title: Exposure of Porphyromonas gingivalis to red light in the presence of the light-activated antimicrobial agent toluidine blue decreases membrane fluidity.
abstract: Porphyromonas gingivalis, one of the etiological agents of periodontitis, can be killed by red light in the presence of toluidine blue. The purpose of this study was to determine whether this light-induced killing was accompanied by changes in the fluidity of the organism's cytoplasmic membrane. A suspension of the organism was exposed to red light in the presence of toluidine blue, and the membrane fluidity was monitored spectrofluorimetrically by using the membrane probe trimethylammonium diphenyl hexatriene. The fluidity of the organism's cytoplasmic membrane was found to decrease significantly during lethal photosensitization, and this was accompanied by membrane condensation and vacuolation of the cells. Although changes in membrane fluidity are often attributable to lipid peroxidation, malonaldehyde (a product of lipid peroxidation) was not detectable. The disruption of membrane functions associated with a decreased membrane fluidity may contribute to the bactericidal effect of light-activated toluidine blue.
authors.affiliation: Department of Microbiology, Eastman Dental Institute for Oral Health Care Sciences, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
authors.forename: Manpreet
authors.initials: M
authors.lastname: Bhatti
authors.forename: Alexander
authors.initials: A
authors.lastname: MacRobert
authors.forename: Brian
authors.initials: B
authors.lastname: Henderson
authors.forename: Michael
authors.initials: M
authors.lastname: Wilson
mesh_terms: D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D008560:Membrane Fluidity / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D008826:Microbial Sensitivity Tests; D017348:Microscopy, Electron, Scanning Transmission; D017319:Photosensitizing Agents / Q000494:pharmacology*; D016966:Porphyromonas gingivalis / Q000187:drug effects* / Q000528:radiation effects / Q000648:ultrastructure; D014048:Tolonium Chloride / Q000494:pharmacology*
chemical_list: D017319:Photosensitizing Agents; D014048:Tolonium Chloride