ID#: 16224
Description: Caption:
These two test tubes represented two different growth environments. The left tube contained a growth medium containing the amino acid phenylalanine (+), while the tube on the right contained no phenylalanine (-). This was a test to determine the presence, or absence of Gram-positive members of the family of bacteria, Enterobacteriaceae, which could, or could not enzymatically break down, or deaminate phenylalanine. Note that the left tube contents exhibited a greenish coloration, indicating the enzymatic deamination of the phenylalanine contained within, converting it to phenylpyruvic acid. The tube on the right contained a bacterium, though of the same family, could not deaminate, or break down the phenylalanine, and therefore, produced a yellow color, or a negative result.
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Content Providers(s): CDC/ Dr. William Howell Ewing
Creation Date: 1962
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Copyright Restrictions: None - This image is in the public domain and thus free of any copyright restrictions. As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image.