Arctic ground squirrels (Urocitellus parryii), are the most extreme mammalian hibernators in the world, dropping core body temperature below 0°C for weeks at a time when hibernating during extreme cold exposure. During this period, the gut microbiome and the animal plasma and tissues do not freeze or become damaged. The goal of this research is to determine the difference in gut microbial communities among summer active, thermoneutral hibernating, and cold-stressed hibernating arctic ground squirrels. We hypothesized that the composition of microbial communities would be different as squirrels hibernate across modified ambient temperature conditions, and that there could be microbial cold-resistance genes within both hibernating groups. Metagenomic data was collected from squirrels kept in three conditions: non-hibernating (summer active), hibernating with an ambient temperature of 2°C (thermoneutral), and hibernating with an ambient temperature of -16°C (cold-stressed). The microbial taxa within the metagenomic reads were classified using Kaiju - v1.9.0. Additionally, the data is actively being analyzed for gene expression of microbial cold-resistance mechanisms. The preliminary results for microbial taxa showed variation between the three temperature groups. The dominant phyla within all temperature groups were Bacillota (Summer: 62.6%, 2°C: 32.3%, -16°C: 40.1%) and Bacteroidota (Summer: 29.7%, 2°C: 42.4%, -16°C: 44.1%), but their relative abundances differed across the three groups. Followup statistical analysis will determine the significance of the differences between the relative abundances. Other notable differences included the relative abundance of the phylum Verrucomicrobiota (Summer: 1% relative abundance. Results showed the composition of the microbial communities was different between the three groups, but each exhibited unique bacterial features. When plotted, the cold-stressed group microbiota visually appears to fall in between the summer and thermoneutral hibernation conditions, which could have resulted from increased arousals from cold body temperatures due to cold stress (finalized statistical analysis is pending). Currently, metagenomic methods (gene assembly and annotation) are also being used to locate the presence of cold-resistance genes within the three temperature groups. Research reported in this publication was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103395. The content is solely the responsibility of the authors and does not necessarily reflect the official views of the NIH. This material is based in part upon work supported by NASA through the Alaska Space Grant Program (80NSSC20M0070). This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Chakraborty et al. (Fri,) studied this question.