What term refers to a liquid growth medium used in microbiology?

The term that refers to a liquid growth medium used in microbiology is broth. A broth is a nutrient solution that supports the growth of microorganisms, making it essential in the cultivation and experimentation of bacteria and other microbes. It provides the necessary nutrients, moisture, and pH balance required for the microorganisms to thrive.

In contrast, agar is a gelatinous substance derived from seaweed that is typically used as a solidifying agent in growth media rather than as a liquid medium itself. Gel refers more broadly to any semi-solid substance that might be used in various contexts but is not specifically defined as a growth medium in microbiology. Emulsion denotes a mixture of two immiscible substances, usually oil and water, and is not specifically related to microbial growth media. Thus, the choice of broth accurately describes the liquid medium used for growing bacterial cultures.