Colonies of microorganisms that adhere to environmental surfaces are called ____________.

The term describing colonies of microorganisms that adhere to environmental surfaces is "biofilms." Biofilms are structured communities of microorganisms, primarily bacteria, that attach to surfaces and are embedded in a protective extracellular matrix. This matrix allows them to thrive in various environments and protects them from harsh conditions, including antimicrobial treatments.

Biofilms play significant roles in both natural and artificial environments, such as in plumbing systems, medical devices, and even our own bodies. Understanding biofilms is crucial in cosmetology and hygiene because they can influence the effectiveness of sterilization procedures and the spread of infections.

The other options, while related to the study of microorganisms, do not accurately represent colonies that adhere to surfaces. Bacteria form the individual units within biofilms, but alone they do not describe the collective structure. Viruses are distinct entities that do not form biofilms, as they require a living host cell to replicate. Spores are a form of reproduction or survival for some microorganisms but do not pertain to the concept of adhering colonies. Thus, "biofilms" is the most precise term for describing these microbial arrangements.