The anaerobic gut microbe Akkermansia muciniphila ATCC BAA-835 lives in the mucus layer where it is exposed to oxygen. To investigate how it survives the changing oxygen concentrations, we exposed a exponentially growing culture to oxygen. The experiment was performed in parallel fermentor systems. To one system we added 0.2l/h oxygen after the culture reached an OD of 0.1, while the other remained anaerobic. Samples were taken just before addition of oxygen, about 1h after and when the cell reached stationary phase.