Figure 9. CovR levels are decreased in the CovR-T65A strain.

(A) Western blot analysis. Indicated strains were grown to mid-exponential phase in regular THY medium (−) and in THY medium supplemented with 15 mM MgCl₂ (+). Cell lysates containing 70 µg of total protein were loaded on a 12% SDS-gel. The gel was divided into two parts; the upper part was blotted against anti-CovR antibody while the lower part was blotted against anti-HPr antibody which served as a loading control. (B) qRT-PCR analysis of covR transcript levels. For “Low MgCl₂” and “High MgCl₂” samples, the indicated strains were grown as for the Western blot analysis in duplicate on two separate occasions and analyzed in duplicate. Data shown are mean ± standard deviation of 8 data points. For the “During infection” samples, four animals were infected with each strain and data were analyzed in triplicate as described in Figure 8. Data graphed are mean ± standard deviation of 12 data points. For all three conditions the lack of a bar for 10870ΔcovR strain indicates no covR transcript level was detectable. * designates a significant difference in covR transcript level between strain MGAS10870 and CovR-T65A as determined by Student's t-test.