Correlating Transport Behavior with Cell Properties for Eight Porcine Escherichia coli Isolates

Abstract

In this study we investigate how growth stage and depositional environment affect variability of cell properties and transport behavior of eight porcine E. coli isolates. We compared the surface properties for cells harvested during exponential and stationary growth phase and their transport behavior through columns packed with either uncoated or Fe-coated quartz sand. We then investigated correlations between measured cell properties and fitted bacterial attachment efficiencies. For both growth stages we found that bacterial attachment efficiencies in the uncoated quartz sand varied among the eight different isolates by over an order of magnitude whereas attachment efficiencies in the Fe-coated sands varied by a factor of less than two. With the exception of one isolate, growth condition had minimal impact on attachment efficiencies to the uncoated sands. A strong and statistically significant inverse relationship was observed between bacterial attachment efficiencies in the uncoated quartz sand columns and log-transformed zeta potential, whereas a mild yet statistically significant relationship between bacterial attachment efficiencies in the Fe-coated sands and cell width was observed. For the experimental conditions used in our study, we found that variability in E. coli transport was more dependent on the depositional environment than on growth conditions.

Transport of multiple Escherichia coli strains in saturated porous media

“…Such observed sticking efficiency homogeneity is in sharp contrast with our previous works Lutterodt et al, 2009a,b) and observations made by other workers (Schinner et al, 2010;Yang et al, 2008;Bolster et al, 2009Bolster et al, , 2010, who observed significant variations in transport among the various E. coli strains used in their experiments. Though it is difficult to explain such observed homogeneity from E. coli surface characteristics (Table 7.3), the strains used in this work were isolated from flow lines at their termination points (springs), and such strains may therefore possess certain cell characteristics that might have influenced their selective transport in the subsurface giving rise to their similar transport characteristics in our columns.…”

“…However, all studies, aimed at revealing sticking efficiency distributions, have been conducted for limited transport distances (centimeter to decimeter), and can therefore not be considered representative for longer transport distances, which are so important in microbial risk assessment of groundwater and therefore in quantifying the potential health impacts of pathogenic microorganisms traveling in aquifers. In addition, experiments that focussed on studying the effects of cell properties on their attachment to quartz grains have been conducted at short transport distances (<0.5 m) for limited number of strains (< 20 strains) (Becker et al, 2004, Bolster et al, 2010, Levy et al, 2007. Important questions still remaining are: How low can the sticking efficiency of fractions of cells within a population be?…”

“…Due to the importance of E. coli, considerable attention has been given to understanding their transport and fate in saturated porous media (e.g. Foppen et al, 2006, Schinner et al, 2010, Bolster et al, 2010. In most of these studies, bacteria strains isolated from different sources, for example from zoo animals , a swine lagoon (Bolster et al, 2010), a dairy cow manure and sewerage (Haznedaroglu et al, 2008), or a soil of a pasture used for cattle grazing , Lutterodt et al, 2009a, b, Yang et al, 2008 were used.…”

“…Foppen et al, 2006, Schinner et al, 2010, Bolster et al, 2010. In most of these studies, bacteria strains isolated from different sources, for example from zoo animals , a swine lagoon (Bolster et al, 2010), a dairy cow manure and sewerage (Haznedaroglu et al, 2008), or a soil of a pasture used for cattle grazing , Lutterodt et al, 2009a, b, Yang et al, 2008 were used. To our knowledge, there is no study reported in the literature that focuses on the transport of E. coli strains isolated after they Transport of multiple Escherichia coli Transport in saturated porous media 86 have undergone transport in an aquifer.…”

“…Due to the importance of E. coli, considerable attention has been given to understanding their transport and fate in saturated porous media (e.g. Foppen et al, 2007a,b, Schinner et al, 2010, Bolster et al, 2010. This thesis is looking into more detail at the transport of E. coli in saturated porous media.…”