Logo of jbacterPermissionsJournals.ASM.orgJournalJB ArticleJournal InfoAuthorsReviewers
J Bacteriol. May 1996; 178(9): 2586–2592.
PMCID: PMC177983

PchR, a regulator of ferripyochelin receptor gene (fptA) expression in Pseudomonas aeruginosa, functions both as an activator and as a repressor.


The product of the pchR gene, an AraC-like regulatory protein, is required for production of the FptA ferric pyochelin receptor in response to iron limitation and pyochelin (D. E. Heinrichs and K. Poole, J. Bacteriol. 175:5882-5889, 1993). The influence of iron, pyochelin, PchR, and FptA on fptA and pchR gene expression was assessed with fptA-lacZ and pchR-lacZ transcriptional fusions. As was expected, the expression of fptA decreased dramatically following the inactivation of pchR by the insertion of an OmegaHg cartridge, although the effect (> 10-fold) was not as dramatic as that of pyochelin deficiency, which obviated fptA gene expression. Insertional inactivation of pchR in a pyochelin-deficient (Pch-) background restored fptA expression to levels observed in the pyochelin-producing (Pch+) PchR- strain, suggesting that PchR represses fptA expression in the absence of pyochelin. Consistent with this, the cloned gene caused a five-fold decrease in the expression of the fptA-lacZ fusion in Escherichia coli. pchR gene expression was inducible by iron limitation, a result in agreement with the previous identification of a Fur box upstream of the gene, although the magnitude of the induction was less than that observed for fptA in response to iron limitation. Expression of pchR was effectively absent in a pyochelin-deficient strain, and insertional inactivation of pchR in a Pch+ or Pch- background caused an increase in pchR gene expression. PchR, thus, negatively regulates its own expression. Two related heptameric sequences, CGAGGAA and CGTGGAT, were identified upstream of the putative -35 region of both fptA and pchR and may function as a binding site for PchR. Insertional inactivation of fptA caused a marked decrease in fptA expression in a Pch+ background and obviated the apparent repression of fptA expression in a Pch- background, reminiscent of the effect of a pchR mutation. The fptA mutant did not, however, exhibit a defect in pchR expression. Interestingly, fptA mutants were unable to grow in the presence of pyochelin, suggesting that FptA is the sole outer membrane receptor for ferric pyochelin. These data indicate that PchR functions as both an activator and a repressor in controlling the expression of fptA and pchR. The involvement of FptA in this control is unclear, although it may be important in mediating the pyochelin effect on fptA expression, possibly by modulating PchR activity.

