Catalase is an enzyme present in most of the organisms.
The catalase test is to identify species of bacteria.
The presence of catalase enzyme in the test isolate is detected using hydrogen peroxide. If the bacteria possess catalase, when a small amount of bacterial isolate is added to hydrogen peroxide, bubbles of oxygen are observed.
2H2O2 –catalase–> 2H2O + O2
The catalase test is done by placing a drop of hydrogen peroxide on a microscope slide. Using an applicator stick, a scientist touches the colony, and then smears a sample into the hydrogen peroxide drop.
If the mixture produces bubbles, the organism is said to be 'catalase positive’
If not, the organism is ‘catalase negative’
Uses Catalase Test Results
1. The catalase test is primarrily used to distinguish among Gram-positive cocci: members of the genus Staphylococcus are catalase-positive, and members of genera Streptococcus and Enterococcus are catalase-negative.
2. Catalase test is used to differentiate aertolerant strains of Clostridium, which are catalase negative, from Bacillus species, which are positive.
3. Semiquantitative catalase test is used for the identification of Mycobacterium tuberculosis.
4. Catalase test can be used as an aid to the identification of Enterobacteriaceae. Members of Enterobacteriaceae family are catalase positive.
Catalase was not noticed until 1818 when Louis Jacques Thrénard, who discovered H2O2 (hydrogen peroxide), suggested its breakdown is caused by an unknown substance.