The sensitivity of R. anatipestifer CH-1 and its fur mutant to streptonigrin. The R. anatipestifer CH-1pLMF03, R. anatipestifer CH-1ΔfurpLMF03 and R. anatipestifer CH-1ΔfurpLMF03::fur strains were grown in GCB medium with no addition (A), with 100 μM EDDHA (B) or with 100 μM EDDHA and 200 μM Fe(NO3)3 (C) at 37 °C in a shaking incubator to the exponential phase (OD = 1.0–1.5). The bacteria were collected and suspended in PBS at 0.5 OD/mL, and were exposed to streptonigrin (50 ng/mL and 80 ng/mL) for 30 min. The survival rate of each culture was determined as described in the “Materials and methods”. The error bars represent the standard deviations of three independent experiments and three replicate samples for each experiment. Statistical significance was determined using two-way ANOVA (****P < 0.0001, ** P < 0.01, * P < 0.05).