The photocatalytic inactivation of pathogenic bacteria in water was investigated systematically with AgBr/TiO2 under visible light (lambda > 420 nm) irradiation. The catalyst was found to be highly effective for the killing of Escherichia coli, a Gram-negative bacterium, and Staphylococcus aureus, a Gram-positive bacterium. The decomposition of the cell wall and cell membrane was directly observed by TEM and further confirmed by K+ leakage from the inactivated bacteria. A possible cell damage mechanism by visible light-driven AgBr/TiO2 is proposed. In addition, the effects of pH, inorganic ions on bacterial photocatalytic inactivation were investigated. The electrostatic force interaction of the bacteria-catalyst is crucial for the efficiency of disinfection. Moreover, AgBr/TiO2 Supported on porous nickel showed much higher bactericidal activity than fixed P25 TiO2 under visible or near UV light irradiation. (c) 2007 Elsevier B.V. All rights reserved.