What is produced by adding 1% to 5% agar to nutrient broth that is then boiled and cooled?

Adding 1% to 5% agar to nutrient broth results in the formation of a solid medium once the mixture is boiled and allowed to cool. Agar is a gelatinous substance derived from seaweed and is commonly used as a solidifying agent in microbiological media. When agar is heated, it dissolves, creating a liquid medium. As the mixture cools, the agar sets and forms a solid surface on which microorganisms can grow. This solid medium provides stability and a firm surface for culturing organisms, which is essential for a variety of microbiological applications, such as isolating colonies and performing various assays.

In contrast, a gaseous medium would imply a state where the medium is primarily in vapor form, which doesn’t apply in this scenario. A liquid medium would mean the absence of agar solidification, leaving the broth in a fluid state. A colloidal suspension might suggest a mixture where particles are dispersed, but in this case, the agar solidifies to create a firm, stable medium rather than remaining in suspension. Hence, the introduction of agar to the nutrient broth and subsequent cooling leads to the creation of a solid medium ideal for microbiological study.