Photoelectrocatalytic (PEC) and photocatalytic (PC) inactivation of ancestor Escherichia coil K-12 and its mutant E. coli BW25113 were systematically compared using a TiO2 nanotubular photoanode. The results showed that PEC inactivation was more effective to both bacterial strains than PC process, and E. coli BW25113 showed higher resistance than E. coli K-12 in both PEC and PC systems. The findings indicate that the two strains with different genes are varied in their susceptibilities and responses to the PEC and PC treatments. The h(+) was found to be the major reactive species and predominantly responsible for PEC inactivation. Scanning electron microscopy images demonstrated that the cells were severely damaged and resulted in a leakage of the intracellular components during PEC inactivation process. For a given bacterial strain, no significant effect was found on the PEC inactivation efficiency as different electrolytes were employed. However, in the presence of NaCl or NaBr, PEC inactivation efficiencies of both strains were remarkably enhanced. This phenomenon can be attributed to the efficient formation of halide and dihalide radical anions during PEC process. The different efficiencies of the two bacterial strains under same conditions can be ascribed to their different abilities to resist the inactivation of bacterial strains with different genotypes. (C) 2013 Elsevier B.V. All rights reserved.