In partial fulfillment of the requirements for the degree of 

Doctor of Philosophy in Quantitative Biosciences

in the School of Physics

Pablo Bravo

Defends his thesis:

Topographic Characterization of Biofilm Growth

Tuesday, May 21, 2024 

10:00 am ET 

Howey N201/202

https://gatech.zoom.us/j/98166092376?pwd=NnhRd2hMQUxMTzZvdktmUmY4UjEyUT09

Advisor:

Peter Yunker, School of Physics, Georgia Institute of Technology

Committee Members:

Brian Hammer, School of Biological Sciences, Georgia Institute of Technology

Jennifer Curtis, School of Physics, Georgia Institute of Technology

Sam Brown, School of Biological Sciences, Georgia Institute of Technology

Itamar Kolvin, School of Physics, Georgia Institute of Technology

Abstract:

Biofilms are ubiquitous in nature and have significant impacts on ecosystems, human health, and various industries. However, their complex three-dimensional structure and heterogeneous composition pose challenges for accurate measurements and modeling. Using white light interferometry, we measure the heights of microbial colonies with nanometer precision from inoculation to their final equilibrium height, producing a detailed empirical characterization of the biofilm-air interface. We characterized universal dynamics in the vertical growth defined by two regimes: exponentially early on until a given thickness, and then growth decreases linearly until it stops. We propose a simple model based on the formation of a finite-size growth layer, which captures the dynamics over short and long timescales. Furthermore, we observed that the biofilm-air interface exhibits a unique topographic "freezing" phenomenon, previously undescribed in physics and biology, that makes biofilms smoother than polished steel. We postulate that this freezing, even when colonies are still developing, is a product of mechanical damping of fluctuations that arise from the finite-size growth layer across the growing colony. These studies provide a foundation for understanding the complex spatiotemporal dynamics of biofilms via precise measurements of their topographies. This interdisciplinary work combines cutting-edge experimental techniques with physically-motivated models to uncover fundamental aspects of biofilm physiology. The findings contribute to our basic understanding of microbial communities and have potential implications for diverse applications in healthcare, biotechnology, and environmental science.