FIG 1.

Invasion of tick cells occurs through a process dependent on live Rickettsia. Live (L-Rm) or formalin-fixed (FF-Rm) R. montanensis was used to infect DVE1 cells preincubated in medium supplemented with 1% DMSO. After 1 h, Rickettsia was removed, and the cells were washed twice with PBS. The samples were collected by low-speed centrifugation, and gDNA was extracted. Mean (± standard error of the mean) percentages of relative invasion, calculated as the ratio of rickettsial OmpB and tick calreticulin gene copy numbers, were compared between formalin-fixed and live R. montanensis samples. The experiments were performed in triplicate for each group, and the results are a combination of the results from two independent experiments. ****, P < 0.0001.