Defense Date


Graduation Date

Summer 8-13-2022


Immediate Access

Submission Type


Degree Name



Biological Sciences


Bayer School of Natural and Environmental Sciences

Committee Chair

Wook Kim

Committee Member

Nancy Trun

Committee Member

Jan Janecka

Committee Member

Michael Cascio

Committee Member

Vaughn Cooper


biofilm, mutation, Pseudomonas, cyclic di-GMP, signal transduction, experimental evolution


Microbial communities contain densely packed cells where competition for space and resources are fierce. These communities are generally referred to as biofilms and provide advantages to individual cells against immunological and antimicrobial intervention, dehydration, and predation. High intracellular pools of cyclic diguanylate monophosphate (c-di-GMP) cause cells to aggregate during biofilm formation through the production of diverse extracellular polymers. Genes that encode c-di-GMP catalytic enzymes are commonly mutated during chronic infections where opportunists display enhanced resistance to phagocytosis and antibiotics. Our lab uses an emergent multicellular trait in the model organism Pseudomonas fluorescens Pf0-1 to study the emergence of c-di-GMP mutations within biofilms. Here, two morphotypes repeatedly and bi-directionally evolve to spread out and conquer new territory together. The use of whole-genome sequencing, high-resolution microscopy, quantitative chemistry, and molecular engineering in this dissertation confirms that the multicellular trait manifests through c-di-GMP modulation. In the following chapters, I evaluate known c-di-GMP regulatory pathways, I analyze the genomes of 191 mutants generated through parallel evolution, and I explore the molecular consequences of c-di-GMP modulation. This dissertation identifies mutations in genes that are known, bioinformatically predicted, or not previously associated with c-di-GMP. Overall, this work demonstrates how an experimental evolution system can systematically map out many c-di-GMP regulatory switches and uncover new innovations through molecular evolution.



Additional Citations

Kessler C, Mhatre M, Cooper V, Kim W. (2021). Evolutionary divergence of the Wsp signal transduction system in β- and γ-proteobacteria. Applied and Environmental Microbiology, 87(22), e01306-21.