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Applied and Environmental Microbiology, November 2008, p. 6730-6738, Vol. 74, No. 21
0099-2240/08/$08.00+0     doi:10.1128/AEM.00498-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Novel Carotenoid-Based Biosensor for Simple Visual Detection of Arsenite: Characterization and Preliminary Evaluation for Environmental Application{triangledown} ,{dagger}

Kazuyuki Yoshida,1 Koichi Inoue,1 Yuko Takahashi,1 Shunsaku Ueda,1 Katsuhiro Isoda,2 Kiyohito Yagi,2 and Isamu Maeda1*

Department of Bioproductive Science, Faculty of Agriculture, Utsunomiya University, 350 Minemachi, Utsunomiya, Tochigi 321-8505, Japan,1 Graduate School of Pharmaceutical Science, Osaka University, 1-6 Yamada-oka, Suita, Osaka 565-0871, Japan2

Received 29 February 2008/ Accepted 28 August 2008

A novel whole-cell arsenite biosensor was developed using the photosynthetic bacterium Rhodopseudomonas palustris no. 7 and characterized. A sensor plasmid containing the operator-promoter region of the ars operon and arsR gene from Escherichia coli and the crtI gene from R. palustris no. 7 was introduced into a blue-green mutant with crtI deleted, R. palustris no. 711. The biosensor changed color in response to arsenite, and the change was obvious to the naked eye after 24 h without further manipulation. Real-time reverse transcription-PCR showed that the crtI mRNA was induced 3-fold at 3 h and 2.5-fold at 6 h after addition of 50 µg/liter arsenite compared with the no-arsenite control, and consistent with this, the relative levels of lycopene and rhodopin also increased compared with the control. Colorimetric analysis of the bacteria showed that the hue angle had clearly shifted from green-yellow toward red in an arsenic dose-dependent manner at 24 h after arsenite addition. This obvious shift occurred irrespective of the culture conditions before arsenite was added, indicating that the color change of the biosensor is stable in water samples containing various concentrations of dissolved oxygen. Finally, assays using samples prepared in various types of mineral water indicated that this biosensor could be used to screen groundwater samples for the presence of arsenite in a variety of locations, even where electricity is not available.

* Corresponding author. Mailing address: Department of Bioproductive Science, Faculty of Agriculture, Utsunomiya University, 350 Minemachi, Utsunomiya, Tochigi 321-8505, Japan. Phone and fax: 81-28-6495477. E-mail: i-maeda{at}cc.utsunomiya-u.ac.jp

{triangledown} Published ahead of print on 5 September 2008.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, November 2008, p. 6730-6738, Vol. 74, No. 21
0099-2240/08/$08.00+0     doi:10.1128/AEM.00498-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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