Adaptation of Akkermansia muciniphila to the Oxic-Anoxic Interface of the Mucus Layer.

colonizes the mucus layer of the gastrointestinal tract, where the organism can be exposed to the oxygen that diffuses from epithelial cells. To understand how is able to survive and grow at this oxic-anoxic interface, its oxygen tolerance and response and reduction capacities were studied. was found to be oxygen tolerant. On top of this, under aerated conditions, showed significant oxygen reduction capacities and its growth rate and yield were increased compared to those seen under strict anaerobic conditions. Transcriptome analysis revealed an initial oxygen stress response upon exposure to oxygen. Thereafter, genes related to respiration were expressed, including those coding for the cytochrome complex, which can function as a terminal oxidase. The functionality of cytochrome genes was proven by successfully complementing cytochrome-deficient strain ECOM4. We conclude that can use oxygen when it is present at nanomolar concentrations. This article explains how , previously described as a strictly anaerobic bacterium, is able to tolerate and even benefit from low levels of oxygen. Interestingly, we measured growth enhancement of and changes in metabolism as a result of the oxygen exposure. In this article, we discuss similarities and differences of this oxygen-responsive mechanism with respect to those of other intestinal anaerobic isolates. Taken together, we think that these are valuable data that indicate how anaerobic intestinal colonizing bacteria can exploit low levels of oxygen present in the mucus layer and that our results have direct relevance for applicability, as addition of low oxygen concentrations could benefit the growth of certain anaerobic organisms.