The inhabitants of Earth are mostly microbes, and their activities are central to human welfare. Microbes can cause disease, but a properly functioning microbiome is essential for health. Microbes spoil food, but drive many forms of food production. Microbes mediate organismic decay, but catalyze numerous geochemical processes essential for life on Earth.

Research in the Penn Microbiology Department focuses on infectious agents that threaten global health, with an emphasis on understanding molecular mechanisms and developing key new methods. Areas of focus include pathogenic bacteria of the airway and gut, HIV/AIDS, insect- and rodent-borne viruses, herpes viruses, papillomaviruses, emerging infectious diseases and the human microbiome. On the host side, faculty study many areas of immunology related to infection, including innate and adaptive immunity, tumor immunology and vaccine development.