Microbial communities drive processes ranging from human health to global nutrient cycling. Furthermore, there is great hope that the power of microbial consortia can be harnessed to generate biofuels and novel pharmaceuticals. Despite the clear importance of microbes we remain largely ignorant about how the physiology and ecological interactions of cells shape the content, function and evolutionary dynamics of microbial communities. The Harcombe lab uses synthetic communities to mechanistically dissect the interplay between ecological and evolutionary processes across multiple levels of biological organization. Additionally, we use computational approaches to quantitatively investigate how the behavior of metabolic networks influences the emergent properties of complex systems from cells to ecosystems.