- Test for the enzyme catalase on your unknown isolates
Hydrogen peroxide \(H_2O_2\) is a by-product of respiration and is lethal if it accumulates in the cell. The enzyme catalase degrades the hydrogen peroxide in the cell before it can do any cell damage. It splits the H2O2 to free oxygen (bubbles) and water. Generally, the test reaction is very fast and obvious bubbles will be seen. Catalase is made by your own cells, as well as a variety of other cells, including many bacteria. This test is particularly important for the gram + bacteria. For example, the genus Staphylococcus is a + catalase reaction, whereas the genus Streptococcus is a – catalase reaction.
- Read the slide reaction against a DARK background, preferably black: otherwise it is difficult to see the bubbles.
- Use a culture growing on AN AGAR PLATE OR AGAR SLANT to run the slide catalase test.
- You can drop H2O2 directly on an agar plate or slant, but it may kill the culture.
- 3% hydrogen peroxide
- Pick the inoculum from a plate culture or slant culture and place it on a slide.
- Add one drop of H2O2 and look for immediate bubbling.
Usually immediately you will see a reaction if there is one, most often lots of bubbles. Slight bubbles indicate a positive reaction also.
- What are the bubbles that you see in a + reaction?
- Name the reagent used for this test.
Jackie Reynolds, Professor of Biology (Richland College)