Most growth models have been developed for a monoculture in a closed habitat — that is, for a single microbial “species” or strain in an isolated environment. A closed habitat means that life-sustaining resources, such as nutrients, are finite and no material or energy is exchanged with the outside. Such idealized systems must be quite rare in the context of foods, open water reservoirs, and pathogen multiplication inside or on a human’s body, especially if energy and gas exchange is considered. Yet, if material resource availability is the main factor that controls the microbial population growth rate, traditional models developed for a closed system can be quite adequate. Even if total isolation does not exist, the microbial growth pattern in an underprocessed can of ground meat or fish on a supermarket shelf, refrigerated milk during transportation, or standing water in a puddle or a storage tank, for example, is very different from the pattern found in an industrial fermentor or the human gut, where critical resources are continuously replenished and metabolites exuded by the growing organism are removed.