What type of bacteria can be identified using the catalase test?

The catalase test is specifically designed to identify bacteria based on their ability to produce the enzyme catalase. This enzyme catalyzes the breakdown of hydrogen peroxide into water and oxygen, which is a vital reaction for aerobic organisms. When hydrogen peroxide is applied to a culture of bacteria that possess catalase, the reaction produces bubbles of oxygen gas, indicating a positive result for the test.

Primarily, aerobic bacteria and some facultative anaerobes can produce catalase, allowing them to survive in environments where hydrogen peroxide is present as a toxic byproduct of cellular respiration. This distinguishes these microorganisms from obligate anaerobes, which do not produce catalase and cannot tolerate oxygen-rich environments.

The other options either falsely limit the scope of the test (for example, suggesting it can only identify Gram-negative bacteria or pathogenic bacteria), or imply a requirement of oxygen for survival, which is not accurate for all bacteria that can be tested. Hence, focusing on the ability to produce the enzyme catalase provides a clear and correct rationale for this identification method.