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 muS cm(-1)), almost double that of active cells (560+/-20 muS cm(-1)), while that of dead (autoclaved) M. smegmatis cells was the highest (950+/-15 muS cm(-1)) overall. It was also found that at 80 kHz, 900 muS 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 muS 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.