The gut microbiota regulates many aspects of human physiology, but the molecular mechanisms by which specific microbes influence health and disease are not fully understood. Germ-free (GF) and gnotobiotic mouse models are crucial for elucidating these complex interactions. The Host-Microbiota-Interaction (HMI) lab, led by Prof. Lars Vereecke, utilizes these models to uncover mechanisms underlying inflammatory diseases and cancer. The HMI lab develops transgenic mouse models of intestinal inflammation and colorectal cancer, rederiving these lines under germ-free conditions to investigate microbiota-driven disease mechanisms. By using patient-derived bacterial and fungal strains, we conduct infection experiments at multiple levels of microbial complexity, identifying microbially driven disease mechanisms. Additionally, we study microbes that enhance response to immunotherapy, paving the way for novel microbiota-based therapies.