The challenge to achieve efficient disinfection and microbial control without harmful disinfection byproducts calls for developing new technologies. Magnetic-graphene oxide (M-GO) with magnetic iron oxide nanoparticles well dispersed on graphene oxide (GO) nanosheets exerted excellent antibacterial activity against Escherichia coil. The antibacterial performance of M-GO was dependent on the concentration and the component mass ratio of M/GO. The synergetic antibacterial effect of M-GO was observed with M/GO mass ratio of 9.09. TEM images illustrated the interaction between E. coil cells and M-GO nanocomposites. M-GO nanomaterials were possible to deposit on or penetrate into cells leading to leakage of intercellular contents and loss of cell integrity. The inactivation mechanism of E. coil by M-GO was supposed to result from both the membrane stress and oxidation stress during the incubation period. M-GO with excellent antibacterial efficiency against E. coil and separation-convenient property from water could be potent bactericidal nanomaterials for water disinfection. (C) 2014 Published by Elsevier B.V.