Abstract

Microbes inhabit planet earth over billions of years and have adapted to diverse physical environments, particularly at or near fluid boundaries. A uni-flagellated bacterium, Caulobacter crescentus, is a species of choice by microbiologists to study cell differentiation and genetic regulation. From the perspective of fluid and surface physics, I will discuss our study on the motility of C. crescentus swarmer cells in both viscous and visco-elastic media, their accumulation and motility near solid surfaces, and their behavior at an air/water interface. Specifically, I will describe both physical effects and surface chemistry that cause the motile cells to become trapped near the air/water boundary, and strategies the cells can employ to free themselves. I will also highlight the complex fluid mechanics required to predict the bacterial swimming speed in viscoelastic media.

The broader goal of our study is to elucidate interfacial microbial functions through microscopic imaging, data analysis, mathematical modeling, and computer simulations based on fluid physics. By understanding the mechanisms diverse species of motile bacteria have adopted through the course of evolution, we seek to gain insights useful towards environmental and biomedical applications.