• Open Access

Whole-cell biosensors for detection of heavy metal ions in environmental samples based on metallothionein promoters from Tetrahymena thermophila

Authors

  • Francisco Amaro,

    1. Departamento de Microbiología-III, Facultad de Biología, C/. José Antonio Novais, 2, Universidad Complutense (UCM), 28040 Madrid, Spain.
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  • Aaron P. Turkewitz,

    1. Department of Molecular Genetics and Cell Biology, University of Chicago, Cummings Life Science Center, 920 East 58th Street, Chicago, IL. 60637, USA
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  • Ana Martín-González,

    1. Departamento de Microbiología-III, Facultad de Biología, C/. José Antonio Novais, 2, Universidad Complutense (UCM), 28040 Madrid, Spain.
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  • Juan-Carlos Gutiérrez

    Corresponding author
    1. Departamento de Microbiología-III, Facultad de Biología, C/. José Antonio Novais, 2, Universidad Complutense (UCM), 28040 Madrid, Spain.
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E-mail juancar@bio.ucm.es; Tel. (+34) 9 1394 4968; Fax (+34) 9 1394 4964.

Summary

Heavy metals are among the most serious pollutants, and thus there is a need to develop sensitive and rapid biomonitoring methods for heavy metals in the environment. Critical parameters such as bioavailability, toxicity and genotoxicity cannot be tested using chemical analysis, but only can be assayed using living cells. A whole-cell biosensor uses the whole cell as a single reporter incorporating both bioreceptor and transducer elements. In the present paper, we report results with two gene constructs using the Tetrahymena thermophila MTT1 and MTT5 metallothionein promoters linked with the eukaryotic luciferase gene as a reporter. This is the first report of a ciliated protozoan used as a heavy metal whole-cell biosensor. T. thermophila transformed strains were created as heavy metal whole-cell biosensors, and turn on bioassays were designed to detect, in about 2 h, the bioavailable heavy metals in polluted soil or aquatic samples. Validation of these whole-cell biosensors was carried out using both artificial and natural samples, including methods for detecting false positives and negatives. Comparison with other published cell biosensors indicates that the Tetrahymena metallothionein promoter-based biosensors appear to be the most sensitive eukaryotic metal biosensors and compare favourably with some prokaryotic biosensors as well.

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