Erratum
Volume 2, no. 6, doi:10.1128/mBio.00238-11, 2011. The fourth author's name was spelled incorrectly. The byline should appear as shown above.
Volume 2, no. 6, doi:10.1128/mBio.00238-11, 2011. The fourth author's name was spelled incorrectly. The byline should appear as shown above.