BACILLUS-SUBTILIS CONTAINS MULTIPLE FUR HOMOLOGS - IDENTIFICATION OF THE IRON UPTAKE (FUR) AND PEROXIDE REGULON (PERR) REPRESSORS

Fur (ferric uptake regulator) proteins control iron uptake in many Gra m-negative bacteria. Although Fur homologues have been identified in G ram-positive bacteria, their roles in gene regulation are unknown. Gen ome sequencing has revealed three fur homologues in Bacillus subtilis: yqkL, yqfV and ygaG. We demonstrate that yqkL encodes an iron uptake repressor: both siderophore biosynthesis and transcription of ferri-si derophore uptake genes is constitutive in the yqkL mutant. Thus, yqkL encodes a repressor that is functionally as well as structurally relat ed to Fur. B. subtilis peroxide stress genes are induced by either H2O 2 or by metal ion limitation. Previous genetic studies defined a regul atory locus, perR, postulated to encode the peroxide regulon repressor . We demonstrate that a ygaG mutant has the perR phenotype: it is high ly resistant to peroxides and overexpresses catalase, alkyl hydroperox ide reductase and the DNA binding protein MrgA. Nine spontaneous perR mutations, isolated by virtue of their ability to derepress mrgA trans cription in the presence of manganous ion, all contain sequence change s in the ygaG locus and can be complemented by the cloned ygaG gene. T hus, ygaG encodes the peroxide regulon repressor and is allelic with p erR.