In many animals, bacteria vastly outnumber of animal cells. Most of the associations between animals and bacteria are benign and some are beneficial, but under some circumstances, commensal (benign) bacteria convert to pathogens, resulting in diseases such as endocarditis and sepsis. This switch is poorly understood, but may involve changes in host physiology or immune status or bacterial entry into organs where they normally do not reside. The animal gut is a common source of bacteria that undergo the commensal-to-pathogen switch, but the complexity of the microbial communities in many animals' guts presents a barrier to studying the gut community's interactions with the host that lead to the change in health status. The investigators will study the commensal-to-pathogen switch of normal gut residents in a common caterpillar, the larva of the gypsy moth. The project aims to understand the fundamental ecological interactions that enable a bacterium that is a normal member of the gypsy moth gut flora to incite disease and death in the presence of a toxin produced by another bacterium. The study will test the hypotheses that the conversion to pathogen is associated with host's inflammatory response and that the normal microbial community of the gut mediates the commensal-to-pathogen switch. The project will provide the context for providing summer research experiences for undergraduate students from historically black universities. They will be recruited from participating universities in cohorts to provide them a peer group during the research program. All mentors of the summer students will be trained in the course, Entering Mentoring, which was developed by the PI, to ensure a successful research experience for every student.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Mary Beth Saffo
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Yale University
New Haven
United States
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