Electrode and Electrolyte Impedance in the Detection of Bacterial Growth

The growth of bacteria in culture was found to produce impedance changes between two metal electrodes which result from changes both in conductivity and electrode impedance. Predominant changes were found in the imaginary impedance component at low frequency. Linear ac impedance characteristics were found in the relation between real and imaginary impedance components before and during bacterial growth. This linear relation is consistent with characteristics of diffusion and electron exchange (oxidation-reduction) at the electrode. The measurement of impedance in this system was limited below 100 Hz by nonlinearity in the voltage-current relation. Bacterial growth was best detected with stainless steel electrodes at low frequency (100 Hz) and including the imaginary component of impedance.