Cargo carrying bacteria at interfaces

Abstract

The displacements of ensembles of colloids at the interface between oil and suspensions of the bacterium Pseudomonas aeruginosa PA14ΔpelA indicate enhanced colloid mobilities and apparently diffusive motion driven by interactions with the bacteria. However, inspection of individual trajectories of ∼500 particles reveals prolonged, directed displacements inconsistent with purely hydrodynamic interactions between swimming bacteria and colloids. Analysis of the properties of colloid paths indicates trajectories can be sorted into four distinct categories, including diffusive, persistent, curly, and mixed trajectory types. Non-diffusive trajectories are the norm, comprising 2/3 of the observed trajectories. Imaging of colloids in the interface reveals anisotropic assemblies formed by colloids decorated with one or more adhered bacteria that drive the colloids along these paths. The trajectories and enhanced transport result from individual colloids being moved as cargo by these adhered bacteria. The implications of these structures and open questions for interfacial transport are discussed and related to the active colloid literature.

Particle diffusion in extracellular hydrogels

“…[26][27][28] We complement the ensemble-averaged information obtained from DDM with single particle tracking, using the same time-lapse imaging data as input, in order to test for the presence of spatial and temporal heterogeneities in particle dynamics that typically arise in heterogeneous systems such as polymer gels. [29][30][31][32] In order to understand how the dynamics of hyaluronan networks are modulated by accessory extracellular molecules that introduce crosslinks, we probe singlecomponent gels with three different crosslink configurations: semidilute solutions, transiently crosslinked gels obtained by pH-triggered gelation, 33 and chemically crosslinked gels. We show that semidilute solutions and transiently crosslinked hyaluronan networks simply hinder particle transport through enhanced viscous drag, whereas permanently crosslinked gels hamper particle diffusion by size exclusion.…”

Living Materials Herald a New Era in Soft Robotics

“…With this light-driven process, the motion of bacteria is regulated by the intensity of light and speed can be changed by illumination intensity. [19f ] Furthermore, also micrometer-sized objects can by driven in biohybrid systems, as recently shown for the bacterial transport of colloidal particles on oil interfaces [106] and in electropolymerized microtubes. [107] Such "micro-biohybrid" devices appear to be suited for miniaturized transport applications.…”

Driven and active colloids at fluid interfaces

“…More complex biohybrid colloids of P. aeruginosa adhered to polystyrene microbeads also exhibit a wide range of persistent, complex motions at fluid interfaces (Vaccari et al. 2018). On interfaces with surface tensions typical for alkane–aqueous systems, like those considered here, contact-line pinning significantly constrains the motion of driven and active colloids.…”