Here's why:
* Methylene blue is a redox indicator. This means it changes color depending on the presence or absence of oxygen.
* In an anaerobic environment, the indicator strip is colorless because it is in its reduced state.
* When oxygen is present, the indicator strip becomes blue as it is oxidized.
This is a problem because GasPak jars are specifically designed to create an anaerobic environment. This is crucial for the growth of anaerobic bacteria, which cannot survive in the presence of oxygen.
Therefore, a blue methylene blue indicator strip indicates that the jar's anaerobic environment has been compromised. This could be due to:
* Faulty GasPak pouch: The pouch may not be generating the correct gas mixture.
* Leaking jar: The jar may have a crack or a loose lid, allowing oxygen to enter.
* Too long incubation: Over time, the gas generated by the GasPak pouch may be depleted, leading to an increase in oxygen levels.
If the indicator strip turns blue, you should:
* Discard the jar and its contents.
* Check the GasPak pouch for damage or expiration date.
* Inspect the jar for any leaks.
* Use a new GasPak pouch and a new jar for your next experiment.
It's important to ensure a proper anaerobic environment for successful anaerobic cultures.
