title: Mercury resistance and accumulation in Escherichia coli with cell surface expression of fish metallothionein.
abstract: 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.
authors.affiliation: Department of Life Sciences, National Chung Hsing University, Taichung, 402, Taiwan.
authors.forename: Kuo-Hsing
authors.initials: KH
authors.lastname: Lin
authors.forename: Mei-Fang
authors.initials: MF
authors.lastname: Chien
authors.forename: Ju-Liang
authors.initials: JL
authors.lastname: Hsieh
authors.forename: Chieh-Chen
authors.initials: CC
authors.lastname: Huang
mesh_terms: D000327:Adsorption; D000818:Animals; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008628:Mercury / Q000378:metabolism* / Q000494:pharmacology; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D018272:Porins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017210:Tilapia
chemical_list: D029941:Fish Proteins; D008565:Membrane Proteins; C113724:OmpC protein; D018272:Porins; D011993:Recombinant Fusion Proteins; D008668:Metallothionein; D008628:Mercury