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Applied and Environmental Microbiology, January 2004, p. 43-51, Vol. 70, No. 1
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.1.43-51.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Measurement of Biologically Available Naphthalene in Gas and Aqueous Phases by Use of a Pseudomonas putida Biosensor

Christoph Werlen, Marco C. M. Jaspers, and Jan Roelof van der Meer^*

Process of Environmental Microbiology and Molecular Ecotoxicology, Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH 8600 Dübendorf, Switzerland

Received 14 July 2003/ Accepted 8 October 2003

Genetically constructed microbial biosensors for measuring organic pollutants are mostly applied in aqueous samples. Unfortunately, the detection limit of most biosensors is insufficient to detect pollutants at low but environmentally relevant concentrations. However, organic pollutants with low levels of water solubility often have significant gas-water partitioning coefficients, which in principle makes it possible to measure such compounds in the gas rather than the aqueous phase. Here we describe the first use of a microbial biosensor for measuring organic pollutants directly in the gas phase. For this purpose, we reconstructed a bioluminescent Pseudomonas putida naphthalene biosensor strain to carry the NAH7 plasmid and a chromosomally inserted gene fusion between the sal promoter and the luxAB genes. Specific calibration studies were performed with suspended and filter-immobilized biosensor cells, in aqueous solution and in the gas phase. Gas phase measurements with filter-immobilized biosensor cells in closed flasks, with a naphthalene-contaminated aqueous phase, showed that the biosensor cells can measure naphthalene effectively. The biosensor cells on the filter responded with increasing light output proportional to the naphthalene concentration added to the water phase, even though only a small proportion of the naphthalene was present in the gas phase. In fact, the biosensor cells could concentrate a larger proportion of naphthalene through the gas phase than in the aqueous suspension, probably due to faster transport of naphthalene to the cells in the gas phase. This led to a 10-fold lower detectable aqueous naphthalene concentration (50 nM instead of 0.5 µM). Thus, the use of bacterial biosensors for measuring organic pollutants in the gas phase is a valid method for increasing the sensitivity of these valuable biological devices.

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* Corresponding author. Present address: Department of Fundamental Microbiology, University of Lausanne, BÂtiment de Biologie, CH-1015 Lausanne, Switzerland. Phone: 41-21 692 5630. Fax: 41-21 692 5635. E-mail: JanRoelof.vanderMeer{at}imf.unil.ch.

Present address: Department of Applied Microbiology and Gene Technology, TNO Nutrition and Food Research, 3700 AJ Zeist, The Netherlands.

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Applied and Environmental Microbiology, January 2004, p. 43-51, Vol. 70, No. 1
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.1.43-51.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.