In microbiology, a preparation containing multiple species or strains of microorganisms is termed a mixed population. This contrasts with a pure population, which contains only a single type of organism. An example includes a sample of soil, where numerous bacteria, fungi, and other microorganisms coexist and interact within the same environment.
The examination of these diverse populations is crucial for understanding complex biological processes such as nutrient cycling in ecosystems, the development of biofilms, and the dynamics of microbial communities in various environments, including the human gut. Studying them allows researchers to model interactions between species, observe synergistic relationships, and gain insights into the overall functionality of complex ecological systems. Early research into microbial interactions relied heavily on observations within these populations, leading to the discovery of phenomena like antibiotic resistance transfer and quorum sensing.