Figure 4.

Ultracentrifuge tubes with rickettsiae purified from Vero 76 cells by Renografin density gradient ultracentrifugation. The rickettsiae were purified from six 150cm² flasks of heavily infected cells. (A) Tubes after the first run through the Renografin gradient. The black arrow points to the band of viable rickettsiae at the 32%–36% Renografin interface. The red arrowhead points to the debris at the SPG-32% Renografin interface. (b) Tubes after the second run through the Renografin gradient. The black arrow points to the band of viable rickettsiae at the 32%–36% Renografin interface.