The Moeller decarboxylase test is dependent upon which condition?

The Moeller decarboxylase test is dependent upon which condition?

• A. An alkaline pH shift in the medium
• B. The oxidation of gluconate
• C. An acid pH basal medium
• D. A deamination of tryptophan

Answer: (A)

The Moeller decarboxylase test works by detecting alkaline products produced when a cell with decarboxylase activity removes a carboxyl group from an amino acid. The medium is set acidic first (to allow color change if there’s no decarboxylation), and if the organism has the decarboxylase enzyme, it decarboxylates the amino acid under the anaerobic conditions created by an oil overlay, producing alkaline amines. That rise in pH shifts the indicator color to purple, indicating a positive result. So the test depends on an alkaline pH shift in the medium to reveal decarboxylase activity. The other options don’t drive the characteristic color change: oxidation of gluconate isn’t part of this assay, maintaining only an acidic basal state wouldn’t show decarboxylase activity, and deamination of tryptophan relates to different tests altogether.

The Moeller decarboxylase test works by detecting alkaline products produced when a cell with decarboxylase activity removes a carboxyl group from an amino acid. The medium is set acidic first (to allow color change if there’s no decarboxylation), and if the organism has the decarboxylase enzyme, it decarboxylates the amino acid under the anaerobic conditions created by an oil overlay, producing alkaline amines. That rise in pH shifts the indicator color to purple, indicating a positive result. So the test depends on an alkaline pH shift in the medium to reveal decarboxylase activity. The other options don’t drive the characteristic color change: oxidation of gluconate isn’t part of this assay, maintaining only an acidic basal state wouldn’t show decarboxylase activity, and deamination of tryptophan relates to different tests altogether.