"A study in the July issue of PLoS Pathogens has shown that B. 
burgdorferi metabolizes the tick's antifreeze while living in its 
midgut. Many arthropods and insects produce large amounts of antifreeze 
to protect themselves from freezing temperatures. The Ixodes tick's 
antifreeze is glycerol, the same stuff that's often added to enzymes to 
keep them from freezing in laboratory 
freezers. The amount of glycerol found in other organisms is too low to 
serve as antifreeze. I describe below how B. burgdorferi handles 
glycerol, but the same enzymes are found in most organisms that 
metabolize glycerol, including humans."