To study the organisms that are capable of producing the enzyme catalase.
Most aerobic and facultative bacteria utilize oxygen to produce hydrogen
peroxide. This hydrogen peroxide that they produce is toxic to their own enzyme
system. Thus, hydrogen peroxide acts as an antimetabolite.
Their survival in the presence of toxic antimetabolite is possible because
these organism produce an enzyme called catalase. This enzyme converts
peroxides into water and oxygen.
The enzyme catalase present in most microorganisms is responsible for the
breakdown of toxic hydrogen peroxide that could accumulate in the cell as a
result of various metabolic activities into nontoxic substances, water, and oxygen.
The hydrogen peroxide formed by certain bacteria is converted to water and
oxygen by the enzyme reaction. This best demonstrates whether that organism
produces catalase or not. To do this test, all that is necessary is to place a few
drops of 3% hydrogen peroxide on the organism present as a slant culture. If
the hydrogen peroxide effervesces, the organism is catalase-positive.
Alternatively, a small amount of culture to be tested is picked from NA and
the organism is placed on top of the hydrogen peroxide. The production of gas
bubbles indicates a positive reaction.
- Test tubes with slant bacterial culture
3% hydrogen peroxide.
- Direct tube test: The tube is held at an angle and a few drops of 3%
hydrogen peroxide is allowed to flow slowly over the culture. The emergence
of bubbles from the organism is noted. The presence of bubble indicates a
positive reaction, demonstrating the presence of enzyme catalase. If no gas
is produced, this is a negative reaction.
- Slide technique: With the help of a sterile platinum loop, transfer a small
amount of culture onto a clean slide. About 0.5 mL of 3% hydrogen
peroxide is added to the culture.
If bubbles are formed, it indicates a positive reaction, i.e., the presence of the