Bacterial floc mediated rapid streamer formation in creeping flows

TL;DR

This study uncovers a rapid formation mechanism of bacterial streamers from flocs in creeping flows, revealing their elastic properties and impact on microfluidic clogging, distinct from traditional biofilm-mediated streamers.

Contribution

It introduces a new type of bacterial streamer formation from flocs in low Reynolds number flows, occurring within seconds and characterized by elasticity and dynamic behavior.

Findings

Streamers form within less than a second from bacterial flocs.

Formed streamers exhibit significant elastic deformation.

Rapid streamer formation can cause quick clogging in microfluidic devices.

Abstract

One of the central puzzles concerning the interaction of low Reynolds number (Re<<1) fluid transport with bacterial biomass is the formation of filamentous structures called streamers. In this manuscript, we report our discovery of a new kind of low Re bacterial streamers, which appear from pre-formed bacterial flocs. In sharp contrast to the biofilm-mediated streamers, these streamers form over extremely small timescales (less than a second). Our experiments, carried out in a microchannel with micropillars rely on fluorescence microscopy techniques to illustrate that floc-mediated streamers form when a freely-moving floc adheres to the micropillar wall and gets rapidly sheared by the background flow. We also show that at their inception the deformation of the flocs is dominated by recoverable large strains indicating significant elasticity. These strains subsequently increase tremendously to produce filamentous streamers. Interestingly, we find that these fully formed streamers are not static structures and show viscous response at time scales larger than their formation time scales. Finally we show that such novel streamer formation can lead to rapid clogging of microfluidic devices.