FIG. 2.

bba74 is transcribed by σ⁷⁰ but requires both mammalian host signals and RpoS for downregulation in vivo. (A) The transcriptional start site for bba74 identified by primer extension analysis is indicated by an arrow. Putative −10 and −35 σ⁷⁰ factor recognition motifs (boxed) as well as a poly(T) tract (underlined) are indicated below. RBS, ribosomal binding site. (B) RpoS-deficient spirochetes fail to downregulate BBA74 during cultivation within DMCs. Whole-cell lysates prepared from wild-type (WT) and rpoS mutant (ΔrpoS) strain 297 isolates were separated by SDS-PAGE and then silver stained to assess expression of OspA and OspC or immunoblotted using specific antisera directed against OspE and BBA74. Reactivity against FlaB was used to confirm that equivalent amounts of lysate were loaded per lane. α, anti.