title: Light-induced modulation of Porphyromonas gingivalis growth.
abstract: The bacterium Porphyromonas gingivalis is a clinically significant agent in periodontitis, a disease for which there is no definitive cure. Several groups have attempted to kill this bacterium using low levels of light in the absence of a photosensitizer, with conflicting results. We hypothesize that it is not possible to kill P. gingivalis by targeting endogenous porphyrins for a photochemical reaction. We demonstrated that irradiation of P. gingivalis with 455 or 625 nm light emitting diodes did not induce a photochemical killing of the cultures. Controlled temperature experiments indicate that irradiation at either wavelength did not significantly impact the growth of P. gingivalis cultures, as compared to non-irradiated controls. Rather, the irradiation caused a temperature increase in the growth medium, which altered the growth of the cultures. These results indicate that heat-induced killing of P. gingivalis could be the mechanism behind successful irradiation experiments with this bacterium.
authors.affiliation: Biomedical Engineering Department, Northwestern University, Evanston, IL 60208, USA. a-izzo@northwestern.edu
authors.forename: Agnella D
authors.initials: AD
authors.lastname: Izzo
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Walsh
mesh_terms: D008027:Light; D010100:Oxygen / Q000494:pharmacology; D016966:Porphyromonas gingivalis / Q000166:cytology / Q000187:drug effects / Q000254:growth & development* / Q000528:radiation effects*; D013696:Temperature
chemical_list: D010100:Oxygen