* Catalase-positive bacteria: These bacteria produce the enzyme catalase, which breaks down hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂). This reaction causes the formation of bubbles when a drop of hydrogen peroxide is added to a bacterial colony. Examples include:
* Staphylococcus
* Micrococcus
* Bacillus
* Catalase-negative bacteria: These bacteria lack the enzyme catalase and therefore cannot break down hydrogen peroxide. No bubbles will be observed when hydrogen peroxide is added to a colony of these bacteria. Examples include:
* Streptococcus
* Enterococcus
Therefore, the catalase test is a simple and rapid way to distinguish between these two groups of bacteria.
