The effect of surface characteristics on the sticking efficiency distribution of various environmental E : coli isolates

The attachment of biocolloid onto porous media is a complex process involvinggeochemistry, hydrochemistry and surface characteristics of microbes. In order to assessthe effects of cell surface characteristics (motility, zeta potential, hydrophobicity andantigen-43 expression) on the sticking efficiency distribution of Escherichia coli (E.coli) in saturated quartz sand, column experiments were conducted using six wellcharacterized environmental E. coli isolates. The total column length was 4.83 m, andtwo experiments were carried out for each isolate: in demineralized water (DW) and inartificial ground water (AGW). In each experiment, breakthrough concentrations weremeasured at various distances from the column inlet. We observed considerable interstrainvariation of sticking efficiency (upto1 log unit) between various E. coli isolates.The results in both DM and AGW showed decreasing sticking efficiencies along thetravel distance. Moreover, as a deviation from classical colloid filtration theory (CFT),the sticking efficiency was not a constant but distributed among the bio-colloidpopulation. We observed a very wide variation of the sticking efficiency (1.E-05 to 3.E-01) within the same E. coli population. This study showed that motility of E. coli cellsand expression of antigen 43 (Ag43) on the outer surface membrane of E. coli cellswere important properties affecting attachment, with both of them having a positivecorrelation with the sticking efficiency. However, no significant correlation wasobserved between sticking efficiency and zeta potential or hydrophobicity. This findingsuggested that less motile bacteria with little or no antigen 43 expression may travellonger distances, once they enter into groundwater environments