The influence of physical-chemical characteristics of surface modified copper nanoparticles on E. coli cell population growth suppression and on electrostatic properties of their membranes
The biological activity of copper nanoparticles, able to suppress growth of E. coli cells population under contact interactions, was explored. Three types of samples with oxide layers of various sizes, thickness and composition were used in experiments. It was found out, that an increase in electron density on the external membrane of E. coli correlated with copper nanoparticles suppression capability and with lower activation energy of electron transfer on bacteria. The analysis of experimental data helps to correct conditions for obtaining nanoparticles with certain properties of their surface oxide layers. The character of temperature dependence of electron density reveals the electron type of conductivity in contact area of E. coli and nano-particles. These results help to find approach to understanding the nature of toxic influence of copper nano-particles on E. coli cells under contact interaction.
Changes in the electric characteristics of the inner surface of Escherichia coli cytoplasmic membrane after the binding of microdoses of copper to its outer surface
The electric characteristics of the surface structures of intact Escherichia coli spheroplasts and the spheroplasts with the outer membrane modified by microdoses of copper were studied by electron spin resonance using the positively charged spin probes of KATn type and the newly synthesized KAT15. The experimental results were analyzed using the Gouy-Chapman formalism. It was found that microdoses of copper ions bound to the outer surface of the cytoplasmic membrane influenced the charge density on the inner surface of the membrane.
Non-protein components of the cell surface of Staphylococcus aureus.
1. pH-mobility curves of various laboratory strains of Staphylococcus aureus are non-sigmoid in shape, and all pass through a maximum value in the range pH4-5. 2. The maxima in the curves are not due to incomplete washing of the cells, adsorption of buffer components or irreversible surface damage. 3. Mild oxidation of the cell-surface teichoic acid with sodium metaperiodate gives cells that have typical sigmoid pH-mobility curves, characteristic of either a simple carboxyl surface or a mixed carboxyl-amino surface. 4. The results are discussed in terms of a pH-dependent change in the configuration of the teichoic acid molecules at the surface.