Effects of Phosphate on the Transport of Escherichia coli O157:H7 in Saturated Quartz Sand

Abstract

Consumption of groundwater contaminated with E. coli O157:H7 has led to several waterborne disease outbreaks over the past decade. A thorough understanding of the transport of E. coli O157:H7 within the soil-groundwater system is critical to the protection of public health. Although phosphate is ubiquitous in the natural environment, the influence of phosphate on the transport of E. coli O157:H7 in the groundwater system remains unknown. In this research, we performed column transport experiments to evaluate the effect of phosphate on the transport of E. coli O157:H7 cells within saturated sand. The pH of the solutions was maintained at 7.2, the ionic strength varied from 10 to 100 mM, and the phosphate concentration ranged from 0 to 1 mM. Our results show that (1) phosphate could enhance the transport of E. coli O157:H7 cells under both ionic strength conditions; (2) E. coli O157:H7 displayed lower retention in sand under higher ionic strength conditions; (3) increased phosphate in the mobile aqueous phase led to the release of previously immobilized E. coli O157:H7 cells. The response of E. coli O157:H7 cells to variations in phosphate concentrations and ionic strength conditions are explained using the extended DLVO (XDLVO) theory and the steric repulsion caused by extracellular macromolecules. In summary, our results suggest that phosphate could widen the spread of E. coli O157:H7 cells, and potentially other types of bacterial cells, within the soil-groundwater system.

Blocking effect of colloids on arsenate adsorption during co-transport through saturated sand columns

“…But, at pH 9.8, soil colloid was difficult to deposit into the primary energy minimum due to the high primary energy barrier (>250 kT). The retention of the soil colloids at pH 9.8 possibly occurred mainly through their entrapment within the secondary energy minimum (Feriancikova et al, 2013;Wang et al, 2011b), where the soil colloid is easily removed by kinetic energy of diffusing (Fig. 4b).…”

Dual Roles of Capsular Extracellular Polymeric Substances in Photocatalytic Inactivation of Escherichia coli: Comparison of E. coli BW25113 and Isogenic Mutants

“…The XDLVO theory was used to model the interaction between bacterial cells and TiO 2 nanoparticles. This theory considers the total energy of adhesion to be the sum of the electrostatic double layer (EL) interaction energy, the Lifshitz-van der Waals (LW) interaction energy, and the Lewis acid-base (AB) (i.e., hydrophobic) interaction energy (36)(37)(38)(39). Details of these procedures are described in the supplemental material.…”

“…S8 in the supplemental material) (38). Zeta potential measurements reveal that these three strains were all negatively charged, whereas TiO 2 was positively charged at the test pH (6.5) of the photocatalytic treatment, indicating an attractive EL interaction between the bacterial cells AB values for the bacterium-water-TiO 2 system for the wild type, the cpsB mutant, and the rcsC mutant were Ϫ2.25, 1.81, and Ϫ3.60 mJ/m 2 , respectively, indicating that the presence of capsular EPS favored an attractive interaction between TiO 2 nanoparticles and bacterial cells, while the absence of capsular EPS resulted in a repulsive AB interaction.…”

Comparison of the transport of Bacteroides fragilis and Escherichia coli within saturated sand packs

“…It is well known that many factors, such as surface macromolecules, cell and grain roughness, and surface charge heterogeneity that are not considered by the XDLVO theory, can play important roles in cell immobilization [34][35][36][37]. As suggested by several recent studies [38,39], further research that aims at quantifying and distinguishing the effects of such factors is warranted.…”