113.4 Monday, Jan. 7 Gut microbes facilitate consumption of toxic diets by herbivores KOHL, K.D.*; WEISS, R.B.; DALE, C.; DEARING, M.D.; Univ of Utah; Univ. of Utah; Univ of Utah; Univ of Utah email@example.com
For decades, ecologists have hypothesized that herbivorous mammals might host beneficial microbes that facilitate the ingestion of diets containing toxic plant secondary compounds (PSCs). However, this idea has never been sufficiently tested in wild herbivores. We studied a small herbivorous rodent, the desert woodrat (Neotoma lepida) that naturally feeds on a toxic shrub, creosote bush (Larrea tridentata). Creosote leaves produce large quantities of a phenolic-rich resin that is lethal to lab mice in the doses consumed by woodrats. Woodrats were fed either a control diet of rabbit chow or rabbit chow plus 2% extracted creosote resin. Animals were dissected and we conducted metagenomic sequencing of the contents of the woodrat foregut. Additionally, a subset of animals were given a broad-spectrum antibiotic (neomycin); food intake and body mass were monitored. When feeding on creosote resin, the woodrat foregut metagenome was notably enriched in genes associated with the metabolism of aromatic compounds, stress responses, protein metabolism, carbohydrate metabolism, and membrane transport. Woodrats given antibiotics consumed less food and lost more weight compared to woodrats not given antibiotics, but only when the diet contained PSCs. Metagenomic results revealed that dietary toxins strongly alter the functional profile of woodrat gut microbes, which may have impacts on host homeostasis. The antibiotic study represents the first experimental evidence that microbes enhance the consumption of PSCs in wild herbivores. These results suggest that beneficial microbes play a large role in enhancing dietary niche breadth in herbivores by allowing them to consume toxic plants. This may have implications for wild and domesticated herbivores facing rapid changes in plant communities due to changes in global climate or land-use practices.