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Journal of Bacteriology, September 2008, p. 6228-6233, Vol. 190, No. 18
0021-9193/08/$08.00+0     doi:10.1128/JB.00595-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

TolC-Dependent Exclusion of Porphyrins in Escherichia coli{triangledown}

Ryoko Tatsumi and Masaaki Wachi*

Department of Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan

Received 30 April 2008/ Accepted 7 July 2008

We found that Escherichia coli tolC mutants showed increased sensitivity to 5-aminolevulinic acid (ALA), a precursor of porphyrins. The tolC mutant cells grown in the presence of ALA showed a reddish brown color under visible light and a strong red fluorescence under near-UV irradiation. Fluorescence spectrometry and high-performance liquid chromatography analysis showed that the tolC mutant cells grown in the presence of ALA accumulated a large amount of coproporphyrin(ogen) intracellularly. In contrast, the wild-type cells produced coproporphyrin extracellularly. The tolC mutant cells grown in the presence of ALA, which were capable of surviving in the dark, were killed by near-UV irradiation, suggesting that the intracellular coproporphyrin(ogen) renders these cells photosensitive. These results suggest that the TolC-dependent efflux system is involved in the exclusion of porphyrin(ogen)s in E. coli.

* Corresponding author. Mailing address: Department of Bioengineering, Tokyo Institute of Technology, 4259-J2-14 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan. Phone: 81-45-924-5770. Fax: 81-45-924-5820. E-mail: mwachi{at}bio.titech.ac.jp

{triangledown} Published ahead of print on 18 July 2008.

Journal of Bacteriology, September 2008, p. 6228-6233, Vol. 190, No. 18
0021-9193/08/$08.00+0     doi:10.1128/JB.00595-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



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