The siderophore system is essential for viability of Aspergillus nidulans: functional analysis of two genes encoding l-ornithine N 5-monooxygenase (sidA) and a non-ribosomal peptide synthetase (sidC)

Mol Microbiol. 2003 Jul;49(2):359-75. doi: 10.1046/j.1365-2958.2003.03586.x.


The filamentous ascomycete A. nidulans produces two major siderophores: it excretes triacetylfusarinine C to capture iron and contains ferricrocin intracellularly. In this study we report the characterization of two siderophore biosynthetic genes, sidA encoding l-ornithine N(5)-monooxygenase and sidC encoding a non-ribosomal peptide synthetase respectively. Disruption of sidC eliminated synthesis of ferricrocin and deletion of sidA completely blocked siderophore biosynthesis. Siderophore-deficient strains were unable to grow, unless the growth medium was supplemented with siderophores, suggesting that the siderophore system is the major iron assimilatory system of A. nidulans during both iron depleted and iron-replete conditions. Partial restoration of the growth of siderophore-deficient mutants by high concentrations of Fe(2+) (but not Fe(3+)) indicates the presence of an additional ferrous transport system and the absence of an efficient reductive iron assmilatory system. Uptake studies demonstrated that TAFC-bound iron is transferred to cellular ferricrocin whereas ferricrocin is stored after uptake. The siderophore-deficient mutant was able to synthesize ferricrocin from triacetylfusarinine C. Ferricrocin-deficiency caused an increased intracellular labile iron pool, upregulation of antioxidative enzymes and elevated sensitivity to the redox cycler paraquat. This indicates that the lack of this cellular iron storage compound causes oxidative stress. Moreover, ferricrocin biosynthesis was found to be crucial for efficient conidiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Aspergillus nidulans / cytology
  • Aspergillus nidulans / enzymology*
  • Aspergillus nidulans / genetics
  • Aspergillus nidulans / physiology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cell Survival / physiology*
  • Ferrichrome / analogs & derivatives*
  • Ferrichrome / chemistry
  • Ferrichrome / metabolism
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Herbicides / metabolism
  • Hydroxamic Acids / chemistry
  • Hydroxamic Acids / metabolism
  • Iron / metabolism
  • Mixed Function Oxygenases / genetics*
  • Mixed Function Oxygenases / metabolism*
  • Molecular Sequence Data
  • Molecular Structure
  • Paraquat / metabolism
  • Peptide Synthases / genetics*
  • Peptide Synthases / metabolism*
  • Sequence Alignment
  • Siderophores / metabolism*


  • Bacterial Proteins
  • Fungal Proteins
  • Herbicides
  • Hydroxamic Acids
  • Siderophores
  • fusarinine
  • Ferrichrome
  • ferricrocin
  • Iron
  • Mixed Function Oxygenases
  • ornithine N5-oxygenase
  • Peptide Synthases
  • non-ribosomal peptide synthase
  • Paraquat