Full Text

The Full Text of this article is available as a PDF (301K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Ankenbauer R, Hanne LF, Cox CD. Mapping of mutations in Pseudomonas aeruginosa defective in pyoverdin production. J Bacteriol. 1986 Jul;167(1):7–11. [PMC free article] [PubMed]
  • Ankenbauer R, Sriyosachati S, Cox CD. Effects of siderophores on the growth of Pseudomonas aeruginosa in human serum and transferrin. Infect Immun. 1985 Jul;49(1):132–140. [PMC free article] [PubMed]
  • Ankenbauer RG. Cloning of the outer membrane high-affinity Fe(III)-pyochelin receptor of Pseudomonas aeruginosa. J Bacteriol. 1992 Jul;174(13):4401–4409. [PMC free article] [PubMed]
  • Ankenbauer RG, Cox CD. Isolation and characterization of Pseudomonas aeruginosa mutants requiring salicylic acid for pyochelin biosynthesis. J Bacteriol. 1988 Nov;170(11):5364–5367. [PMC free article] [PubMed]
  • Ankenbauer RG, Quan HN. FptA, the Fe(III)-pyochelin receptor of Pseudomonas aeruginosa: a phenolate siderophore receptor homologous to hydroxamate siderophore receptors. J Bacteriol. 1994 Jan;176(2):307–319. [PMC free article] [PubMed]
  • Berry D, Kropinski AM. Effect of lipopolysaccharide mutations and temperature on plasmid transformation efficiency in Pseudomonas aeruginosa. Can J Microbiol. 1986 May;32(5):436–438. [PubMed]
  • Botzenhart K, Rüden H. Hospital infections caused by Pseudomonas aeruginosa. Antibiot Chemother (1971) 1987;39:1–15. [PubMed]
  • Britigan BE, Rasmussen GT, Cox CD. Pseudomonas siderophore pyochelin enhances neutrophil-mediated endothelial cell injury. Am J Physiol. 1994 Feb;266(2 Pt 1):L192–L198. [PubMed]
  • Britigan BE, Roeder TL, Rasmussen GT, Shasby DM, McCormick ML, Cox CD. Interaction of the Pseudomonas aeruginosa secretory products pyocyanin and pyochelin generates hydroxyl radical and causes synergistic damage to endothelial cells. Implications for Pseudomonas-associated tissue injury. J Clin Invest. 1992 Dec;90(6):2187–2196. [PMC free article] [PubMed]
  • Caron J, Coffield LM, Scott JR. A plasmid-encoded regulatory gene, rns, required for expression of the CS1 and CS2 adhesins of enterotoxigenic Escherichia coli. Proc Natl Acad Sci U S A. 1989 Feb;86(3):963–967. [PMC free article] [PubMed]
  • Casadaban MJ. Regulation of the regulatory gene for the arabinose pathway, araC. J Mol Biol. 1976 Jul 5;104(3):557–566. [PubMed]
  • Cornelis G, Sluiters C, de Rouvroit CL, Michiels T. Homology between virF, the transcriptional activator of the Yersinia virulence regulon, and AraC, the Escherichia coli arabinose operon regulator. J Bacteriol. 1989 Jan;171(1):254–262. [PMC free article] [PubMed]
  • Cornelis P, Moguilevsky N, Jacques JF, Masson PL. Study of the siderophores and receptors in different clinical isolates of Pseudomonas aeruginosa. Antibiot Chemother (1971) 1987;39:290–306. [PubMed]
  • Cox CD. Iron uptake with ferripyochelin and ferric citrate by Pseudomonas aeruginosa. J Bacteriol. 1980 May;142(2):581–587. [PMC free article] [PubMed]
  • Cox CD. Effect of pyochelin on the virulence of Pseudomonas aeruginosa. Infect Immun. 1982 Apr;36(1):17–23. [PMC free article] [PubMed]
  • Cox CD, Adams P. Siderophore activity of pyoverdin for Pseudomonas aeruginosa. Infect Immun. 1985 Apr;48(1):130–138. [PMC free article] [PubMed]
  • Crosa JH. The relationship of plasmid-mediated iron transport and bacterial virulence. Annu Rev Microbiol. 1984;38:69–89. [PubMed]
  • de Lorenzo V, Wee S, Herrero M, Neilands JB. Operator sequences of the aerobactin operon of plasmid ColV-K30 binding the ferric uptake regulation (fur) repressor. J Bacteriol. 1987 Jun;169(6):2624–2630. [PMC free article] [PubMed]
  • Fellay R, Frey J, Krisch H. Interposon mutagenesis of soil and water bacteria: a family of DNA fragments designed for in vitro insertional mutagenesis of gram-negative bacteria. Gene. 1987;52(2-3):147–154. [PubMed]
  • Gensberg K, Hughes K, Smith AW. Siderophore-specific induction of iron uptake in Pseudomonas aeruginosa. J Gen Microbiol. 1992 Nov;138(11):2381–2387. [PubMed]
  • Härle C, Kim I, Angerer A, Braun V. Signal transfer through three compartments: transcription initiation of the Escherichia coli ferric citrate transport system from the cell surface. EMBO J. 1995 Apr 3;14(7):1430–1438. [PMC free article] [PubMed]
