Erratum
Volume 3, no. 4, doi:10.1128/mBio.00184-12, 2012. Panels D and E in Fig. 1 were omitted from the image. Figure 1 should appear as shown below.
Volume 3, no. 4, doi:10.1128/mBio.00184-12, 2012. Panels D and E in Fig. 1 were omitted from the image. Figure 1 should appear as shown below.