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Antimicrobial Agents and Chemotherapy, March 2000, p. 522-527, Vol. 44, No. 3
Centre for Photobiology and Photodynamic
Therapy,1 School of Biochemistry and
Molecular Biology,2 and Department of
Colour Chemistry,3 University of Leeds, Leeds
LS2 9JT, United Kingdom
Received 21 July 1999/Returned for modification 14 October
1999/Accepted 29 November 1999
Previous studies have shown that a cationic water-soluble
pyridinium zinc phthalocyanine (PPC) is a powerful photosensitizer that
is able to inactivate Escherichia coli. In the current work incubation of E. coli cells with PPC in the dark caused
alterations in the outer membrane permeability barrier of the cells,
rendering the bacteria much more sensitive to hydrophobic compounds,
with little effect seen with hydrophilic compounds. Addition of
Mg2+ to the medium prior to incubation of the cells with
PPC prevented these alterations in the outer membrane permeability
barrier. The presence of Mg2+ in the medium also prevented
the photoinactivation of E. coli cells with PPC. These
results are consistent with the hypothesis that PPC gains access across
the outer membrane of E. coli cells via the self-promoted
uptake pathway, a mechanism of uptake postulated for the uptake of
other cationic compounds across the outer membranes of gram-negative bacteria.
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Mechanism of Uptake of a Cationic Water-Soluble
Pyridinium Zinc Phthalocyanine across the Outer Membrane of
Escherichia coli
*
Corresponding author. Mailing address: School of
Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT,
United Kingdom. Phone: 0113 2333166. Fax: 0113 2333017. E-mail:
S.B.Brown{at}leeds.ac.uk.
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