Electrical impedance spectroscopy with bacterial biofilms: neuronal-like behaviour

Abstract

Negative capacitance at low frequencies for neurons was first demonstrated in 1941 (Kenneth S. Cole) using extracellular electrodes. The phenomenon subsequently was explained by Cole using the Hodgkin-Huxley model and is due to the activity of voltage-gated potassium ion channels. We show that E. coli biofilms exhibit significant stable negative capacitances at low frequencies when they experience a small DC bias voltage in electrical impedance spectroscopy experiments. Using a frequency domain Hodgkin-Huxley model, we characterize the conditions for the emergence of this feature and demonstrate that the negative capacitance exists only in biofilms containing living cells. Furthermore, we established the importance of the voltage-gated potassium ion channel, Kch, using knock-down mutants. The experiments provide further evidence for voltage-gated ion channels in E. coli and a new, low-cost method to probe biofilm electrophysiology e.g. to understand the efficacy of antibiotics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=67 SRC="FIGDIR/small/568527v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@e3df05org.highwire.dtl.DTLVardef@46c5d2org.highwire.dtl.DTLVardef@6572a6org.highwire.dtl.DTLVardef@4a104a_HPS_FORMAT_FIGEXP M_FIG C_FIG