The selective control of pathogenic bacteria is an ongoing challenge. A strategy is proposed that combines targeted binding of the bacterium, using antibodies, with their photoactivated oxidative destruction. Photoactive colloidal TiO2 was first derivatized with E. coli antibodies (EA-TiO2). When mixtures of the organisms E. coli and Pseudomonas putida ( P. putida ) were exposed to modified EA-TiO2, the particles preferentially selected E. coli for surface binding. Two consequences arose from surface bioconjugation: bacteria were found to flocculate upon mixing at appropriate ratios of EA-TiO2/ E. coli , and EA-TiO2-bound E. coli underwent cell death after exposure to UV light. In the former case, flocculation of the bacteria was optimal at ~50 EA-TiO2 particles per E. coli . Selective flocculation provides an alternative strategy for pathogen removal. With respect to UV disinfection, as few as 26 EA-TiO2 particles per E. coli gave a 10 000-fold decrease in viable bacteria. Thus, it is possible to selectively target and kill one type of bacteria in a mixture of pathogens. The results give support to the proposal that photocatalytic TiO2 most effectively delivers an oxidizing agent when the titania is bound to the bacterial surface.