ID#: 23595
Caption:
This image depicts two test tubes containing nitrate broth. The tube on the left was inoculated with the fungal organism Cryptococcus neoformans, while the tube on the right was inoculated with C. terreus. This test determines whether the organism produces the enzyme nitrate reductase, which reduces nitrate (NO3) to nitrite (NO2). After the addition of the reagents a-naphthylamine and sulfanilic acid, the presence of nitrite is indicated by development of a pink to red color due to formation of an azo dye. C. neoformans does not produce nitrate reductase, and the broth remains colorless, whereas C. terreus produces the enzyme, resulting in a pink reaction.
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Content Provider(s): CDC/ Dr. Hilliard F. Hardin
Creation Date: 1967
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Copyright Restrictions: None - This image is in the public domain and thus free of any copyright restrictions.