FIG 4.

mdaB and nfrA respond to structurally diverse quinones and flavins. (a to c) Expression levels of mdaB and rrpA (a), mdaB in the ΔrrpA mutant strain 15 min after treatment with 100 μM quinones (b), and nfrA and rrpB 15 min after treatment with 100 μM flavins (c). (d and e) Growth in brucella broth was determined by measuring the OD₆₀₀ every 15 min after addition of 100 μM 2-hydroxy-1,4-naphthoquinone to the 11168H, ΔrrpA, and ΔmdaB strains (d) and 500 μM riboflavin to the 11168H, ΔrrpB, and ΔnfrA strains at an OD₆₀₀ of ∼0.45 (e). (f and g) Cell viability was determined 60 min and 120 min after treatment with 100 μM 2-hydroxy-1,4-naphthoquinone (f) and 500 μM riboflavin (g). Gene expression was determined by real-time RT-qPCR after treatment with compounds and is displayed relative to the value of the control expression, after normalization with gyrA expression. The values are the means of at least three independent experiments. Error bars = SD. *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001.