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 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.

Effects of pH and ionic strength on the adsorption of Cs, Sr, Eu, Zn, Cd and Hg byPseudomonas putida

“…In addition to the bacteria themselves, the exudate was, although to a lesser extent, capable of proton binding. The surface carried a negative net charge over the entire pH interval studied accordin G to the electrophoretic light scattering (Figure 5), which is in agreement with previous investigations of other bacteria and yeasts (Harden andHarris, 1953, Collins andStotzky, 1992). A negatively charged surface would electrostatically attract ions of opposite charge in a non-specific way.…”

The Effect of Ionic Strength on the Adsorption of H+, Cd2+, Pb2+, and Cu2+byBacillus subtilisandBacillus licheniformis:A Surface Complexation Model

“…[9] metal ratios. Further evidence in support of the 1:1 stoichiometry for the metal-bacteria surface complexes is provided by the electrophoretic mobility experiments of Collins and The mass action equations corresponding to the above equilibria are Stotzky (29), who report that bacterial cells, which are nega- tively charged in the absence of metals, become positively (K observed ). We account for the electrostatic interactions with the relationship charged when divalent metals are present.…”

Biosorption of heavy metals from industrial waste water by Geobacillus thermodenitrificans

“…Solution pH influences cell surface metal binding sites and the interaction of these ions with bacteria may be primarily electrostatic in nature. pH affects the network of negative charges on the surface of the biosorbing cells (especially in case of Gram-positive bacteria) and the chemistry of the walls, as well as physicochemistry and hydrolysis of the metal [40,45].…”