Fig 2. Induction and inhibition of hypermutation by zinc in various strains of bacteria.

For each panel, the bacterial strain indicated was treated for 3 hours with and without the concentration of ciprofloxacin indicated, as guided by the ciprofloxacin MIC for each strain, and ± 0.2 mM zinc acetate. Then serial dilutions were performed, and plated on plain LB agar to determine the total number of bacteria, and on LB + rifampin, to determine the number of rifampin resistant colonies per mL. The rifampin resistance frequency was calculated for each condition. The rifampin concentrations, for each strain were, in μg/mL: Popeye-1, 12; B171-8, 8; CP9, 8; and Kpneu_707, 45. Paired ANOVA was by Kruskal- Wallis for non-parametric data due to skewing.