CHANGES IN THE SURFACE-CHARGE OF BACTERIA CAUSED BY HEAVY-METALS DO NOT AFFECT SURVIVAL

Bacillus subtilis and Agrobacterium radiobacter remained viable when e xposed to Ni (1 x 10(-4) M; ionic strength (mu) = 3 x 10(-4)) at pH va lues known to cause a change of the net negative charge of the cells t o a net positive charge (charge reversal). The gross morphology, as de termined 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 rev ersal 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 t he same mu and pH values. These results confirmed that cells remain vi able when their surface charge is changed in the presence of some heav y metals at high pH values.