UC San Diego

Bacteria are widespread on Earth. They play important roles in shaping the global ecosystems as well as influencing human health. In nature, different bacterial species often coexist in a common environment. The interactions of them are diverse and often lead to intricate spatial-temporal dynamics. Quantitative experimental measurements as well as mathematical modeling could help us better understand the mechanisms behind such dynamics. In this dissertation, I discuss several spatial-temporal structures for multi-strain bacterial systems and different modeling strategies are used to help explore the mechanisms of different spatial-temporal patterns. A key question regarding a system of different bacterial species is how coexistence is maintained, considering that different bacterial species often have different growth rates and they can even kill each other sometimes. In Chapter Two, I discuss a novel theoretical framework for robust coexistence and pattern formation in bacterial mixtures with contact-dependent killing. In Chapter Three, I present a beautiful spatial flower-like pattern in two-species bacterial systems from experiments and build two different models, a discrete interface model and a phase-field model, to elucidate how differential motility and mechanical interactions between bacterial species can create complex spatial structures. In Chapter Four, I introduce the agent-based modeling, which simulates each individual bacterial cell in large populations. Two examples of applications of such agent-based modeling in microfluidic environments are described. All these chapters combine to highlight the effort towards understanding the spatial-temporal dynamics of multi-strain microbial systems quantitatively.