2) Oxidase Test: The oxidase test is a means of specifically detecting the presence of the terminal enzyme system in aerobic respiration called Cytochrome C oxidase. The aerobic respiratory mechanism is composed of a number of enzymes which alternately oxidize & reduce each other by donating or accepting electrons derived from hydrogen. Hydrogen atoms are removed from various substrate compounds during oxidation reaction & ultimately the hydrogen atoms are combined with oxygen to form water. Thus, cytochrome C oxidase is the terminal or last hydrogen electron acceptor in this chain, its function being to transfer the hydrogen electrons to oxygen to form water molecules. This is the classic aerobic respiration scheme that most microorganisms utilize to derive energy from the food they take in as molecules of ATP.
The ability of an organism to produce cytochrome C oxidase can be determined by using the reagent tetramethyl-p-phenylenediamine. This reagent serves as an artifical substrate donating electrons & thereby becoming oxidized to blackish compound in the presence of the enzyme oxidase & free oxygen.
The members of Enterobacteriaceae give negative result whereas Pseudomonas spp, Aeromonas spp, Vibrio spp, Neisseria spp, etc give positive result.
Fig: Oxidase Test
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Cited By Kamal Singh Khadka
Assistant Professor In Pokhara University, Regional college of Science & Technology, PNC, NA