Photosensitized Inactivation of E. Coli Cells in Toluidine Blue‐light System

E. coli cells were inactivated with visible light in the presence of toluidine blue as a photo‐sensitizer. This photodynamic effect was partially protected with α‐tocopherol. Not only pH but the concentration of the buffer during irradiation also affected the survival. The addition of osmotic stabilizers such as KCI, glycerol and polyethyleneglycol to the buffer increased the survival. The difference in singlet oxygen production in these reaction mixtures could not be related to these features. Furthermore, the survival was also dependent upon both irradiation temperature and cultivation temperature of the cells. These results with E. coli cells support the notion that one of the primary targets of toluidine blue sensitized photodynamic inactivation is cytoplasmic membrane, although other factors than cytoplasmic membrane also influence the survival of the cells.