Here's why:

* Catalase is an enzyme that breaks down hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂).

* Streptomyces produce catalase as part of their normal metabolic processes. This enzyme helps them protect themselves from the toxic effects of reactive oxygen species (ROS) like hydrogen peroxide.

Therefore, when you perform a catalase test on Streptomyces, you will typically observe the production of bubbles, indicating the breakdown of hydrogen peroxide.

Important Note: There are exceptions to this general rule. Some species of Streptomyces might exhibit weak or no catalase activity.