FIG 9.

Expression and contribution of the Sht-family proteins in complement resistance. (A) Bacterial survival, determined as the percent CFU per milliliter relative to input of WT (white) and Δsht ΔshtII (black) mutant strains after 3 h of incubation in whole blood or heat-inactivated blood. The results represent means ± the standard deviations of three independent experiments. (B and C) Transcription of sht (B) and shtII (C) after 90 min of incubation in zinc-restricted CDM (black), CDM supplemented with 10 μM Zn²⁺ (white), or heat-inactivated serum (gray). Transcripts of each gene were normalized to recA with a reference value of 100 for sht and shtII transcripts after bacterial growth in zinc-restricted CDM. The results are means ± the standard deviations from three independent experiments. The statistical significance of the differences was determined by a two-tailed unpaired Student t test comparing gene expression levels to the zinc-restricted CDM control (*, P < 0.05; **, P < 0.01; ***, P < 0.005).