Why is agar used when scientists grow bacteria for plaque assays?

Agar is used in plaque assays because it serves as a solidifying agent for bacterial culture media. When mixed with nutrients, agar creates a solid surface within a petri dish, known as an agar plate. This solid medium allows scientists to grow bacteria and observe the formation of plaques, which are clear areas indicating the presence of an antibacterial factor. Agar's unique property is its ability to form a firm gel at body temperature (37°C or 99°F), providing a stable environment for bacterial growth and plaque visualization.123