Changes in the surface charge of bacteria caused by heavy metals do not affect survival

Abstract

Bacillus subtilis and Agrobacterium radiobacter remained viable when exposed to Ni (1 × 10−4 M; ionic strength (μ) = 3 × 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 × 10−4 M; μ = 3 × 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 μ 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.Key words: heavy metals, electrokinetic properties, survival of bacteria.