FIG 3.
R. typhiGFPuv bacteria are viable and stably express the gfp transgene in the presence of rifampin. (A) Tissue culture flasks (25 cm2) with irradiated L929 cells were inoculated with comparable numbers of R. typhiGFPuv (rec) (n = 2) and wild-type R. typhi (wt) (n = 2) bacteria (0.5 copies per cell). The cells were cultured in the presence or absence of 10 ng/ml rifampin (rif). R. typhi prsA-specific (PrsA) and gfp-specific (GFP) qPCRs were performed at the indicated time points (x axis) with 10 ng of cell culture DNA. The y axis shows the log10 copy numbers per 10 ng DNA. (B) R. typhiGFPuv bacteria were passaged weekly into fresh L929 cell cultures in 25-cm2 tissue culture flasks in the absence or presence of the indicated amounts of rifampin (x axis). DNA was prepared from the cultures after 3 and 6 passages and analyzed for the content of bacteria and the gfp transgene (y axis) by prsA-specific (PrsA) and gfp-specific (GFP) qPCR.