Impedance Bacteriometry: Medium and interface contributions during bacterial growth

FELICE, CARMELO JOSÉ; VALENTINUZZI, MÁXIMO EUGENIO; VERCELLONE, MARÍA ISABEL; MADRID, ROSSANA ELENA

IEEE Transactions on Biomedical Engineering

Año: 1992 vol. 39 p. 1310 - 1313

We measured impedance in a cell containing culture broth inoculated with E.coli before an during bacterial growth. The electrode interface impedance components (Ri, Xi) and the culture medium componente Rm were separated by making use of the Warburg´s model frequency dependent properties. Measurement were carried out at different frequencies (from 18 Hz to 18 KHz) with a constant current impedance bridge as growth proceeded. It was found that: growth curves for Ri and Xi showed a similar temporal pattern within the frequency range of 18-100 Hz. Dispersion was not observed in Rm, meaning that the same growth resonse was obtained within the 18-18000 Hz range. At low frequency, the resistive and capacitive reactive components, or Rb and Xb, respectively, were diretly measured, where Rb = (2. Ri + Rm) and Xb = 2.Xi, and , at high frequency (above 5 KHz) Rm was obtained (for Zi negligible). Thus, Ri was easily discriminated from Rm by simple arithmetic: Ri = [Rb (lowf) - Rb(high f)]/2. In four experiments, the mximum spread of Xi, Ri and Rm was smaller than 5%, indicating good repeatibility. There is potential new information in dissecting out the growth curve in three separate component curves.