FIG. 2.

B. abortus ahpCD mutants display an increased sensitivity to endogenous H₂O₂ produced by the redox cycling activity of paraquat. Zones of inhibition for B. abortus 2308, KH2 (2308 katE), KH16 (2308 ahpCD), KK21 (2308 ahpCD katE), KH16 (pKHS6), and KK21 (pKHS6) around disks containing 0.5 M paraquat on Schaedler agar (A) or Schaedler agar supplemented with 7,800 U/ml bovine catalase (B). The data presented are means and standard deviations for triplicate determinations for each strain in a single experiment. The data presented here are representative of multiple (≥4) experiments performed from which equivalent results and statistical trends were obtained. Statistical significance (P ≤ 0.05) as determined by the Student two-tailed t test for comparisons of 2308 versus the other strains is represented by an asterisk (*).