Final answer:
The oxidase test is performed on a culture before using an Enterotube II to identify the culture because it helps differentiate between bacteria that produce cytochrome oxidase or indophenol oxidases and those that do not. By performing the oxidase test, it becomes possible to identify aerobic bacteria with a cytochrome-based electron transport system.
Step-by-step explanation:
An oxidase test is performed on a culture before using an Enterotube II to identify the culture because it helps differentiate between bacteria that produce cytochrome oxidase or indophenol oxidases and those that do not. The oxidase test detects the presence of these redox enzymes in the electron transport system of bacteria, which are usually only found in aerobic organisms that use oxygen as the final electron acceptor in respiration. By performing the oxidase test, it becomes possible to identify aerobic bacteria with a cytochrome-based electron transport system.