The roles of bacterial cellular components, namely, fatty acid profile and coenzyme A, in photocatalytic inactivation of bacteria were investigated. Escherichia coli BW25113, as a "parental strain", and its isogenic single-gene deletion mutants E. coli JW1081 (fabF(-) mutant) and E. coli JW3942 (coaA(-) mutant) showed different susceptibilities towards photocatalytic inactivation by titanium dioxide (TiO(2), irradiated by UVA lamps (? = 365 nm)). Regulating the fatty acid composition through pre-incubation temperature adjustment demonstrated the crucial role of cell membrane fatty acid profile in bacterial susceptibility towards photocatalytic inactivation, while the lower coenzyme A level in coaA(-) mutant correlated well with its lower susceptibility towards photocatalytic inactivation. Furthermore, transmission electron microscopic study demonstrated the photocatalytic destruction process of bacterial cells. This is the first study using single-gene deletion mutants to explore better understanding of the photocatalytic inactivation mechanism of E. coli.