In the current work, the synergetic effect of microbial cells and functional nanostructures, such as highly disordered Si nanowires (SiNW-forest), has been exploited to develop a novel whole-cell biosensor. E.Coli microbial cells, expressing and displaying recombinant ZZ proteins, were immobilized onto SiNW-forest electrode. The existence of the microbial cells was verified visually by scanning electron microscopy, and viable counting, and electrochemically using impedance spectroscopy (EIS). The electrochemical impedance spectra show a clear dependence on the number of the microbial cells by allowing the detection of different number of cells in the range between 103 and 107. In addition, the EIS investigation suggests further decrease in the detected cells concentration to be possible.