Cadmium resistance mechanism in Escherichia coli P4 and its potential use to bioremediate environmental cadmium

Abstract

A cadmium-resistant bacterium was isolated from industrial wastewater and identified as Escherichia coli (dubbed as P4) on the basis of morphological, biochemical tests and 16S rRNA ribotyping. It showed optimum growth at 30 °C and pH 7. E. coli P4 found to resist Cd(+2) (10.6 mM) as well as Zn(+2) (4.4 mM), Pb(+2) (17 mM), Cu(+2) (3.5 mM), Cr(+6) (4.4 mM), As(+2) (10.6 mM), and Hg(+2) (0.53 mM). It could remove 18.8, 37, and 56 % Cd(+2) from aqueous medium after 48, 96, and 144 h, respectively. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and Energy-dispersive X-ray (EDX) analysis also confirmed the biosorption of Cd(+2) by E. coli P4. However, temperature and pH were found to be the most critical factors in biosorption of Cd(+2) by E. coli P4. Cd(+2) stress altered E. coli P4 cell physiology analyzed by measuring glutathione (GSH) and non-protein thiol (cysteine) levels which were increased up to 130 and 48 %, respectively. Quantitative real-time polymerase chain reaction (qRT-PCR) showed alteration in the expression levels of ftsZ, mutS, clpB, ef-tu, and dnaK genes in the presence of Cd(+2). Total protein profiles of E. coli P4 in the absence and presence of Cd(+2) were compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), which showed remarkable difference in the banding pattern. czcB gene, a component of czcCBA operon, was amplified from genomic DNA which suggested the chromosomal-borne Cd(+2) resistance in E. coli P4. Furthermore, it harbors smtAB gene which plays a significant role in Cd(+2) resistance.

Characterization and Sorptivity of the Plesiomonas shigelloides Strain and Its Potential Use to Remove Cd2+ from Wastewater

“…The intensity of the bands varied in different regions after the interaction with Cd 2+ . These results are similar to the findings by Khan [23]. SEM results revealed that P. shigelloides H5 adapts to high concentrations of cadmium ions in the environment by increasing the volume, which is similar to findings by Wu and Sun [22].…”

“…Many indigenous species of microorganisms have the capacity to tolerate heavy metals, for example, Enterococcus faecalis, Escherichia coli, Bosea sp., and Bacillus catenulatus [12,[20][21][22][23]. However, mutations can occur in some microorganisms due to the contamination of heavy metals in the environment.…”

“…One previous study found that bacteria can transport metal ions into the cells by passive transport or by an outmembrane's Mn 2+ /Zn 2+ /Ca 2+ transporter [22]. The intracellular Cd 2+ can combine with phosphate to perform precipitate, or Cd 2+ toxicity can cause a cadmium efflux pump CzcCBA to efflux Cd 2+ in order to reduce damage [23]. In this study, it was found that living biomass can adsorb more cadmium ions than dried biomass and that some precipitates formed in P. shigelloides H5 after being cultured in Cd 2+ solution, which indicated that living biomass can absorb Cd 2+ in cells, but adsorption amounts were much lower than adsorption amounts (Figures 8 and 11).…”

Type 1 metallothionein (ZjMT) is responsible for heavy metal tolerance in Ziziphus jujuba

“…Biosorption of heavy metals using materials of microbial or plant origin has been considered as an innovative technology for removal of such pollutants [44]. For example, E. coli is biosorptive and has recently been used to adsorb heavy metals [45,46]. Enhanced uptake and bioaccumulation of mercury by E. coli have been achieved through genetic engineering to produce a recombinant strain [47].…”

An operon consisting of a P-type ATPase gene and a transcriptional regulator gene responsible for cadmium resistances in Bacillus vietamensis 151–6 and Bacillus marisflavi 151–25

“…The most prominent mechanism of resistance to Cd 2+ is the use of efflux pumps [17]. Several bacteria, such as Alcaligenes eutriphus [18], Staphylococcus aureus [19], Bacillus subtilis [20], Listeria monocytogenes [21] and Escherichia coli [22] have demonstrated resistance to Cd 2+ .…”