title: Mechanism of uptake of a cationic water-soluble pyridinium zinc phthalocyanine across the outer membrane of Escherichia coli.
abstract: 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 Mg(2+) to the medium prior to incubation of the cells with PPC prevented these alterations in the outer membrane permeability barrier. The presence of Mg(2+) 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.
authors.affiliation: Centre for Photobiology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Minnock
authors.forename: D I
authors.initials: DI
authors.lastname: Vernon
authors.forename: J
authors.initials: J
authors.lastname: Schofield
authors.forename: J
authors.initials: J
authors.lastname: Griffiths
authors.forename: J H
authors.initials: JH
authors.lastname: Parish
authors.forename: S B
authors.initials: SB
authors.lastname: Brown
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002250:Carbon Radioisotopes / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002463:Cell Membrane Permeability; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism*; D054833:Isoindoles; D008274:Magnesium / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009942:Organometallic Compounds / Q000378:metabolism*; D017319:Photosensitizing Agents / Q000378:metabolism; D011524:Protoporphyrins / Q000378:metabolism; D017967:Zinc Compounds
chemical_list: D000900:Anti-Bacterial Agents; D002250:Carbon Radioisotopes; D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D017967:Zinc Compounds; C052159:Zn(II)-phthalocyanine; C028025:protoporphyrin IX; D008274:Magnesium