Potential Whole-Cell Biosensors for Detection of Metal Using MerR Family Proteins from Enterobacter sp. YSU and Stenotrophomonas maltophilia OR02

Abstract

Cell-based biosensors harness a cell’s ability to respond to the environment by repurposing its sensing mechanisms. MerR family proteins are activator/repressor switches that regulate the expression of bacterial metal resistance genes and have been used in metal biosensors. Upon metal binding, a conformational change switches gene expression from off to on. The genomes of the multimetal resistant bacterial strains, Stenotrophomonas maltophilia Oak Ridge strain 02 (S. maltophilia 02) and Enterobacter sp. YSU, were recently sequenced. Sequence analysis and gene cloning identified three mercury resistance operons and three MerR switches in these strains. Transposon mutagenesis and sequence analysis identified Enterobacter sp. YSU zinc and copper resistance operons, which appear to be regulated by the protein switches, ZntR and CueR, respectively. Sequence analysis and reverse transcriptase polymerase chain reaction (RT-PCR) showed that a CueR switch appears to activate a S. maltophilia 02 copper transport gene in the presence of CuSO4 and HAuCl4·3H2O. In previous studies, genetic engineering replaced metal resistance genes with the reporter genes for β-galactosidase, luciferase or the green fluorescence protein (GFP). These produce a color change of a reagent, produce light, or fluoresce in the presence of ultraviolet (UV) light, respectively. Coupling these discovered operons with reporter genes has the potential to create whole-cell biosensors for HgCl2, ZnCl2, CuSO4 and HAuCl4·3H2O.

Draft genome analysis for Enterobacter kobei, a promising lead bioremediation bacterium

“…Not only zinc but also lead and cadmium greatly increased the expression of zntA , in a process uncontrolled and mediated through zntR ( Binet and Poole, 2000 ). zntR and zntA genes were located at different locations on the chromosome ( Baya et al, 2021 ). This confirms our findings about the lead resistance of E. kobei FACU6.…”

Draft genome of Raoultella planticola, a high lead resistance bacterium from industrial wastewater

“…zntA is significantly induced by lead and cadmium not by zinc only, its expression is uprgulated and is mediated by zntR (Binet and Poole 2000 ). z ntR and zntA genes are not adjacent to each other but are located on different locations of the chromosome (Baya et al 2021 ). So, this supports our results of R. planticola FACU 3’s ability to resist lead.…”

“…It is worth noting that the presence of quinone reductase gene ( chrR ) helps in reducing of chromate thus in chromate bioremediation (Eswaramoorthy et al 2012 ; Paul et al 2020 ). There are gene systems/gene cluster encoded for copper hemostasis like cop operon, cutC, cue O and cue R in addition to cus operon and pco/sil operon which participates in silver efflux system (Franke et al 2003 ; Gudipaty et al 2012 ) and found on the chromosome as several studies reported that these genes are regularly be located on the chromosome of Enterobacteriaceae species not restricted to plasmid (Baya et al 2021 ). The presence of mer R which is a transcriptional regulator for mercury resistance may be evidence of R. planticola FACU 3 may be mercury resistant bacteria (Brown et al 2003 ).…”