Blue Light Phototoxic Effect on Fusobacterium nucletum Membrane and DNA

Objectives: Previously we have shown the phototoxic effect of blue light against anaerobic VSC producing oral bacteria. The aim of the present investigation was to study the phototoxic antibacterial mechanism.
Methods: Fusobacterium nucleatum PK1594 was exposed to high intensity blue light (Plasma arc 400-500nm) in different exposure times (0, 70, 140 and 280sec). Following exposure the effect on cell membrane permeability was studied using fluorescence microscopy, intra cellular proteins were evaluated using SDS-PAGE densitometry and DNA fragmentation was defined colorimetrically following ultrafiltration.
Results: Results of the present study showed that the exposure of Fusobacterium nucletum to high intensity blue light resulted in significantly increased cell membrane damage concomitant with the increase in exposure time. This was demonstrated by the increased membrane permeability to ethidium as well as the reduction in intra cellular proteins content. DNA fragmentation which also increased with exposure time showed slight reduction at 280 sec.
Conclusions: Taken together these results suggest that the main phototoxic effect of blue light against Fusobacterium nucletum is cell membrane damage followed by DNA fragmentation.