The investigations on the kinetics of photocatalytic inactivation of bacteriophages, lactic bacteria and lysogenic lactic bacteria have shown that the rate of bacterial inactivation is ca. 10 times less than the inactivation of bacteriophages. Titania-assisted photorelease of bacteriophages from lysogenic bacteria proves that photogenerated reactive oxygen species affect the deoxyribonucleic acid (DNA) of bacteria before their deactivation. On this basis a novel photocatalytic method of a prophage induction to the lytic cycle and detection of lysogenic bacteria is proposed.