Effects of Polymer on the Behavior of Bacterial Suspensions

Abstract

Bacterial motility and behavior in polymer environments is relevant to a number of real world situations, from the microbiome to cystic fi brosis infections. Suspensions of bacteria and their interactions with oxygen and nutrient gradients have been examined in the past, but polymer has been absent from these studies. We explore the effects of polymer on bacterial suspensions by imaging a small droplet of bacteria in polymer between two glass surfaces. We find that polymer introduces wave-like instabilities between the motile and immotile regions of the sample. We also fi nd that the immotile core of bacteria, formed by a lack of access to oxygen beyond a certain distance due to an oxygen gradient, shrinks over time and evaluate various hypotheses to explain this phenomenon. We fi nd that the most likely explanation may be that the oxygen demands of the bacteria change over time.