Table 2.

Siderophore production by wild-type 518, urbs1 gene disruption mutant UMC015, and urbs1 NTG mutants carrying a single amino acid mutation in the C-terminal finger domain under low and high iron conditions

Strain	Low iron	High iron	LI/HI
518	0.12  ±  0.08*	0.01  ±  0.005	12
UMC015	0.16  ±  0.02	0.05  ±  0.01	3.2
UMC002-1 (urbs1-1)	0.14  ±  0.08	0.06  ±  0.02	2.3
UMC005-1 (urbs1-2)	0.16  ±  0.01	0.01  ±  0.00	16
UMC007-1 (urbs1-3)	0.14  ±  0.02	0.04  ±  0.01	3.5

Cells were grown for 48 h at 28°C in low iron medium with or without 10 μM FeSO₄. Siderophore production was determined by the ferric perchlorate assay as described. Equal volumes of cell free supernatant and assay solution were mixed and the adsorbance read at 495 nm. Data were normalized to cell growth using an adsorbance at 600 nm equal to 1.0. LI, low iron; HI, high iron. 

^*Means of three replications ± SE.