a Structure of anguibactin and vanchrobactin. b Schematic map of the pJM1 virulence plasmid and chromosomal loci harboring genes involved in siderophore biosynthesis and transport. The location of two replication origins, ori1 and ori2, are highlighted as dark gray. Two well-characterized regions of pJM1, iron transport and biosynthesis operon (ITBO) as well as trans-acting factor (TAF) region composed of TAFb and TAFr, are highlighted as light gray. RS1, insertion sequence RS1 found in pJM1 and in the vabF gene on chromosome I