All environmentally exposed surfaces of the human body are colonized by a tremendous diversity of microbes (bacterial, viral, protozoal, fungal). Collectively, this community of microbes (a.k.a. the ‘microbiota’) reaches it’s highest density and diversity in the gut. Through their combined metabolic activities and competitive interactions, these symbionts have a fundamental effect on organismal fitness, and consequently evolution, that we are only just beginning to unravel. Research in the Kubinak lab seeks to understand the physiological relevance of interactions between hosts and their resident microbiota, with a particular emphasis on how this relationship governs gastrointestinal health.