  • Heinrichs DE, Poole K. Cloning and sequence analysis of a gene (pchR) encoding an AraC family activator of pyochelin and ferripyochelin receptor synthesis in Pseudomonas aeruginosa. J Bacteriol. 1993 Sep;175(18):5882–5889. [PMC free article] [PubMed]
  • Heinrichs DE, Young L, Poole K. Pyochelin-mediated iron transport in Pseudomonas aeruginosa: involvement of a high-molecular-mass outer membrane protein. Infect Immun. 1991 Oct;59(10):3680–3684. [PMC free article] [PubMed]
  • Higgins DE, Nazareno E, DiRita VJ. The virulence gene activator ToxT from Vibrio cholerae is a member of the AraC family of transcriptional activators. J Bacteriol. 1992 Nov;174(21):6974–6980. [PMC free article] [PubMed]
  • Inouye S, Nakazawa A, Nakazawa T. Nucleotide sequence of the regulatory gene xylS on the Pseudomonas putida TOL plasmid and identification of the protein product. Gene. 1986;44(2-3):235–242. [PubMed]
  • Jones RL, Peterson CM, Grady RW, Kumbaraci T, Cerami A, Graziano JH. Effects of iron chelators and iron overload on Salmonella infection. Nature. 1977 May 5;267(5606):63–65. [PubMed]
  • Kessler B, Herrero M, Timmis KN, de Lorenzo V. Genetic evidence that the XylS regulator of the Pseudomonas TOL meta operon controls the Pm promoter through weak DNA-protein interactions. J Bacteriol. 1994 Jun;176(11):3171–3176. [PMC free article] [PubMed]
  • Khimji PL, Miles AA. Microbial iron-chelators and their action on Klebsiella infections in the skin of guinea-pigs. Br J Exp Pathol. 1978 Apr;59(2):137–147. [PMC free article] [PubMed]
  • Koster M, van Klompenburg W, Bitter W, Leong J, Weisbeek P. Role for the outer membrane ferric siderophore receptor PupB in signal transduction across the bacterial cell envelope. EMBO J. 1994 Jun 15;13(12):2805–2813. [PMC free article] [PubMed]
  • Lee N, Francklyn C, Hamilton EP. Arabinose-induced binding of AraC protein to araI2 activates the araBAD operon promoter. Proc Natl Acad Sci U S A. 1987 Dec;84(24):8814–8818. [PMC free article] [PubMed]
  • Lobell RB, Schleif RF. DNA looping and unlooping by AraC protein. Science. 1990 Oct 26;250(4980):528–532. [PubMed]
  • Menon KP, Lee NL. Activation of ara operons by a truncated AraC protein does not require inducer. Proc Natl Acad Sci U S A. 1990 May;87(10):3708–3712. [PMC free article] [PubMed]
  • Neilands JB. Iron absorption and transport in microorganisms. Annu Rev Nutr. 1981;1:27–46. [PubMed]
  • Neilands JB. Microbial iron compounds. Annu Rev Biochem. 1981;50:715–731. [PubMed]
  • Poole K, Young L, Neshat S. Enterobactin-mediated iron transport in Pseudomonas aeruginosa. J Bacteriol. 1990 Dec;172(12):6991–6996. [PMC free article] [PubMed]
  • Raibaud O, Schwartz M. Positive control of transcription initiation in bacteria. Annu Rev Genet. 1984;18:173–206. [PubMed]
  • Ramos JL, Rojo F, Zhou L, Timmis KN. A family of positive regulators related to the Pseudomonas putida TOL plasmid XylS and the Escherichia coli AraC activators. Nucleic Acids Res. 1990 Apr 25;18(8):2149–2152. [PMC free article] [PubMed]
  • Schweizer HP. Escherichia-Pseudomonas shuttle vectors derived from pUC18/19. Gene. 1991 Jan 2;97(1):109–121. [PubMed]
  • Sokol PA, Woods DE. Demonstration of an iron-siderophore-binding protein in the outer membrane of Pseudomonas aeruginosa. Infect Immun. 1983 May;40(2):665–669. [PMC free article] [PubMed]
  • Sriyosachati S, Cox CD. Siderophore-mediated iron acquisition from transferrin by Pseudomonas aeruginosa. Infect Immun. 1986 Jun;52(3):885–891. [PMC free article] [PubMed]
  • Vieira J, Messing J. The pUC plasmids, an M13mp7-derived system for insertion mutagenesis and sequencing with synthetic universal primers. Gene. 1982 Oct;19(3):259–268. [PubMed]
  • Wallace RG, Lee N, Fowler AV. The araC gene of Escherichia coli: transcriptional and translational start-points and complete nucleotide sequence. Gene. 1980 Dec;12(3-4):179–190. [PubMed]
  • Wattiau P, Cornelis GR. Identification of DNA sequences recognized by VirF, the transcriptional activator of the Yersinia yop regulon. J Bacteriol. 1994 Jul;176(13):3878–3884. [PMC free article] [PubMed]
  • Zimmermann L, Hantke K, Braun V. Exogenous induction of the iron dicitrate transport system of Escherichia coli K-12. J Bacteriol. 1984 Jul;159(1):271–277. [PMC free article] [PubMed]

Articles from Journal of Bacteriology are provided here courtesy of American Society for Microbiology (ASM)


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...