An electrochemical disinfection system employing a honeycombed platinum coated titanium electrode was developed for the disinfection of seawater. Cell suspensions (2 1, 103 cells/ml) of the fish pathogens, Vibrio alginolyticus, Edwardsiella tarda, Lactococcus garvieae and Vibrio anguillarum were circulated in a reactor equipped with 10 sets of these electrodes at a flow rate of 200 ml/min with an applied potential of 1.0 V vs. Ag/AgCl reference electrode. The circulated cells were completely disinfected after 3 h of treatment, whereas free residual chlorine generated due to seawater electrolysis was below 0.1 ppm. In addition, a diphenyl-1-pyrenylphosphine fluorescent assay revealed that lipid peroxidation in the cell membranes of disinfected bacteria was induced probably by reactive oxygen species generated during electrochemical treatment. (C) 2013, The Society for Biotechnology, Japan. All rights reserved.