Overview

This test is used to determine the presence of oxidase enzymes. The reaction of oxidase is due to the existence of a cytochrome oxidase system that activates the oxidation of the cytochrome that is reduced by the molecular oxygen, which produces water or hydrogen peroxide according to the bacterial species. Therefore the oxygen acts like the final electron acceptor in the electron transport chain. In general, the cytochrome oxidase system is only found in the aerobic organisms, some facultative anaerobic organisms and, exceptionally, in some microaerophiles, although the strict anaerobes lack oxidase activity.

The presence of the cytochrome oxidase enzyme in the bacteria under analysis is investigated.

Carrying out the practical

Paper strips that have been impregnated with the reagent p-amino-n,n-dimethylaniline is used, which is oxidized by the cytochrome oxidase. The procedure consists in impregnating the colored area of the reagent strip with a mass of bacteria.

The impregnated area is observed for a minute to see whether it turns a blue-purple color.

oxidase – oxidase +

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