Science Buddies: "Ask an Expert"

Hey, I'm trying to differentiate aerobic bacteria from anaerobic bacteria and found a study that used methylene blue using this mechanism (I'm assuming) to differentiate the two. However, I don't understand how that would work as the glycolysis occurs in both the aerobic and anaerobic respiration. Does anybody know how it works?

Hello,

That's a great question!

In aerobic respiration, the electron transport chain (ETC) uses oxygen as the final electron acceptor. However, when oxygen is not present, cells can switch to either fermentation or anaerobic respiration.
Fermentation: This process involves only glycolysis, where the pyruvate that is produced from glucose is also reduced. Since the cell doesn't use the ETC, there is no need for a final electron acceptor.
Anaerobic Respiration: This process involves all three stages of respiration, including the ETC. However, instead of oxygen, other molecules serve as the final electron acceptor.

Methylene blue is a redox indicator, meaning it changes color based on oxidation state. In its oxidized state, it is blue and in its reduced state, it becomes colorless.

In aerobic respiration, oxygen is available as the final electron acceptor, so the methylene blue remains unchanged in its oxidized (blue) state. However, in anaerobic respiration, molecules in the methylene blue act as the final electron acceptor, reducing it and turning it colorless.

I hope that helps!