EFFECT OF BIOCIDE CONCENTRATION ON ELECTROROTATION SPECTRA OF YEAST-CELLS

The effect of the biocide Cosmocil (polyhexanide) at different concent rations on the electrorotation spectra of yeast cells is investigated over the frequency range from 1 kHz to 10 MHz. The dielectric properti es of the yeast, before and after biocide treatment, were deduced from the electrorotation spectra using two-shell ellipsoid modelling metho ds that have been well tested for other heterogeneous biological syste ms. The results show a gradual increase in the cytoplasmic membrane co nductivity with increasing biocide concentration, rather than an 'all- or-nothing' breakdown of the membrane. The technique gives a quantitat ive analysis of the toxic damage by chemicals to cells and can be expl oited in the development of new pharmacological agents.