The electrokinetic patterns of four bacterial species (Bacillus subtilis, BaciUlus megaterium, Pseudomonas aeruginosa, and Agrobacterium radiobacter), two yeasts (Saccharomyces cerevisiae and Candida albicans), and two clay minerals (montmorillonite and kaolinite) in the presence of the chloride salts of the heavy metals, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, and of Na and Mg were determined by microelectrophoresis. The cells and

Bacillus subtilis and Agrobacterium radiobacter remained viable when exposed to Ni (1 x 10(-4)M; ionic strength (mu) = 3 x 10(-4)) at pH values known to cause a change of the net negative charge of the cells to a net positive charge (charge reversal). The gross morphology, as determined by scanning electron microscopy, of these and other bacteria and of Saccharomyces cerevisiae was not altered in the presence of Ni, Cu, and Zn (1 x 10(-4) M; mu = 3 x 10(-4)), which caused a charge reversal at pH values between 6.0 and 9.0. Similar results were obtained in the presence of Na and Mg, which did not cause charge reversal at the same mu and pH values. These results confirmed that cells remain viable when their surface charge is changed in the presence of some heavy metals at high pH values.