Fig 2. Sef1 is required for growth and riboflavin secretion in iron-depleted medium.

(A) The wild-type strain SC5314, heterozygous and homozygous sef1Δ mutants, and complemented strains in which a wild-type SEF1 copy was reinserted into the homozygous (sef1Δ/sef1Δ + SEF1) or heterozygous (SEF1/sef1Δ + SEF1) mutants were grown in minimal medium with (+ FeCl₃) or without iron (+ BPS). Cultures were photographed after 4 days of growth at 30°C. The two independently generated series of strains behaved identically and only one of them is shown. (B) The optical densities of the cultures were determined; shown are the means and standard deviations of three independent cultures of each strain. Results for both independently generated series of strains are shown separately; data were combined for statistical analysis. Significant differences from the wild type are indicated by stars (***, p < 0.001; **, p < 0.01).