Quantifying the membrane potential during E. coli growth stages

The presence of the resting membrane potential has a strong effect on the dielectric behavior of cell suspensions. Using this observation and a well-established theoretical model, the low frequency dielectric dispersion curves of E coli cell suspensions are de-convoluted to obtain the resting membrane potential of E coli cells at various growth stages. Four regions of the exponential growth stage are investigated and the measurements indicate that the membrane depolarizes from -220 mV in the early exponential phase to -140 mV in the late exponential phase. The conductivity of the cell suspension is also found to decrease as the cells progress from the early to the late exponential phases. (C) 2009 Elsevier B.V. All rights reserved.