Separation by dielectrophoresis of dormant and nondormant bacterial cells of Mycobacterium smegmatis

The dielectrophoretic behavior of active, dead, and dormant Mycobacterium smegmatis bacterial cells was studied. It was found that the 72-h-old dormant cells had a much higher effective particle conductivity (812 +/- 10 mu S cm(-1)), almost double that of active cells (560 +/- 20 mu S cm(-1)), while that of dead (autoclaved) M. smegmatis cells was the highest (950 +/- 15 mu S cm(-1)) overall. It was also found that at 80 kHz, 900 mu S cm(-1) dead cells were attracted at the edges of interdigitated castellated electrodes by positive dielectrophoresis, but dormant cells were not. Similarly, at 120 kHz, 2 mu S cm(-1) active cells were attracted and dormant cells were not. Using these findings a dielectrophoresis-based microfluidic separation system was developed in which dead and active cells were collected from a given cell suspension, while dormant cells were eluted. (C) 2010 American Institute of Physics. [doi:10.1063/1.3435335]