Low-intensity red
lasers are proposed for treatment of oral
aphthous ulcers based on biostimulative effects. However, effects of low-intensity
lasers at fluences used in clinical protocols on
DNA are controversial. The aim of this work was to evaluate the effects of low-intensity red
laser on survival and induction of filamentation of Escherichia coli cells, and induction of DNA lesions in bacterial plasmids. Escherichia coli cultures were exposed to
laser (660 nm, 100 mW, 25 and 45 J cm(-2)) to study bacterial survival and filamentation. Also, bacterial plasmids were exposed to
laser to study DNA lesions by electrophoretic profile and action of
DNA repair enzymes. Data indicate that low-intensity red
laser: (i) had no effect on survival of E. coli wild type,
exonuclease III and
formamidopyrimidine DNA glycosylase/MutM
protein but decreased the survival of
endonuclease III deficient cultures; (ii) induced bacterial filamentation, (iii) there was no alteration in the electrophoretic profile of plasmids in
agarose gels, (iv) there was no alteration in the electrophoretic profile of plasmids incubated with
formamidopyrimidine DNA glycosylase/MutM
protein and
endonuclease III
enzymes, but it altered the electrophoretic profile of plasmids incubated with
exonuclease III. Low-intensity red
laser at therapeutic fluences has an effect on the survival of E. coli
endonuclease III deficient cells, induces bacterial filamentation in E. coli cultures and DNA lesions targeted by
exonuclease III.