OXIDASE TEST 1Think about theadvice given in the procedure t

OXIDASE TEST

1.Think about theadvice given in the procedure to test a known oxidase-positive organism along with an unknown. a.) Is this a positive or a negative control? b.) What information is provided by the results?

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Solution

Ans:

It advisable to include a known oxidase-positive control in any test of an unknown organism. Because

The oxidase test determines whether or not an organism has cytochrome oxidase in its electron transport chain. We can test by adding a drop of oxidase reagent (p-phenylenediamine) to the culture.

The Oxidase test (also known as the Cytochrome Oxidase test) is used to look for oxidase enzymes produced by Organism. Oxidases catalyse electron transport between substrates acting as electron donors in the bacterium and tetramethyl-p-phenylenediamine OR dimethyl-p-phenylenediamine - a redox dye present as the hydrochloride or oxalate salt (the latter has a longer shelf-life). The dye is reduced to a deep violet-blue colour in the presence of oxidase enzymes.

Usually the oxidase reagent contains a chromogenic reducing agent, which is a compound that changes color when it becomes oxidized. If the test organism produces cytochrome oxidase, the oxidase reagent will turn blue or purple within 15 seconds.

Here the control is a positive control

Conclusion: The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain. When present, the cytochrome c oxidase oxidizes the reagent (tetramethyl-p-phenylenediamine) to (indophenols) purple color end product. When the enzyme is not present, the reagent remains reduced and is colorless.