Electron Microscopic Studies on Bactericidal Effects of Electrolyzed Acidic Water on Bacteria Derived from Kendo Protective Equipment

ABSTRACT

Objectives: Kendo protective equipment is used without washing for a long time. Staphylococcus saprophyticus, Micrococcus luteus, and Bacillus sphaericus are frequently isolated from the mask (‘men’ in Japanese) of kendo protective equipment during one year. To investigate the bactericidal effects of electrolyzed acidic water on these three bacteria, we observed their cellular structures by electron microscopy after treatment with such water. Methods: Each bacterium isolated from ‘men’ was treated with electrolyzed acidic water and then observed under scanning and transmission electron microscopes. Results: When S. saprophyticus was treated with electrolyzed acidic water and its cellular structures were observed under a transmission electron microscope, ghost cytoplasm was observed, in which no ribosomal granules or fibrous DNA structures were present, and the cell wall inner layer was detached from the outer layer. Under a scanning electron microscope, the structure of the cell wall surface layer was wrinkled, and round pores were partially formed, indicating that the cytoplasmic structures were flushed out of the cells treated with electrolyzed acidic water through the pores formed in the cell wall. In M. luteus, the destruction of ribosomal granules and that of DNA fibers were observed to be similar to those of S. saprophyticus. For B. sphaericus, the effect of electrolyzed acidic water was investigated using vegetative cells. A dissociation between the cytoplasm and cell wall wrinkled the cell surface layer. Conclusion: On the basis of above findings, electrolyzed acidic water was found to destroy the cellular structures of the three bacterial species frequently isolated from kendo men within a short time. Electrolyzed acidic water may be useful for disinfecting of kendo equipment.