Mechanism of repression of the glycerol utilization operon inBorrelia burgdorferi

Lyme disease pathogenBorrelia burgdorferi, switches carbohydrate utilization while transmitting between two disparate hosts, anIxodestick vector and a mammalian host. The ability to use glycerol is important forB. burgdorferito colonize and persist in the tick vector, and expression of theglpFKD(glp) operon for glycerol uptake/utilization is tightly regulated during the enzootic cycle ofB. burgdorferibetween ticks and mammals. In present study, we identified aciselement within the 5’ untranslated region ofglpthat negatively regulates theglpexpression. This repression ofglpis independent of RpoS. We further show that BadR directly binds to thisciselement and repressesglp. The efficiency of BadR binding in the presence of c-di-GMP and various carbohydrates were also assessed. This finding, along with previous findings of positive regulation ofglpexpression by the c-di-GMP signaling pathway and negative regulation by the alternative sigma factor RpoS, demonstrates thatB. burgdorferiemploys multi-layer regulatory mechanisms to coordinateglpexpression during its enzootic cycle.