FIG 3.

The sch locus is responsible for detectable siderophore production. Siderophore production was quantified by liquid chrome azurol S (CAS) assay on bacterial supernatants. Bacteria were cultured overnight in M9 minimal medium with or without 36 μM FeSO₄. EDTA (10 μM) served as the positive control for iron limitation. Low absorbance (A₆₃₀) values indicate more siderophore production. Data are the means of three independent replicates, and error bars represent standard errors of the means. Significant differences (**, P < 0.01; ***, P < 0.001; ****, P < 0.0001) were determined using a two-tailed unpaired t test.