For surface cultivation of microorganisms, a sulfated polymer called agar can be extracted from and added to liquid media in order to cause it to solidify.

For surface cultivation of microorganisms, a sulfated polymer called agar can be extracted from algae and added to liquid media in order to cause it to solidify.

Explanation:

Agar can be described as a phycocolloid which is extracted from red-purple marine algae. Agar is typically used in a final concentration of 1-2% for solidifying culture media. Agar is isolated from the algae as an amorphous and translucent product sold as powder, flakes, or bricks. It is used for experiments such as gel electrophoresis and is an excellent medium for analzyzing DNA.