Understanding how animals physiologically respond to changes in their environment is a large challenge in biology. Scientists have discovered that animals host diverse communities of microbes (microbiomes) that help their hosts in many ways, such as digesting fiber or training the immune system. This project focuses on how animals respond to changes in diet and the role of the animals' microbiomes in these responses. For example, animals can change many aspects of their digestive system (intestinal length, activities of digestive enzymes, etc.) in response to changes in nutritional composition. However, not all species respond the same way: herbivorous, omnivorous, and insectivorous rodents respond differently to varying levels of dietary protein and fiber. To ascertain if these differences are due to the animals’ physiology or their gut microbiome, microbiomes of rodent hosts with different feeding strategies will be inoculated into germ-free mice and then these animals will be given contrasting diets. This research will determine whether the different microbiomes allow hosts to respond differently to changes in diet. Understanding these dynamics could be important for species conservation, agricultural practices, etc. Additionally, this grant will fund an undergraduate research experience where students design independent research projects on microbial isolates. This program will allow for students to generate hypotheses, design experiments, and analyze their own results.

Phenotypic flexibility, or the ability of organisms to modulate phenotype in response to environmental changes, allows animals to maintain performance in face of environmental variation. The hologenomic theory of evolution states that natural selection acts on the collection of host and microbial genomes as a unit. One poorly understood aspect of the hologenomic theory of evolution is how much of phenotypic flexibility is facilitated by the host versus by host-associated microbes. Diet is one environmental variable that yields phenotypic flexibility in animal physiology. For example, animals fed high fiber diets generally lengthen their small intestines and enlarge portions of their hindgut. However, not all animal species respond the same to changes in diet composition. Is the source of this variation in responsiveness driven by the animal genome or by host-associated microbes? This question will be tested by inoculating germ-free mice with microbial communities from different wild rodents. Inoculated mice will then be fed diets varying in protein and fiber content to test whether distinct microbial communities yield differences in phenotypic flexibility. Moreover, students in a Course-based Undergraduate Research Experience (CURE) will culture specific microbial species with varying functional capabilities. Students will then design independent research projects to test original hypotheses. Furthermore, these isolates will be powerful for follow-up studies to identify particular microbial taxa that drive aspects of host phenotypic flexibility.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Mamta Rawat
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University of Pittsburgh
United States
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