Construction and characterization of Escherichia coli genetically engineered for bioremediation of Hg(2+)-contaminated environments

Abstract

Escherichia coli strains were genetically engineered to express an Hg 2؉ transport system and metallothionein. Overexpression of a glutathione S-transferase fusion protein of Saccharomyces cerevisiae or pea metallothionein significantly increased the bioaccumulation of Hg 2؉ transported by MerT and MerP and protected the cells from the accumulated Hg 2؉. The recombinant strains have excellent properties for bioremediation of Hg 2؉-contaminated environments.

Enhanced bioaccumulation of heavy metals by bacterial cells displaying synthetic phytochelatins

“…This phenomenon may be attributed to the limitation in Cd 2+ uptake resulting in most of the cysteine binding sites being either vacant or oxidized. A similar limitation in mercury transport has recently been demonstrated (Chen and Wilson, 1997). The coexpression of mercury transport proteins greatly improved mercury accumulation by cells overexpressing MTs intracellularly.…”

“…Overexpression of MTs in bacterial cells results in enhanced metal accumulation and thus offers a promising strategy for the development of microbial-based biosorbents to remediate metal contamination (Kille et al, 1991;Pazirandeh et al, 1995;Romeyer et al, 1990). However, metal removal by intracellular MTs has been problematic because of the limited metal uptake (Chen and Wilson, 1997) and the inability to recycle intracellularly accumulated metals (Gadd and White, 1993). One clever solution to bypass this problem is to express MTs on the cell surface.…”

Bacterial mercury resistance from atoms to ecosystems

“…Constitutive mer operons were prepared [278] with the prospect of improving wastewater treatment operations [279], but when tested they proved inferior to naturally isolated mercury-reducing strains [272]. The construction of recombinant E. coli with enhanced mercury accumulation due to combined merTP and cytoplasmic eukaryotic metallothioneins was reported [280]. Induced cells in hollow-¢ber bioreactor retained 99% of the mercury from wastewater containing s 2 mg l 31 mercury, various other ions, and at an alkaline pH.…”

Construction and expression of functional multi-domain polypeptides in Escherichia coli: expression of the Neurospora crassa metallothionein gene

“…The construction of genetically engineered organisms for heavy metal bioaccumulation has recently been reported by other investigators. Chen and Wilson (1997) recently reported the simultaneous expression of a metallothionein gene and a mercury transport system in E. coli. Sousa et al (1996Sousa et al ( , 1998 have also reported the expression of yeast and mammalian metallothioneins as well as a poly histidine motif within the outer membrane of E. coli using the lamB as an anchoring domain.…”

“…The use of genetic engineering to increase the affinity and biosorptive capacity of bacterial cells for heavy metals is a promising area of research for the development of bacterial-based biosorbents. The expression and cellular targeting of high affinity metal-binding proteins such as metallothioneins or de novo metal-binding peptides to increase bacterial heavy metal binding has been reported by several groups (Berka et al 1988;Pazirandeh et al 1995Pazirandeh et al , 1998Sousa et al 1996Sousa et al , 1998Chen and Wilson 1997). Bacterial cells properly expressing and localizing these proteins outside the cytosol have demonstrated enhanced bioaccumulation of target metals.…”