Evolving Better Biofilms: The Dynamics of Community-Level Natural Selection in Bacteria

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This project addresses the evolution of multi-species communities using both bacterial and computational model systems. Biofilms are assemblages of bacteria that adhere to surfaces, both living and nonliving, and to each other. They are often composed of multiple species and cause human diseases, contaminate medical and food production equipment, corrode pipes, purify polluted waters, and protect materials from degradation. In this project, communities of species will be selected both in vitro and in silico to produce biofilms that are stronger and more resistant to parasites, antibiotics and/or caustic chemicals. These experiments will illuminate the effects of species composition and diversity on the evolution of a successful community.Natural selection not only favors fit organisms but also can act at a higher level, favoring entire populations over others, a process known as group selection. In multi-species bacterial infections, combinations of species that form stable, transmissible infections will successfully proliferate to new hosts, and will thereby be favored as an entire assemblage for further evolution. In cheese production and wastewater decontamination, dairy producers and environmental engineers artificially select among mixed communities of bacteria for those that perform these tasks best. What allows mixed communities to solve some ecological problems better that homogeneous communities? Does community-level evolution follow the same principles as individual-level evolution? Although mixed microbial communities underlie many health and environmental concerns, virtually nothing is known about their evolution. Because biofilms thrive in nature as both monocultures and mixed cultures, they offer an ideal test bed for exploring the fundamentals of community-level selection.