Final answer:
The reagent used in a bacterial catalase test is 3% hydrogen peroxide, and it is used to determine if bacteria can produce the enzyme catalase, indicating an aerobic lifestyle.
Step-by-step explanation:
The reagent that is used to perform a bacterial catalase test is 3% hydrogen peroxide. During the test, a small sample of a bacterial culture is mixed with a drop of hydrogen peroxide on a slide. If the bacteria are capable of producing catalase, an enzyme that breaks down hydrogen peroxide into water and oxygen, you will observe bubbling as oxygen is released. This bubbling is an indication of a positive catalase test and suggests that the bacteria live aerobically and can perform aerobic respiration to produce ATP. This test is a simple and rapid method to differentiate between aerobic and anaerobic bacteria, such as distinguishing streptococci (aerotolerant anaerobes without catalase) from staphylococci (facultative anaerobes with catalase).