bacteria possess a defence mechanism which can minimize the harm done by the two compounds. These resistant bacteria use two
enzymes to catalyze the conversion of hydrogen peroxide into diatomic oxygen and water. One of these enzymes is catalyse and
its presence can be detected catalyse test which involves adding hydrogen peroxide to a culture sample or agar slant. If the
bacteria produce catalyse, they will convert the hydrogen peroxide and oxygen gas will be evolved. The evolution of gas causes
bubbles to form and is indicative of a positive test.
Procedure to carry out Catalase test:
- Tube or bottle method
- Place 0.2 mL of hydrogen peroxide solution in a test tube
- Pick a colony to be tested with straight loop
- Rub the colony onto the inside wall of the bottle above the surface of the hydrogen peroxide solution.
- Cap the tube and tilt it to allow the hydrogen peroxide solution to cover the colony
- Look for vigorous bubbling occurring within 10 seconds
- Agar slant method
- • Add 3-4 drops of hydrogen peroxide to an overnight growth on an
agar slant and replace the cap
- • Look for vigorous bubbling occurring within 10 seconds
- Cover-slip method
- • One drop of hydrogen peroxide solution is placed on a slide.
- • A small portion of the suspect colony is spotted onto the centre
of a cover-slip.
- • Invert the cover-slip and place it on the drop of hydrogen peroxide
- • Look for vigorous bubbling occurring within 10 seconds.
Positive result: Vigorous
bubbling indicates the presence of catalyse
Negative result: No