Search

YapC, a putative Yersinia pestis autotransporter protein, shows strong homology to the enterotoxigenic Escherichia coil adhesin TibA. As a potentially important surface protein of Y. pestis, we analysed YapC for several activities. When expressed in the non-pathogenic [Fim.sup.-] E. coil strain AAEC185, YapC mediated attachment to both murine-derived macrophage-like cells (RAW264.7) and human-derived epithelial-like cells (HEp-2). In addition, expression of YapC on the surface of E. coil led to autoaggregation in DMEM tissue culture medium, a phenomenon associated with virulence in Yersinia species. YapC also mediated formation of biofilm-like deposits by E. coil AAEC185. Deletion of yapC in Y. pestis strain KIM5 resulted in no change in adhesion to either RAW264.7 or HEp-2 cells, or in biofilm formation. Lack of a phenotype for the Y. pestis AyapC mutant may reflect the relatively low level of yapC expression in vitro, as assessed by RT-PCR, and/or redundant functions expressed in vitro. These data demonstrate several activities for YapC that may function during Y. pestis infection.

RovA is a MarR/SlyA-type regulator that mediates the transcription of inv in Yersinia enterocolitica and Y. pseudotuberculosis. In Y. pseudotuberculosis, rovA transcription is controlled primarily by H-NS and RovA, which bind to similar regions within the rovA promoter. At 37[degrees]C, rovA transcription is repressed by H-NS. Transcription of rovA results when RovA relieves H-NS-mediated repression. The region of the rovA promoter that H-NS and RovA bind is not conserved in the Y. enterocolitica promoter. Using green fluorescent protein reporters, we determined that the Y. enterocolitica rovA ([rovA.sub.Yent]) promoter is weaker than the Y. pseudotuberculosis promoter. However, despite the missing H-NS/RovA binding site in the [rovA.sub.Yent] promoter, H-NS and RovA are still involved in the regulation of [rovA.sub.Yent] DNA binding studies suggest that H-NS and RovA bind with a higher affinity to the Y. pseudotuberculosis/Y. pestis rovA ([rovA.sub.Ypstb/Ypestis]) promoter than to the [rovA.sub.Yent] promoter. Furthermore, H-NS appears to bind to two regions in a cooperative fashion within the [rovA.sub.Yent] promoter that is not observed with the [rovA.sub.Ypstb/Ypestis] promoter. Finally, using a transposon mutagenesis approach, we identified a new positive regulator of rovA in Y. enterocolitica, LeuO. In Escherichia coli, LeuO regulates gene expression via changes in levels of RpoS and H-NS, but LeuO-mediated regulation of [rovA.sub.Yent] appears to be independent of either of these two proteins. Together, these data demonstrate that while the rovA regulatory factors are conserved in Yersinia, divergence of Y. enterocolitica and Y. pseudotuberculosis/Y. pestis during evolution has resulted in modifications in the mechanisms that are responsible for controlling rovA transcription.