A Δ hsdR mutant is unaffected in virulence factor production. E2348/69 and NH4 were grown under conditions that stimulate virulence factor production and BfpA (a) levels were measured by western analysis of whole cell lysates. Secreted Tir (b) levels were measured by western analysis of SDS-PAGE gels after electrophoresis of precipitated supernatant samples. (c) Levels of a cross-reactive protein serve as a loading control. The experiment was performed twice and one experiment is shown.