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Journal of Bacteriology, December 2009, p. 7174-7181, Vol. 191, No. 23
0021-9193/09/$08.00+0     doi:10.1128/JB.00958-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Activated by Different Signals, the PhoP/PhoQ Two-Component System Differentially Regulates Metal Uptake{triangledown} ,{dagger}

Eunna Choi,1 Eduardo A. Groisman,2 and Dongwoo Shin1*

Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, South Korea,1 Department of Molecular Microbiology, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 631102

Received 21 July 2009/ Accepted 19 September 2009

The PhoP/PhoQ two-component system controls several physiological and virulence functions in Salmonella enterica. This system is activated by low Mg2+, acidic pH, and antimicrobial peptides, but the biological consequences resulting from sensing multiple signals are presently unclear. Here, we report that the PhoP/PhoQ system regulates different Salmonella genes depending on whether the inducing signal is acidic pH or low Mg2+. When Salmonella experiences acidic pH, the PhoP/PhoQ system promotes Fe2+ uptake in a process that requires the response regulator RstA, activating transcription of the Fe2+ transporter gene feoB. In contrast, the PhoP-induced RstA protein did not promote feoB expression at neutral pH with low Mg2+. The PhoP/PhoQ system promotes the expression of the Mg2+ transporter mgtA gene only when activated in bacteria starved for Mg2+. This is because mgtA transcription promoted at high Mg2+ concentrations by the acidic-pH-activated PhoP protein failed to reach the mgtA coding region due to the mgtA leader region functioning as a Mg2+ sensor. Our results show that a single two-component regulatory system can regulate distinct sets of genes in response to different input signals.

* Corresponding author. Mailing address: Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, 300 Chunchun-dong, Jangan-gu, Suwon 440-746, South Korea. Phone: 82-31-299-6224. Fax: 82-31-299-6229. E-mail: dshin{at}med.skku.ac.kr

{triangledown} Published ahead of print on 2 October 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, December 2009, p. 7174-7181, Vol. 191, No. 23
0021-9193/09/$08.00+0     doi:10.1128/JB.00958-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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