The electrokinetic surface of five enteropathogenic Escherichia coli serogroups

The surface ionogenicity of five enteropathogenic Escherichia coli serogroups (O111:H2, O111:H12, O125:H9, O119:H6, and O26:H11) was investigated by electrokinetical approaches. All of the studied surfaces are negatively charged with their mean values of zeta potential (ZP) varying from -9.0 (O26:H11) to -11.9 mV (O111:H2). The populational behavior of the all bacteria are similar since very high ZP values varying from -26 to -30 mV were obtained in experiments carried out with the slip plane calculated at 6.83 nm from the cell surface. All the surfaces are extremely acidic, because the isoelectrophoretic points are localized at pH values below 3.0. Treatment of the microorganisms with neuraminidase did not alter their surface anionogenicity, while treatment with trypsin or phospholipase C reduced their negative charge.