Meeting Abstract
Bacteria resident in vertebrate guts expand their hosts’ metabolic capabilities and modulate development, immunology and diverse physiological functions. Hibernation is a unique system to understand the interplay among host biology, diet and microbiota in mammals because extended winter fasting eliminates a major source of substrates for bacterial metabolism, with potential effects on symbiotic interactions. The annual hibernation cycle reconfigures microbiota composition in 13-lined ground squirrels, increasing relative abundance of taxa that can degrade host-derived substrates and reducing abundance of taxa that prefer plant glycans. The intestinal immune system, the host’s primary sensor of gut microbiota, is also remodeled during winter fasting. We use stable isotope-assisted breath analysis and antibiotic manipulation to examine how seasonal changes in microbiota composition influence function in vivo, and affect host characteristics that are associated with microbial activity. Active season squirrels and aroused hibernators were gavaged with 13C-labeled substrates including inulin, a complex plant-derived fiber, and mannitol, a simple sugar alcohol, neither of which are metabolized by mammalian enzymes; the ratio of 13CO2 /12CO2 in breath reflects bacterial substrate degradation in vivo. Hibernation progressively reduces bacterial capacity to degrade 13C-inulin, whereas breath responses to 13C-mannitol are unaffected. Antibiotic manipulations alter host immune and epithelial features and increase visceral fat in summer squirrels. These studies confirm strong effects of hibernation on microbiota function in vivo and suggest a potential role for gut symbionts in hibernation physiology.
