Mercury resistance and accumulation in Escherichia coli with cell surface expression of fish metallothionein |
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Authors: | Kuo-Hsing Lin Mei-Fang Chien Ju-Liang Hsieh Chieh-Chen Huang |
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Institution: | (1) Department of Life Sciences, National Chung Hsing University, Taichung, 402, Taiwan;(2) Center for Marine Environmental Studies, Ehime University, 3, Bunkyo-cho, Matsuyama 790-8577, Japan;(3) Division of Molecular and Genomic Medicine, National Health Research Institute, Miaoli, 350, Taiwan; |
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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. |
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