Table 2. Hfq is required for normal siderophore production.

	Total iron concentration in the growth medium
Strain (genotype)	0.37 µM	37 µM
2011 (wild type)	0.57±0.03 a	0.11±0.01 a
20PS01 (Δhfq)	0.74±0.04 b	0.06±0.01 b

The results are presented as siderophore relative units measured by the CAS interference assay [35]. Values represent the average of three independent cultures ± SD. Different letters indicate statistically significant differences among strains based on pairwise comparisons (Student’s t-test, P<0.05.).