Collins Y E, Stotzky G
Laboratory of Microbial Ecology, Department of Biology, New York University 10003.
Appl Environ Microbiol. 1992 May;58(5):1592-600. doi: 10.1128/aem.58.5.1592-1600.1992.
The electrokinetic patterns of four bacterial species (Bacillus subtilis, Bacillus 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 kaolinite were net negatively charged at pH values above their isoelectric points (pI) in the presence of Na, Mg, Hg, and Pb at an ionic strength (mu) of 3 x 10(-4); montmorillonite has no pI and was net negatively charged at all pH values in the presence of these metals. However, the charge of some bacteria, S. cerevisiae, and kaolinite changed to a net positive charge (charge reversal) in the presence of Cd, Cr, Cu, Ni, and Zn at pH values above 5.0 (the pH at which charge reversal occurred differed with the metal) and then, at higher pH values, again became negative. The charge of the bacteria and S. cerevisiae also reversed in solutions of Cu and Ni with a mu of greater than 3 x 10(-4), whereas there was no reversal in solutions with a mu of less than 3 x 10(-4). The clays became net positively charged when the mu of Cu was greater than 3 x 10(-4) and that of Ni was greater than 1.5 x 10(-4). The charge of the cells and clays also reversed in solutions containing both Mg and Ni or both Cu and Ni (except montmorillonite) but not in solutions containing both Mg and Cu (except kaolinite) (mu = 3 x 10(-4)). The pIs of the cells in the presence of the heavy metals were at either higher or lower pH values than in the presence of Na and Mg. Exposure of the cells to the various metals at pH values from 2 to 9 for the short times (ca. 10 min) required to measure the electrophoretic mobility did not affect their viability. The specific adsorption on the cells and clays of the hydrolyzed species of some of the heavy metals that formed at higher pH values was probably responsible for the charge reversal. These results suggest that the toxicity of some heavy metals to microorganisms varies with pH because the hydrolyzed speciation forms of these metals, which occur at higher pH values, bind on the cell surface and alter the net charge of the cell.(ABSTRACT TRUNCATED AT 400 WORDS)
通过微电泳测定了四种细菌（枯草芽孢杆菌、巨大芽孢杆菌、铜绿假单胞菌和放射土壤杆菌）、两种酵母（酿酒酵母和白色念珠菌）以及两种粘土矿物（蒙脱石和高岭土）在重金属（镉、铬、铜、汞、镍、铅和锌）的氯化物盐以及钠和镁存在下的电动模式。在离子强度（μ）为3×10⁻⁴的情况下，在钠、镁、汞和铅存在时，细胞和高岭土在高于其等电点（pI）的pH值下带净负电荷；蒙脱石没有等电点，在这些金属存在时在所有pH值下都带净负电荷。然而，在pH值高于5.0（电荷反转发生的pH值因金属而异）时，在镉、铬、铜、镍和锌存在下，一些细菌、酿酒酵母和高岭土的电荷变为净正电荷（电荷反转），然后在更高的pH值下又变为负电荷。在μ大于3×10⁻⁴的铜和镍溶液中，细菌和酿酒酵母的电荷也会反转，而在μ小于3×10⁻⁴的溶液中则不会反转。当铜的μ大于3×10⁻⁴且镍的μ大于1.5×10⁻⁴时，粘土带净正电荷。在含有镁和镍或铜和镍的溶液中（蒙脱石除外），细胞和粘土的电荷也会反转，但在含有镁和铜的溶液中（高岭土除外）（μ = 3×10⁻⁴）则不会。在重金属存在下细胞的等电点比在钠和镁存在时的pH值更高或更低。在测量电泳迁移率所需的短时间（约10分钟）内，将细胞暴露于pH值为2至9的各种金属中不会影响其活力。在较高pH值下形成的一些重金属水解物种在细胞和粘土上发生的特异性吸附可能是电荷反转的原因。这些结果表明，一些重金属对微生物的毒性随pH值而变化，因为这些金属在较高pH值下形成的水解物种形态会结合在细胞表面并改变细胞的净电荷。（摘要截短至400字）
