All animals are colonized by a large number of non disease-causing microorganisms, referred to as the normal microbiota. Sites colonized by these microorganisms include the skin and the genital tracts, with the most heavily colonized site being the large intestine. The intestinal microbiota carries out important roles in a variety of areas, such as absorption of nutrients and prevention of infectious disease. Dr. Claudia Lupp is investigating the importance of the intestinal microbiota in diarrheal disease caused by enteropathogenic Escherichia coli (E. coli). Enteropathogenic E. coli include the human pathogens enterohemorrhagic and enteropathogenic E. coli (EHEC and EPEC), which cause significant illness and death around the world. She will use the closely related mouse pathogen Citrobacter rodentium as an experimental model to determine the effects of diarrheal disease on the normal microbiota and to investigate how the microbiota might be manipulated in order to prevent disease. Understanding the body’s innate defenses against infectious disease, including those provided by the normal microbiota, is important for health maintenance. This information ultimately may be used for strategies to prevent and to cure infectious disease by bolstering the body’s natural defenses.