Contribution of the Shigella flexneri Sit, Iuc, and Feo iron acquisition systems to iron acquisition in vitro and in cultured cells

Infect Immun. 2003 Apr;71(4):1919-28. doi: 10.1128/IAI.71.4.1919-1928.2003.


Shigella flexneri possesses multiple iron acquisition systems, including proteins involved in the synthesis and uptake of siderophores and the Feo system for ferrous iron utilization. We identified an additional S. flexneri putative iron transport gene, sitA, in a screen for S. flexneri genes that are induced in the eukaryotic intracellular environment. sitA was present in all Shigella species and in most enteroinvasive Escherichia coli strains but not in any other E. coli isolates tested. The sit locus consists of four genes encoding a potential ABC transport system. The deduced amino acid sequence of the S. flexneri sit locus was homologous to the Salmonella enterica serovar Typhimurium Sit and Yersinia pestis Yfe systems, which mediate both manganese and iron transport. The S. flexneri sit promoter was repressed by either iron or manganese, and the iron repression was partially dependent upon Fur. A sitA::cam mutation was constructed in S. flexneri. The sitA mutant showed reduced growth, relative to the wild type, in Luria broth containing an iron chelator but formed wild-type plaques on Henle cell monolayers, indicating that the sitA mutant was able to acquire iron and/or manganese in the host cell. However, mutants defective in two of these iron acquisition systems (sitA iucD, sitA feoB, and feoB iucD) formed slightly smaller plaques on Henle cell monolayers. A strain carrying mutations in sitA, feoB, and iucD did not form plaques on Henle cell monolayers.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism
  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Cells, Cultured
  • Gene Expression Regulation, Bacterial
  • Humans
  • Iron / metabolism*
  • Loop of Henle / cytology
  • Loop of Henle / microbiology
  • Manganese / metabolism
  • Mixed Function Oxygenases / genetics
  • Mixed Function Oxygenases / metabolism
  • Molecular Sequence Data
  • Shigella flexneri / genetics
  • Shigella flexneri / growth & development
  • Shigella flexneri / metabolism*


  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Cation Transport Proteins
  • FeoB protein, Helicobacter pylori
  • SitA protein, Shigella flexneri
  • Manganese
  • Iron
  • Mixed Function Oxygenases
  • lysine N-epsilon hydroxylase

Associated data

  • GENBANK/AY126440