COMPARISON BETWEEN THE BEHAVIOR OF YEAST AND BACTERIA IN A NONUNIFORM ALTERNATING ELECTRIC-FIELD

Dielectrophoretic measurements in a new chamber with a configuration of electrodes supplying a high spherical symmetry electric field were carried out. Saccharomyces cerevisiae, Kloeckera apiculata and Citrobacter freundii at a frequency range from 50 KHz to 7 MHz and both viable and non-viable states were experimented on. The results obtained for viable cells confirm that the yield spectrum is very similar for all three microorganisms, despite their essential differences. In dead cells, cut-off frequencies as the boundary between both positive and negative dielectrophoretic behaviour were found for the yeasts S. cerevisiae and K. apiculata. In contrast, in the case of the dead bacteria of C. freundii, this cut-off point was not found within the frequency range studied. The Maxwell-Wagner and double ionic layer appear to be the principal mechanisms responsible for the dielectrophoretic results obtained, concealing those produced by the large differences in morphology and structure in these microorganisms. © 1990.