Fig 3.
Citrate addition affects expression of a Fur-regulated reporter. Shown is β-galactosidase reporter activity for wild-type and Δfur mutant V. fischeri strains with the Fur-dependent PVF_1225-lacZ reporter plasmid pAKD912 grown in SWTO medium supplemented with 43 μM FeSO4 without further additions or supplemented with 20 mM citrate or with 20 mM citrate and 2 mM additional FeSO4. Cells were harvested at an OD595 of ∼1.0. The asterisk indicates a significant difference from other medium conditions within a strain (P < 0.001), based on an analysis of variance and Tukey's honestly significant difference test. Data are representative of at least three independent experiments. Error bars indicate standard deviations (n = 2).