Linking bacteria-metal interactions to mineral attachment: A role for outer sphere complexation of cations?

In this study, we conducted attachment experiments and electrophoretic mobility titrations to investigate the mechanisms of attachment of Escherichia coli K12 onto quartz surfaces. Attachment experiments were performed as a function of pH in 0.01 M KNO3 and in the presence of 0.01 M Ca. Scanning electron microscopy and optical density measurements at 600 nm indicate significant pH dependant attachment of E. coli onto quartz surfaces. Electrophoretic mobility experiments performed as a function of pH in 0.01 M KNO3 with and without Ca demonstrated that the magnitude of the zeta potential decreased with the introduction of Ca for E. coli, but had little effect on the surface properties of quartz. These results indicate that the association of hard acid divalent cations with bacterial cells walls may influence the mechanisms and extent of their attachment onto mineral surfaces.