Faculty Mentor: Jack Jurmu (School of Biological Sciences, University of Utah)

Herbivorous mammals that consume toxic plants provide valuable insights into host physiology-microbiome interaction. The Desert woodrat (Neotoma lepida) has developed the capacity to consume the creosote bush (Larrea tridentata) with a high concentration of the toxic compound nordihydroguaiaretic acid (NDGA)(Arteaga et al., 2005). While earlier research has suggested that the gut microbiome plays a role in detoxification mechanisms, the particular microbial taxa involved are unclear (Kohl et al., 2014). In the present study, we cultured nearly 200 microbes from the gastrointestinal tracts of creosote-feeding woodrats. Using growth curve assays, we compared microbial resistance and tolerance to NDGA and identified numerous strains that grew or survived well in its presence. Of particular interest were Klebsiella pneumoniae and a novel isolate, JJ9F70, which grew well in NDGA-containing media, implying detoxification involvement. In contrast, Enterococcus faecalis was inhibited completely, validating NDGA’s selective toxicity. The results indicate that certain gut microbes allow woodrats to digest toxic food sources, thereby conferring ecological benefit along with insight into the evolution of symbiotic detoxification processes. Current work is aimed at elucidating the genetic basis of NDGA metabolism. Because many plant secondary metabolites are structurally similar to pharmaceuticals, the research may also yield greater insight into differences in drug metabolism among individuals in humans, thereby highlighting the significant biomedical relevance of research on non-model organisms.

Bibliography

Acamovic, T., & Brooker, J. D. (2005). Biochemistry of plant secondary metabolites and their effects in animals. The Proceedings of the Nutrition Society, 64(3), 403–412.

Arteaga, S., Andrade-Cetto, A., & Cárdenas, R. (2005). Larrea tridentata (Creosote bush), an abundant plant of Mexican and US-American deserts and its metabolite nordihydroguaiaretic acid. Journal of Ethnopharmacology, 98(3), 231–239.

Dearing, M. D. et al. (2022). Toxin tolerance across landscapes: Ecological exposure not a prerequisite. Functional Ecology.

Freeland, W. J., & Janzen, D. H. (n.d.). Strategies in Herbivory by Mammals: The Role of Plant Secondary Compounds. Source: The American Naturalist, 108(961), 269–289.

Kohl, K. D., Weiss, R. B., Cox, J., Dale, C., & Dearing, M. D. (2014). Gut microbes of mammalian herbivores facilitate intake of plant toxins. Ecology Letters, 17(10),

Magnanou E, Malenke JR, D. M. (2009). Expression of biotransformation genes in woodrat (Neotoma) herbivores on novel and ancestral diets: identification of candidate genes responsible for dietary shifts. Molecular Ecology, 18, 2401–2414.

Mangione, A. M., Dearing, D., & Karasov, W. (2001). Detoxification in relation to toxin Tolerance in Desert Woodrats Eating Creosote Bush. Journal of Chemical Ecology, 27(12).

Mangione, A. M., Dearing, M. D., & Karasov, W. H. (2000). Interpopulation Differences in Tolerance to Creosote Bush Resin in Desert Woodrats (Neotoma lepida). Ecology, 81(8), 2067.