Glycerol utilization during nutrient stress in the Lyme disease bacterium

The bacterium Borrelia burgdorferi causes Lyme disease, the most common tick-borne illness in the Northern hemisphere. The bacterium lives in an enzootic cycle, transiting between a tick vector and a vertebrate host. While in the tick, B. burgdorferi uses glucose from the blood meal as a carbon source for glycolysis, a catabolic pathway that produces energy. When the blood meal is digested and absorbed by the tick midgut, the bacterium must find a different source of carbon to survive. Glycerol, a three-carbon sugar alcohol used as an anti-freeze in the tick, can serve as a substitute carbon source for glycolysis during this period of nutrient stress. A set of genes called the glp operon encode the molecular machinery to utilize glycerol. The last gene in the operon, glpD, encodes glycerol-3-phosphate dehydrogenase, which is the gateway that shuttles glycerol to either glycolysis (as an energy source) or membrane biosynthesis. The GlpD enzyme appears to have two domains: an FADH2-binding domain and a small “cap” domain. Preliminary data suggest that the cap domain may be made as an independent protein. The cap domain was overexpressed and purified to determine its functional role in B. burgdorferi. Further analyses will be done to determine structure and enzymatic activity