Final answer:
The methylene blue strip is added to the Brewer-type anaerobic jar to create an anaerobic environment for the growth of bacteria. It acts as an indicator of anaerobic conditions, becoming colorless in the absence of oxygen. This helps remove residual oxygen from the jar and creates a suitable environment for the growth of anaerobic bacteria.
Step-by-step explanation:
The methylene blue strip is added to the Brewer-type anaerobic jar in order to create an anaerobic environment for the growth of bacteria. Methylene blue acts as an indicator of anaerobic conditions because it is blue in the presence of oxygen but becomes colorless in the absence of oxygen. By adding the methylene blue strip, any residual oxygen is removed from the jar and replaced with carbon dioxide, creating a suitable environment for the growth of anaerobic bacteria.