Czapek medium

Czapek medium, also called Czapek's agar (CZA)[1][2] or Czapek-Dox medium, is a growth medium for propagating fungi and other organisms in a laboratory. It was named after its inventors, Czech botanist Friedrich Johann Franz Czapek (May 16, 1868 – July 31, 1921) and American chemist Arthur Wayland Dox (September 19, 1882 – 1954). It was developed to grow Aspergillus niger[3] and Penicillium camemberti.[4] It works well for many saprophytic fungi and soil bacteria[5] such as species of Aspergillus, Candida, Penicillium, and Paecilomyces.[6]

Aspergillus bertholletius on Czapek agar

Aspergillus tubingensis growing on Czapek medium

Friedrich Czapek's original recipe is as follows:[3]

• 1000 g distilled water
• 30 g cane sugar – energy source and sole source of carbon[5]
• 1 g dipotassium phosphate – buffering agent[5]
• 0.5 g magnesium sulfate – source of cations[5]
• 0.5 g potassium chloride – source of essential ions[5]
• 0.01 g iron sulfate – source of cations[5]

Aspergillus fumigatus on Czapek agar

Arthur Wayland Dox added 2 g of sodium nitrate in his version, to provide a sole source of nitrogen that is inorganic.[4] This makes the medium a selective growth medium as only organisms that can use inorganic nitrogen can grow.[6] Czapek and Dox did not add agar but many recipes add 15 g to make a solid medium.[5][6]