title: Improving the sensitivity of bacterial bioreporters for heavy metals.
abstract: Whole-cell bacterial bioreporters represent a convenient testing method for quantifying the bioavailability of contaminants in environmental samples. Despite the fact that several bioreporters have been constructed for measuring heavy metals, their application to environmental samples has remained minimal. The major drawbacks of the available bioreporters include a lack of sensitivity and specificity. Here, we report an improvement in the limit of detection of bacterial bioreporters by interfering with the natural metal homeostasis system of the host bacterium. The limit of detection of a Pseudomonas putida KT2440-based Zn/Cd/Pb-biosensor was improved by a factor of up to 45 by disrupting four main efflux transporters for Zn/Cd/Pb and thereby causing the metals to accumulate in the cell. The specificity of the bioreporter could be modified by changing the sensor element. A Zn-specific bioreporter was achieved by using the promoter of the cadA1 gene from P. putida as a sensor element. The constructed transporter-deficient P. putida reporter strain detected Zn(2+) concentrations about 50 times lower than that possible with other available Zn-bioreporters. The achieved detection limits were significantly below the permitted limit values for Zn and Pb in water and in soil, allowing for reliable detection of heavy metals in the environment.
authors.affiliation: Department of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland. anu.leedjarv@helsinki.fi
authors.forename: Anu
authors.initials: A
authors.lastname: Hynninen
authors.forename: Karmen
authors.initials: K
authors.lastname: Tönismann
authors.forename: Marko
authors.initials: M
authors.lastname: Virta
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D004785:Environmental Pollutants / Q000032:analysis* / Q000378:metabolism; D005818:Genetic Engineering; D016623:Ion Pumps / Q000235:genetics / Q000378:metabolism; D017136:Ion Transport; D057230:Limit of Detection; D019216:Metals, Heavy / Q000032:analysis* / Q000378:metabolism; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004785:Environmental Pollutants; D016623:Ion Pumps; D019216:Metals, Heavy