Catalase Test

Objective:

            To determine the ability of bacteria that produces Catalase enzyme which degrades the hydrogen peroxide.

 Principle:

           

            The enzyme Catalase produced by several bacteria, which is breakdown the hydrogen peroxide and releases oxygen and water. Organisms are producing O₂ products like superoxide and hydrogen peroxide during cell respiration, accumulation of hydrogen peroxide and superoxide leads to the destruction of cell constituents and death of the organisms. The superoxide dismutase enzyme, which catalyzes the destruction of toxic superoxide and Catalase enzyme which catalyzes the degradation of hydrogen peroxide. Obligate aerobes and certain anaerobes contain these types of enzymes, but most of the strict anaerobes lack of above enzymes and therefore they cannot tolerate oxygen.

              

Catalase production can be determined by addition of the substrate H₂O₂ on bacterial culture, if bacteria produce catalase enzyme the above said chemical reactions liberate oxygen gas and producing bubbles, it indicates the presence of catalase. This test also useful for differentiate the morphological similar organisms like Enterococcus (Catalse negative) and Staphylococcus (Catalase positive).

           

Materials required:

- 24 Hours old bacterial cultures (Staphylococcus  and Streptococcus )

- 3 % Hydrogen Peroxide (H₂O₂)
- Glass slide/ test tube

- Inoculation loop/ glass rod

Procedure:

1.      Slide Method:
   - Pure growth of the organisms will transfer the clean slide by using inoculation loop or glass rod.
  -   Immediately add a drop of 3% hydrogen peroxide on bacterial culture.
    -  Observe the bubble formation (Effervescence).

2. Tube Test:
-   Take one ml of 3 % hydrogen peroxide in test tube.

-   Small amount of bacterial culture introduce into the solution

-   Immediately observe the effervescence.

Result:

 Staphylococcus  is shows catalase positive with bubble formation

 Streptococcus is catalase negative with no bubble formation

                                                                            a)
                                                    
                                                                  b)

              

Interpretation:

           In aerobic organisms, during aerobic respiration, oxygen serves as hydrogen acceptor and hydrogen peroxide is formed in the cell. High concentration of H₂O₂  is formed which is toxic to cell.  Staphylococcus posses the catalase enzyme that converts hydrogen peroxide into oxygen and water. Streptococcus doesn’t releases catalase enzyme and this organism doesn’t convert

H₂O₂ into oxygen.

Catalase Positive Organisms:

Staphylococcus,           

E.coli,           

Pseudomonas aeroginosa,         

Klebsiella,

Salmonella,         

 Shiegella,

Proteus,

 Enterobacter,

 Citrobacter.

Catalase Negative Organisms:

Streptococcus

Most of the anaerobic organisms