Meeting Abstract
Hibernation is a physiological adaptation to reduced food availability characterized by profound fluctuations in diet and physiology. The arctic ground squirrel is the northern most hibernator and exhibits the most extreme hibernation physiology. They reproduce and grow over a 3-4 month active season, increasing fat mass from ~ 5% to over 45% during the last 3 weeks in preparation for hibernation. Hibernation lasts up to nine months, during which they neither eat nor drink, and bouts of torpor (periods of decreased body temperature (Tb), metabolic rate and activity) last up to 25 days, interspersed with periodic arousals to euthermy. During torpor Tb is regulated at -2.9C, the lowest of any mammal. We have demonstrated that seasonal changes in host physiology affect the cecal microbial community of arctic ground squirrels, and that hibernation selects for a core cecal microbiota. Microbial diversity in juvenile squirrels is strongly influenced by genetic or maternal influences and does not shift significantly during pre-hibernation fattening; however, relative abundances of major taxa reflect the obese microbiota observed in other species. We have also found that gut microbial community structure in adult arctic ground squirrels is robust to changes in dietary fat content across the active season, but is responsive at the level of gene expression, perhaps suggesting strong host selection for a fattening microbiota regardless of diet. Finally, in an effort to uncover important functional relationships between arctic ground squirrels and their gut microbiota, we are isolating and characterizing beneficial ureolytic bacteria from the gut, and examining host reliance upon urea nitrogen salvage to conserve protein during the hibernation and active seasons.
