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Journal of Bacteriology, April 2000, p. 2245-2252, Vol. 182, No. 8
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

OmpR Regulates the Stationary-Phase Acid Tolerance Response of Salmonella enterica Serovar Typhimurium

Iel Soo Bang,1,2 Bae Hoon Kim,1 John W. Foster,2 and Yong Keun Park1,*

Graduate School of Biotechnology, Korea University, Seoul 136701, Korea,1 and Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile, Alabama 366882

Received 12 November 1999/Accepted 24 January 2000

Tolerance to acidic environments is an important property of free-living and pathogenic enteric bacteria. Salmonella enterica serovar Typhimurium possesses two general forms of inducible acid tolerance. One is evident in exponentially growing cells exposed to a sudden acid shock. The other is induced when stationary-phase cells are subjected to a similar shock. These log-phase and stationary-phase acid tolerance responses (ATRs) are distinct in that genes identified as participating in log-phase ATR have little to no effect on the stationary-phase ATR (I. S. Lee, J. L. Slouczewski, and J. W. Foster, J. Bacteriol. 176:1422-1426, 1994). An insertion mutagenesis strategy designed to reveal genes associated with acid-inducible stationary-phase acid tolerance (stationary-phase ATR) yielded two insertions in the response regulator gene ompR. The ompR mutants were defective in stationary-phase ATR but not log-phase ATR. EnvZ, the known cognate sensor kinase, and the porin genes known to be controlled by OmpR, ompC and ompF, were not required for stationary-phase ATR. However, the alternate phosphodonor acetyl phosphate appears to play a crucial role in OmpR-mediated stationary-phase ATR and in the OmpR-dependent acid induction of ompC. This conclusion was based on finding that a mutant form of OmpR, which is active even though it cannot be phosphorylated, was able to suppress the acid-sensitive phenotype of an ack pta mutant lacking acetyl phosphate. The data also revealed that acid shock increases the level of ompR message and protein in stationary-phase cells. Thus, it appears that acid shock induces the production of OmpR, which in its phosphorylated state can trigger expression of genes needed for acid-induced stationary-phase acid tolerance.

* Corresponding author. Mailing address: Graduate School of Biotechnology, Korea University, Seoul 136-701, Korea. Phone: 82-2-3290-3922. Fax: 82-2-927-9028. E-mail: ykpark{at}kucc08.korea.ac.kr.

Journal of Bacteriology, April 2000, p. 2245-2252, Vol. 182, No. 8
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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