FIG 2.

The transcriptional regulators VirR and VirS and the virulence-associated protein VapA are the only plasmid-encoded proteins required for growth in macrophages. Murine J774.1 macrophage monolayers were infected with R. equi 103S or 103S^P−, or with R. equi 103S^P− expressing vapA along with an individual regulator (103S^P−/pVirR::hsp60vapA or 103S^P−/pVirS::hsp60vapA) or with both regulators (103S^P−/pVirRSvapA). Intracellular bacterial growth was followed for 48 h postinfection. Values are means ± standard deviations for monolayers, each assessed in triplicate.