Mercury resistance and accumulation in Escherichia coli with cell surface expression of fish metallothionein
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Recombinant tilapia (Oreochromis mossambicus) fish metallothionein (MT) was used as a surface biosorbent for mercury removal in Escherichia coli. Fish MT conferred better resistance than did mouse or human MT. When tilapia MT (tMT) was fused with an outer-membrane protein, outer membrane protein C (OmpC), the membrane-targeted fusion protein, OmpC–tMT, gave enhanced resistance compared with cytoplasmic tMT expressed in the same host cell. The cytoplasmically expressed tMT showed high mercury adsorption (4.3 ± 0.4 mg/g cell dry weight). The cell surface that expressed E. coli showed about 25% higher adsorption ability (5.6 ± 0.4 mg/g) than the cells expressing cytoplasmic MT, attaining almost twice the level of adsorption of the control plasmid (3.0 ± 0.4 mg/g). As MTs are also known for their ability to scavenge hydroxyl-free radicals, it was also shown that tMT exhibited better radical-scavenging activities than glutathione. These results suggest that fish MT has potential for the development of a bioremediation system for mercury removal that protects the harboring E. coli host by free-radical scavenging.
KeywordsMetallothionein Mercury Bioadsorption OmpC Tilapia
We thank Professor Jo-Shu Chang (National Cheng Kung University, Taiwan) for his kind gift of the pMAL-p2X-MT1A and pMBP-TEV-MT1 plasmids containing human MT1A and mouse MT1 cDNA. We also thank Prof. Su-Mei Wu (National Chia Yi University, Taiwan) for antibody of the rabbit anti-tMT IgG. This work was supported by the grants (NSC 96-3114-P-001-004-Y and NSC 97-3114-P-001-001) from the National Science Council, Taiwan, People’s Republic of China.
- Allen P (1994) Mercury accumulation profiles and their modification by interaction with cadmium and lead in the soft tissues of the cichlid Oreochromis aureus during chronic exposure. Bull Environ Contam Toxicol 53:684–692Google Scholar
- Brand-Williams W, Cuvelier ME, Berset C (1995) Use of a free radical method to evaluate antioxidant activity. Food Sci Technol Res 28:25–30Google Scholar
- Chen S, Wilson DB (1997a) Construction and characterization of Escherichia coli genetically engineered for bioremediation of Hg(2+)-contaminated environments. Appl Environ Microbiol 63:2442–2445Google Scholar
- Kao WC, Chiu YP, Chang CC, Chang JS (2006) Localization effect on the metal biosorption capability of recombinant mammalian and fish metallothioneins in Escherichia coli. Biotechnol Prog 22:1256–1264Google Scholar
- Sousa C, Kotrba P, Ruml T, Cebolla A, De Lorenzo V (1998) Metalloadsorption by Escherichia coli cells displaying yeast and mammalian metallothioneins anchored to the outer membrane protein LamB. J Bacteriol 180:2280–2284Google Scholar
- Valls M, de Lorenzo V (2002) Exploiting the genetic and biochemical capacities of bacteria for the remediation of heavy metal pollution. FEMS Microbiol Rev 26:327–338Google Scholar
- Xu Z, Lee SY (1999) Display of polyhistidine peptides on the Escherichia coli cell surface by using outer membrane protein C as an anchoring motif. Appl Environ Microbiol 65:5142–5147Google Scholar