The photocatalytic disinfection of Escherichia coli (E. coil) and Staphylococcus aureus (S. aureus) was investigated systematically with polythiophene/MnO2 (PTh/MnO2) nanocomposite photocatalyst under solar light irradiation. The prepared PTh/MnO2 nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrum (FT-IR) and ultraviolet and visible absorption spectrum (UV-vis). The influence parameters of disinfection by PTh/MnO2 nanocomposite, such as irradiation time and concentration of photocatalyst were studied. Further investigation indicated that almost all (99.9%) of the initial bacteria were killed after 6 h incubation at 37 degrees C in the presence of 1 mg/mL PTh/MnO2 photocatalyst under solar light irradiation. During the photocatalytic process, the hydroxyl radical (center dot OH) was generated under irradiation, which played a key role in the inactivation of bacteria. The morphological change of the bacteria during the bactericidal process could be observed from TEM images. This work provides a potential effective nanocomposite photocatalyst to disinfect E. coli and S. aureus under solar light irradiation. (C) 2011 Elsevier B.V. All rights reserved.