Some of the most important interactions that facilitate mammalian life are between mammals and the diverse communities of microbes that reside within their digestive tracts. Mammalian herbivores in particular exhibit the most diverse gut microbial communities, which are thought to conduct fiber fermentation and other nutritional processes to benefit the host. However, in addition to fiber, plants also produce plant secondary compounds that act as anti-herbivore defenses. It has long been proposed that mammalian herbivores might also house microbes that detoxify these toxic compounds. This proposal aims to advance our knowledge of the microbes that live within the guts of a group of herbivorous rodents: woodrats. Woodrats hold tremendous promise for understanding diversity and for discovery of novel detoxifying microbes and genes, as they feed on a variety of plants containing toxins that likely have shaped gut microbial diversity. Indeed, microbes do allow woodrats to consume plant toxins, and the consumption of these toxins strongly changes their gut microbial communities. The central objective of the proposed research is to understand the biodiversity and community ecology of the gut microbiota in herbivores with respect to dietary toxins. The research will specifically investigate how evolutionary history and exposure to dietary toxins influence the community genetics of foregut microbes in a wild herbivore, and how dietary toxins might alter resident gut microbial communities and allow for invasion by a novel community.
This project will support the training of a graduate student in the emerging field of microbial metagenomics. In addition, high school and undergraduate students will be involved in the research and receive mentoring in the conduct of independent research. This project will support the development of an inquiry-based lecture geared towards the public, which will be presented at local schools and museums. Results from this research will identify important microbial genes associated with the detoxification of plant toxins, which could be useful in agricultural systems, especially in developing areas where livestock often need to feed on plants containing such toxins.
This project focused on the community ecology of microbes living within the guts of herbivores. At every meal, many wild and agricultural herbivores are faced with eating toxic plants. Gut microbes have been proposed to degrade plant toxins for the benefit of herbivores, allowing them to eat otherwise poisonous plants. However, this idea has not been thoroughly tested. Our studies focused on woodrats, small herbivorous rodents that tend to specialize on toxic plants. We conducted a number of experiments to show that gut microbes allow woodrats to consume a toxic shrub, creosote bush. First, we inventoried the collection of microbial genes in the guts of woodrats feeding on a toxin-free diet and those feeding on a diet containing creosote toxins. We found that woodrats feeding on creosote toxins harbored a community enriched in genes associated with detoxification. Second, we used antibiotics to reduce microbial density in the woodrat gut and found that these animals were unable to feed on creosote toxins. Last, we transferred the microbial community from toxin-adapted woodrats to a naïve population and effectively increased the ability of these recipients to feed on toxins. Together, our work presents the most thorough study demonstrating that gut microbes allow wild herbivores to feed on toxic plants. Our project has implications for the possibility of transferring gut microbes from wild herbivores into agricultural herbivores to increase their tolerance of plant toxins. This project also resulted in a number of broader impacts. Two undergraduate research students were mentored to complete independent research projects, with both serving as co-authors on peer reviewed publications. Further, the Co-PI conducted two lectures for the public at the Natural History Museum of Utah to expose members of the general public to scientific research.
