PVD gene activities in response to iron. The activities of pvdL, pvdS, fpvA, fpvI and fpvR in response to iron were determined from 'lacZ reporter fusion strains, TR107.2.1, TR107.1.1, TR135.1.1, TR107.4.1, and TR107.5.1, respectively. β-galactosidase activity (fmol 4 MU/min/cell) was assayed for cells growing in CAA media supplemented with 100 μM 2,2'-dipyridyl (black bars), 450 nM FeSO4 (hatched bars), and 450 μM FeSO4 (white bars). Data are the means ± the standard errors of four independent experiments for each strain. Asterisks indicate that the promoter activity in the given iron treatment (100 μM 2,2'-dipyridyl or 450 nM FeSO4) was significantly different to the background activity in 450 μM FeSO4 at the P = 0.05 level of significance using Dunnett's method.