A low cost, reagent free, Escherichia coli sensor is demonstrated with graphene, on transparent flexible acetate substrate. Graphene is grown on 100 μm thick Cu foil, using CVD process and subsequently transferred on to a flexible acetate substrate. Gold electrodes are deposited on graphene to form a two terminal, interdigitated capacitor structure. Impedance spectroscopy (10 Hz to 100 kHz) is performed to characterize the change in impedance, as a function of E. coli concentration on graphene surface. The residual methyl groups on graphene, resulting from the transfer process, act as binding sites for E. coli. It has been observed that the resistance of graphene decreases with increasing E. coli concentration. This is due to the increased hole doping induced by negatively charged E. coli. A sensitivity of 60% is achieved for an E. coli concentration of 4.5 × 107 cfu/ml. An equivalent RC model is proposed to explain the sensing mechanism. © 2013 Elsevier B.V.