For the elucidation of the mechanism underlying the photocatalytic bactericidal activity of titanium dioxide (TiO2), we focused on the peptidoglycan layer, a component of the bacterial cell wall. The effect of this layer on the photocatalytic bactericidal activity of TiO2 was evaluated by determining the survival rates of Lactobacillus plantarum (intact cells) and its protoplast cells. Mesoplasma florum, which does not originally possess the peptidoglycan layer, was also used. Our results revealed that the survival rates of the intact cells were lower than those of the protoplast cells. In addition, there was no significance between the survival rates of M. florum cells and the protoplast cells of L. plantarum. It was suggested that the presence of the peptidoglycan layer increases the bactericidal effect by the photocatalysis.
Keywords: Bactericidal effect; Peptidoglycan; Photocatalysis; Protoplast; TiO2.