Journal of Molecular Evolution

, Volume 60, Issue 4, pp 462–474 | Cite as

Comparison of the PhoPQ Regulon in Escherichia coli and Salmonella typhimurium

  • Pieter Monsieurs
  • Sigrid De Keersmaecker
  • William W. Navarre
  • Martin W. Bader
  • Frank De Smet
  • Michael McClelland
  • Ferric C. Fang
  • Bart De Moor
  • Jos Vanderleyden
  • Kathleen MarchalEmail author


The PhoPQ two-component system acts as a transcriptional regulator that responds to Mg2+ starvation both in Escherichia coli and Salmonella typhimurium (Garcia et al. 1996; Kato et al. 1999). By monitoring the availability of extracellular Mg2+, this two-component system allows S. typhimurium to sense the transition from an extracellular environment to a subcellular location. Concomitantly with this transition, a set of virulence factors essential for survival in the intracellular environment is activated by the PhoPQ system (Groisman et al. 1989; Miller et al. 1989). Compared to nonpathogenic strains, such as E. coli K12, the PhoPQ regulon in pathogens must contain target genes specifically contributing to the virulence phenotype. To verify this hypothesis, we compared the composition of the PhoPQ regulon between E. coli and S. typhimurium using a combination of expression experiments and motif data. PhoPQ-dependent genes in both organisms were identified from PhoPQ-related microarray experiments. To distinguish between direct and indirect targets, we searched for the presence of the regulatory motif in the promoter region of the identified PhoPQ-dependent genes. This allowed us to reconstruct the direct PhoPQ-dependent regulons in E. coli K12 and S. typhimurium LT2. Comparison of both regulons revealed a very limited overlap of PhoPQ-dependent genes between both organisms. These results suggest that the PhoPQ system has acquired a specialized function during evolution in each of these closely related species that allows adaptation to the specificities of their lifestyles (e.g., pathogenesis in S. typhimurium).


PhoPQ regulon Escherichia coli Salmonella typhimirium Genome evolution Comparative genomics 



K. Marchal is a postdoctoral researcher of the Belgian Fund for Scientific Research (FWO-Vlaanderen). This work was partially supported by (1) IWT projects STWW-00162 and GBOU-SQUAD-20160; (2) Research Council KULeuven GOA Mefisto-666, GOA-Ambiorics, and IDO genetic networks; (3) FWO projects G.0115.01 and G.0413.03; and (4) IUAP V-22 (2002–2006). The authors like to thank Gert Thijs for the help with motif detection.


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Copyright information

© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  • Pieter Monsieurs
    • 1
  • Sigrid De Keersmaecker
    • 2
  • William W. Navarre
    • 3
  • Martin W. Bader
    • 4
  • Frank De Smet
    • 1
  • Michael McClelland
    • 5
  • Ferric C. Fang
    • 3
    • 4
  • Bart De Moor
    • 1
  • Jos Vanderleyden
    • 2
  • Kathleen Marchal
    • 2
    • 1
    Email author
  1. 1.ESAT-SCDLeuven-HeverleeBelgium
  2. 2.Centre of Microbial and Plant GeneticsLeuven-HeverleeBelgium
  3. 3.Department of Laboratory MedicineUniversity of WashingtonSeattleUSA
  4. 4.Department of MicrobiologyUniversity of WashingtonSeattleUSA
  5. 5.Sidney Kimmel Cancer CenterSan DiegoUSA

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