The human gut is home to trillions of microorganisms, which have a great impact on our health. One of the key players in this community is a bacterium called Akkermansia muciniphila. The levels of A. muciniphila are shown to be decreased in many illnesses and these bacteria play a major part in controlling obesity and metabolic disorders, such as type 2 diabetes. In this thesis, the metabolism of A. muciniphila was studied in detail to understand its physiological role in the gut of humans. In addition, host interaction was investigated and specific proteins on the outer membrane of the bacteria were recognized as central factors in modulating the host immune response. Identifying the molecular mechanisms of host-microbe interactions is essential for understanding their role in human health. Therefore, the findings of this thesis are an important contribution to the study of A. muciniphila, which is a promising candidate for a next-generation probiotic or a therapeutic microbe.