EFFECTS OF ENTEROCOCCAL SURFACE PROTEIN (ESP) ON THE TRANSPORT OF ENTEROCOCCUS FAECIUM WITHIN SATURATED AQUIFER SANDS

In this research, we examine the effects of enterococcal surface protein (esp) on the transport of Enterococcus faecium within the groundwater system. An E. faecium strain derived from human sources and the corresponding esp negative mutant were used. A series of column transport experiments were performed using buffered (pH = 7.2) electrolyte solutions (ionic strength: 1-50 mM) to quantify their retention within saturated quartz sands. Our results showed that esp could significantly enhance the retention of E. faecium within saturated aquifer sands. The surface properties of the E. faecium cells were then determined and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) model was then applied to examine the energy interaction profiles between the E. faecium cells and the surface of the quartz sands, which could strongly influence the deposition kinetics of the bacterial cells. Findings from this research suggested that E. faecium derived from human sources, a high percentage of which tends to contain esp, could have lower mobility within the groundwater system than E. faecium derived from non-human sources. This finding also has important implications for the potentail use of esp as a groundwater microbial source tracking tool.