FIGURE 2. Changes in mRNA and protein levels of S18-1 and S18-2 with varied zinc concentrations.

A. Growth curves of M. tuberculosis H37Rv. Aliquots were sampled for analysis at different growth stages as labeled: EL-early logarithmic, L-logarithmic, and S-stationary phase (dashed black line - 7H9/ADC, grey solid line - Sauton's medium, black solid line - Sauton's with 6 μM ZnSO₄)

B, D, E. Quantification of mRNA: qRT-PCR of specific mRNA for genes encoding S18-2 (B), S18-1 (D), and S6 proteins (E) normalized to 16S rRNA in M. tuberculosis grown in 7H9/ADC or Sauton's medium prepared with or without added ZnSO₄, as indicated in panel A.

C. ELISA quantification of S18-2 protein in total protein preparations. Relative luminescence is fold change over the background.

F. Mass spectrometry quantification of S18 proteins at stationary growth phase. Spectral count (s.c.) for identified peptides normalized against s.c. of all identified ribosomal proteins.

G. Normalized specific mRNA quantified by qRT-PCR at stationary growth phase. Data from panels B and D shown to highlight effects of Zn²⁺ on S18 gene expression.

Error bars in all graphs are ±1 standard deviation of technical replicates.