PNPT1 and infection: In both Y. pestis and Y. pseudotuberculosis, PNPase was required for optimal virulence in cell culture infections (as measured by bacterial proliferation vis a vis mouse macrophage-like cells and degree of induced HeLa cell rounding, an indirect measure of TTSS function) (Rosenzweig et al., 2005) as well as in murine models of infection (Rosenzweig et al., 2007; Lawal et al., 2011).