Bacterial genes and genome dynamics in the environment

Abstract

One of the most marvelous features of microbial life is its ability to thrive in such diverse and dynamic environments. My scientific interest lies in the variety of modes by which microbial life accomplishes this feat. In the first half of this thesis I present tools to leverage high throughput sequencing for the study of environmental genomes. In the second half of this thesis, I describe modes of environmental adaptation by bacteria via gene content or gene expression evolution. Associating genes' usage and evolution to adaptation in various environments is a cornerstone of microbiology. New technologies and approaches have revolutionized this pursuit, and I begin by describing the computational challenges I resolved in order to bring these technologies to bear on microbial genomics. In Chapter 1, I describe SHE-RA, an algorithm that increases the useable read length of ultra-high throughput sequencing technologies, thus extending their range of applications to include environmental sequencing. In Chapter 2, I design a new hybrid assembly approach for short reads and assemble 82 Vibrio genomes. Using the ecologically defined groups of this bacterial family, I investigate the genomic and metabolic correlates of habitat and differentiation, and evaluate a neutral model of gene content. In Chapter 3, I report the extent to which orthologous genes in bacteria exhibit the same transcriptional response to the same change in environment, and describe the features and functions of bacterial transcriptional networks that are conserved. I conclude this thesis with a summary of my tools and results, their use in other studies, and their relevance to future work. In particular, I discuss the future experiments and analytical strategies that I am eager to see applied to compelling open questions in microbial ecology and evolution.