The role of zeta potential in the adhesion of E. coli to suspended intertidal sediments

Abstract

The extent of pathogen transport to and within aquatic systems depends heavily on whether the bacterial cells are freely suspended or in association with suspended particles. The surface charge of both bacterial cells and suspended particles affects cell-particle adhesion and subsequent transport and exposure pathways through settling and resuspension cycles. This study investigated the adhesion of Faecal Indicator Organisms (FIOs) to natural suspended intertidal sediments over the salinity gradient encountered at the transition zone from freshwater to marine environments. Phenotypic characteristics of three E. coli strains, and the zeta potential (surface charge) of the E. coli strains and 3 physically different types of intertidal sediments was measured over a salinity gradient from 0 to 5 Practical Salinity Units (PSU). A batch adhesion microcosm experiment was constructed with each combination of E. coli strain, intertidal sediment and 0, 2, 3.5 and 5 PSU. The zeta potential profile of one E. coli strain had a low negative charge and did not change in response to an increase in salinity, and the remaining E. coli strains and the sediments exhibited a more negative charge that decreased with an increase in salinity. Strain type was the most important factor in explaining cell-particle adhesion, however adhesion was also dependant on sediment type and salinity (2, 3.5 PSU > 0, 5 PSU). Contrary to traditional colloidal (Derjaguin, Landau, Vervey, and Overbeek (DLVO)) theory, zeta potential of strain or sediment did not correlate with cell-particle adhesion. E. coli strain characteristics were the defining factor in cell-particle adhesion, implying that diverse strain-specific transport and exposure pathways may exist. Further research applying these findings on a catchment scale is necessary to elucidate these pathways in order to improve accuracy of FIO fate and transport models.

The effect of cyclic variation of shear stress on non‐cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’

“…The increased adhesion may partly be due to the plentiful binding sites provided by the remaining organic matter attached to or between sediment particles and therefore surfaces are more available for microbes to adhere. A similar mechanism has been reported in a previous study on the role of cell and particle characteristics in the adhesion of Escherichia coli bacteria to suspended intertidal sediments (Wyness et al, 2018). This work showed that all strains examined adhered more efficiently to organic sediments than other abiotic sediment (i.e.…”

“…The physical disturbance by hydrodynamic forces cannot remove all organic material in sedimentary systems, i.e. A similar mechanism has been reported in a previous study on the role of cell and particle characteristics in the adhesion of Escherichia coli bacteria to suspended intertidal sediments (Wyness et al, 2018). As a result, bio-aggregates are introduced when they enter a water column (Figure 9).…”

Rainfall-driven E. coli transfer to the stream-conduit network observed through increasing spatial scales in mixed land-use paddy farming karst terrain

“…For smaller events (e.g. Event 3: <5.0 mm), the lack of response in E. coli concentration with increasing scale above the headwater catchments could be due to a lack of proximal, hydrologically connected sources, but also attenuation of E. coli by processes such as attachment to sediment particles and settling in stream bed sediments as the hydraulic gradient, and hence stream flow velocity, decreases (Schiperski et al., 2016; Wyness et al., 2018).…”

Activation of the type 3 secretion system of enteropathogenicE. colileads to remodeling of its membrane composition and function

“…Zeta potential was calculated using the Smoluchowski model. Data acquisition from 15 events was recorded for every sample, and the average Zeta potential was determined from four replicates (56).…”