PRJNA546505
B. burgdorferi RpoS regulon
Differential gene expression in B. burgdorferi, the Lyme disease spirochete, is coordinated in part by a complex regulatory pathway that involves the alternative ? factors RpoN and RpoS and two ancillary trans-acting factors, BosR and Rrp2. This pathway is activated during the nymphal blood meal when RpoS, the primary effector, upregulates transcription of genes required for tick-to-mammal transmission and early infection in mammals. RpoS also exerts a 'gatekeeper' function in mammals by repressing a subset of sigma70-dependent genes that function primarily or exclusively within the vector. Comparative transcriptomics revealed considerable divergence between the strain B31 and 297 RpoS regulons under mammalian host conditions, including members of multiple paralogous gene families encoding differentially-expressed, sequence variable outer surface lipoproteins. Thus, while RpoS and its gatekeeper function are stringently regulated to ensure transit of spirochetes between vector and mammals, as well as persistence once infection has been established, diversity within the RpoS regulon could be an important determinant of the range of hosts capable of serving as competent reservoirs for individual borrelial strains and their degree of virulence for humans.