Regulation of Psuc, a sucrose-inducible promoter in Caulobacter crescentus

In gram-negative bacteria, when nutrients are too large or too scarce to diffuse through outer membrane porins, TonB-dependent receptors (TBDRs) are utilized to actively translocate substrates across the outer membrane. <i>Caulobacter crescentus</i> is a gram-negative bacterium with a large set of TBDRs, many which have not been fully characterized. Previous studies identified SucA, a <i>Caulobacter</i> TBDR that transports sucrose. Our experiments further characterize the expression of <i>sucA</i> from the <i>P _suc</i> promoter and we identify <i>P _suc</i> as a tightly controlled, tunable promoter, responsive to changes in sucrose concentration with and without other carbon sources in the media.