Characterizing the Transport and Surface Affinity of Extracellular Vesicles Isolated from Yeast and Bacteria in Well-Characterized Porous Media

Abstract

Extracellular vesicles (EVs) are membrane-bounded, nanosized particles, produced and secreted by all biological cell types. EVs are ubiquitous in the environment, operating in various roles including intercellular communication and plant immune modulation. Despite their ubiquity, the role of EV surface chemistry in determining transport has been minimally investigated. Using the zeta (ζ)-potential as a surrogate for surface charge, this work considers the deposition of EVs from the yeast, Saccharomyces cerevisiae , and two bacterial species, Staphylococcus aureus and Pseudomonas fluorescens , in well-characterized porous medium under various background conditions shown to influence the transport of other environmental colloidal particles: ionic strength and humic acid concentration. The affinity of S. cerevisiae EVs for the porous medium (glass beads) appeared to be sensitive to changes in ionic strength, as predicted by colloid stability (Derjaguin, Landau, Verwey, and Overbeek or DLVO) theory, and humic acid concentration, while P. fluorescens EVs deviated from DLVO predictions, suggesting that mechanisms other than charge stabilization may control the deposition of P. fluorescens . Calculations of attachment efficiency from these deposition studies were used to estimate EV transport using a clean-bed filtration model. Based on these calculations, EVs could be transported through such homogeneous porous media up to 15 m.

Extracellular Vesicles and Bacteriophages: New Directions in Environmental Biocolloid Research

“…In addition, the interaction energies between two vesicles were modeled from DLVO theory, although these predictions did not always mirror the experimental results. Describing an analogous colloidal process, Rogers et al examined the deposition of EVs from S. cerevisiae , S. aureus , and P. fluorescens by means of column studies . EVs from S. cerevisiae were transported as DLVO theory would predict, showing increased deposition with increasing ionic strength.…”

“…Describing an analogous colloidal process, Rogers et al examined the deposition of EVs from S. cerevisiae, S. aureus, and P. f luorescens by means of column studies. 109 EVs from S. cerevisiae were transported as DLVO theory would predict, showing increased deposition with increasing ionic strength. Furthermore, S. cerevisiae EV deposition was decreased in the presence of humic acid, as predicted, due to steric stabilization.…”

“…134 Moreover, multiple reports discuss the ability of EVs to transport cargo long distances, ranging from a few micrometers in cell culture to tens of meters in the natural environment, implying that organically produced membrane vesicles may be created to persist in environments in order to travel long distances to their target location. 109,135,136 Investigating the persistence of EVs could reveal unique discoveries regarding their purposes in the environment. More broadly, through studying the colloidal properties of EVs in the various environmental systems in which they exist, we can better understand the processes by which they disperse through these systems.…”

“…While some methods may not translate well, since protocols for largely inorganic NMs may not work for organic EVs, methods for the surface characterization of EVs as colloidal particles could be adapted for vesicles. Some studies have already explored these properties of EVs, − but this should be studied more widely, exploring a more extensive range of organisms’ EVs in different environmental conditions.…”