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 10 3 and 10 7. In addition, the EIS investigation suggests further decrease in the detected cells concentration to be possible.