFP. Subsequently transformed into E. coli BL21 (DE3) cells and screened using colony PCR. Metal sensitivity of the recombinant was evaluated using Cu2+, Zn2+, and Ni2+. A significant difference of bacterial growth in the presence of Zn2+ was observed while a significant difference of bacterial growth was not observed in the presence of Cu2+ and Ni2+. However, constructed whole-cell biosensor did not fluoresce in the presence of any heavy metals.