UC Davis

Thiamin pyrophosphate (ThDP), the active form of thiamin (vitamin B₁), is believed to be an essential cofactor for all living organisms^1,2. Here, we report the unprecedented result that thiamin is dispensable for the growth of the Lyme disease pathogen Borrelia burgdorferi (Bb)³. Bb lacks genes for thiamin biosynthesis and transport as well as known ThDP-dependent enzymes⁴, and we were unable to detect thiamin or its derivatives in Bb cells. We showed that eliminating thiamin in vitro and in vivo using BcmE, an enzyme that degrades thiamin, has no impact on Bb growth and survival during its enzootic infectious cycle. Finally, high-performance liquid chromatography analysis reveals that the level of thiamin and its derivatives in Ixodes scapularis ticks, the enzootic vector of Bb, is extremely low. These results suggest that by dispensing with use of thiamin, Borrelia, and perhaps other tick-transmitted bacterial pathogens, are uniquely adapted to survive in tick vectors before transmitting to mammalian hosts. To our knowledge, such a mechanism has not been reported previously in any living organisms.