<i>E coli</i> Accumulation behind an Obstacle

Abstract

This paper describes our findings regarding the accumulation of motile bacteria at the rear of a confined obstacle and the physical description of the mechanisms at play. We found that the modification of flow due to the presence of the obstacle produces vorticity that favor the diffusion of bacteria towards the downstream stagnation point. By testing different flow rates, we determined the range in which bacteria accumulate. More interestingly, we observe that hydrodynamic interaction between the bacteria and the top and bottom surface of the microfluidic chip maintain the bacteria in the region where the flow velocity is lower than their own velocity. In the case of non-motile bacteria, this effect is not observed because bacteria follow the streamlines as passive tracers do.

The influence of motility on bacterial accumulation in a microporous channel

“…Our model for a microporous environment consists of a cylindrical obstacle placed under a microfluidic flow, mimicking the experimental setup of ref. 40. This geometry has been chosen because it contains the basic ingredients found in porous media: solid surfaces, velocities that vary along the stream lines, and stagnant flow zones (regions of low velocities).…”

The effect of flow on swimming bacteria controls the initial colonization of curved surfaces

“…Similarly, the ciliated epidermal surface of corals creates flows that stir the boundary layer, enhancing oxygen transport 26 and potentially affecting the transport of symbionts and pathogens. In these and many other scenarios, bacteria are recruited to surfaces that are not flat 14,15,[27][28][29] . Yet, despite its biological relevance, a mechanistic understanding of the interplay between flow and bacterial motility in the initial colonization of uneven and curved surfaces is so far missing.…”

“…The trapping is a hydrodynamic phenomenon, determined by the action of fluid shear on motile, elongated bacteria 12,13 . Bacterial accumulation also occurs in shallow microfluidic channels behind obstacles and after constrictions 14,15 and in curved channels downstream of corners, leading to the formation of suspended biofilm structures [16][17][18] . In groundwater, the size of the grains of the porous matrix 19,20 and the heterogeneity in flow velocities 20,21 affect the transport of colloids and, potentially, bacteria.…”

A comparative study between two models of active cluster crystals

“…In addition, it is well-known that active particles, also in the non-interacting case, manifest the tendency to accumulate near the walls 87,88 , in the regime of large persistence. Both for AOUP and ABP active forces, a microswimmer maintains its direction roughly during the active force correlation time (1/ D r or τ ).…”