CELL-DENSITY-DEPENDENT EXPRESSION OF BORRELIA-BURGDORFERI LIPOPROTEINS IN-VITRO

Previously, we had identified non-OspA-OspB surface proteins of Borrel ia burgdorferi that are targeted by the antibody-dependent complement- mediated killing mechanism, Here we demonstrate by Western blotting th at one of these proteins, P35, is upregulated at the onset of stationa ry phase in vitro, Northern analysis revealed that the upregulation of P35 is at the level of transcription, In addition, the expression of an open reading frame (ORF) located downstream of the p35 gene was fou nd to be regulated in the same fashion as that of P35. This ORF encode s a 7.5-kDa lipoprotein, The transcriptional start sites for both of t hese genes were determined, to aid in the identification of the putati ve promoter regions. Additional sequencing of the 5' banking region of the p35 gene revealed a region of dyad symmetry 52 bp upstream of the transcription start site, Southern analysis demonstrated that the exp ression of these genes was not due to a cell-density-dependent rearran gement in the genome of B. burgdorferi. These findings provide an in v itro model for studying mechanisms of gene regulation in B. burgdorfer i.