title: Influence of blue light on Streptococcus mutans re-organization in biofilm.
abstract: Our aim was to examine the viability and structure of new biofilm formed by Streptococcus mutans that was previously exposed to blue light. S. mutans bacteria were grown to form a mature biofilm, that was exposed to blue light (wavelengths, 400-500 nm) for 1-10 min (equivalent to 68-680 J/cm(2)). Biofilm was dispersed by sonication, and then the suspended bacteria were grown to re-organize as a new biofilm. Biofilm formation after 2, 4, and 6 h, was examined by viable counts and by confocal laser scanning microscopy using live/dead bacterial staining. A significant decrease in bacterial viability was found in the 6h biofilms formed by bacteria that had been previously exposed to blue light for 7 or 10 min. Confocal microscopy images showed a decrease in the live/dead bacterial ratio after 3-10 min of light exposures. Dead bacteria were mainly at the outer layers of the biofilm. Exposure of S. mutans in biofilm to blue light affected the re-formation of a new biofilm, showing an increase in the amount of dead bacteria. This phenomenon suggests that blue light has a delayed antibacterial effect, although it does not interfere with bacterial capability to reform an initial biofilm.
authors.affiliation: Department of Prosthodontics, The Hebrew University-Hadassah School of Dental Medicine, Jerusalem 91120, Israel.
authors.forename: Daniella
authors.initials: D
authors.lastname: Chebath-Taub
authors.forename: Doron
authors.initials: D
authors.lastname: Steinberg
authors.forename: John D B
authors.initials: JD
authors.lastname: Featherstone
authors.forename: Osnat
authors.initials: O
authors.lastname: Feuerstein
mesh_terms: D018441:Biofilms / Q000254:growth & development* / Q000528:radiation effects*; D018914:Cells, Immobilized / Q000528:radiation effects; D003116:Color; D008027:Light; D050296:Microbial Viability / Q000528:radiation effects; D013295:Streptococcus mutans / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D013997:Time Factors