Drygalski's culture medium, also known as Conradi-Drygalski's medium, is a culture medium used for the isolation and identification of microorganisms, particularly E. coli. It was developed by German bacteriologists Friedrich Drigalski and Conradi at the beginning of the 20th century.
Drigalski's medium consists of peptone, lactose, bile, crystal violet dye and agar. Bile and crystal violet inhibit the growth of gram-positive bacteria, allowing the growth of predominantly gram-negative bacteria, such as E. coli. As E. coli grows, lactose is fermented to form acid, causing the color of the medium to change from purple to yellow. This makes it easy to identify E. coli growth.
Thus, Drygalski's culture medium is a useful tool for the isolation and identification of Escherichia coli and other gram-negative bacteria. It is widely used in microbiology laboratories and is important for the diagnosis of intestinal infections.