Most experiments on the environmental factors affecting bacterial growth have been conducted on cells in the freely floating, planktonic state. However, bacteria often attach to surfaces and cavities to form dense colonies, or biofilms. The physical conditions in these communities are very different than those experienced by free-floating bacteria. In crowded environments, bacteria may experience increased competition for food, as well as mechanical pressures due to contact with their neighbors and the substrate. The hydration of the colony and surface tension also become important physical parameters which affect the physiology of the colony when grown on an air/solid nutrient boundary. I investigate these effects through experiments on colonies growing on two-dimensional substrates (agar gel) as well as simulations of colonies as a discrete collection of elastic cells, and as a continuum fluid.