Transcription ofnhaA, the Main Na+/H+Antiporter ofEscherichia coli, Is Regulated by Na+and Growth Phase

Dover, Nir; Padan, Etana

doi:10.1128/jb.183.2.644-653.2001

Cited by 47 publications

(34 citation statements)

References 35 publications

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“…Here we demonstrate that CsrA regulates the translation of nhaR, encoding the LTTR protein NhaR, which responds to elevated [Na ϩ ] and alkaline pH conditions (19). NhaR is important for biofilm formation in E. coli K-12, as it activates the transcription of the pgaABCD genes (26), which is essential for the synthesis and secretion of the biofilm adhesin PGA (30,62).…”

Section: Discussionmentioning

confidence: 99%

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Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA

Pannuri

Yakhnin

Vakulskas

et al. 2011

Journal of Bacteriology

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The RNA binding protein CsrA (RsmA) represses biofilm formation in several proteobacterial species. In Escherichia coli, it represses the production of the polysaccharide adhesin poly-␤-1,6-N-acetyl-D-glucosamine (PGA) by binding to the pgaABCD mRNA leader, inhibiting pgaA translation, and destabilizing this transcript. In addition, CsrA represses genes responsible for the synthesis of cyclic di-GMP, an activator of PGA production. Here we determined that CsrA also represses NhaR, a LysR-type transcriptional regulator which responds to elevated [Na ؉ ] and alkaline pH and activates the transcription of the pgaABCD operon. Gel shift studies revealed that CsrA binds at two sites in the 5= untranslated segment of nhaR, one of which overlaps the Shine-Dalgarno sequence. An epitope-tagged NhaR protein, expressed from the nhaR chromosomal locus, and an nhaR posttranscriptional reporter fusion (PlacUV5-nhaR=-=lacZ) both showed robust repression by CsrA. Northern blotting revealed a complex transcription pattern for the nhaAR locus. Nevertheless, CsrA did not repress nhaR mRNA levels. Toeprinting assays showed that CsrA competes effectively with the ribosome for binding to the translation initiation region of nhaR. Together, these findings indicate that CsrA blocks nhaR translation. Epistasis studies with a pgaA-lacZ transcriptional fusion confirmed a model in which CsrA indirectly represses pgaABCD transcription via NhaR. We conclude that CsrA regulates the horizontally acquired pgaABCD operon and PGA biosynthesis at multiple levels. Furthermore, nhaR repression exemplifies an expanding role for CsrA as a global regulator of stress response systems.

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Section: Discussionmentioning

confidence: 99%

“…The nhaAp1 promoter is repressed by H-NS, whereas NhaR relieves H-NS-mediated silencing under alkaline pH and in the presence of Na ϩ (12,20). The nhaAp2 promoter requires the general stress sigma factor S for transcription (19) (Fig. 1).…”

mentioning

confidence: 99%

Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA

Pannuri

Yakhnin

Vakulskas

et al. 2011

Journal of Bacteriology

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“…nhaA encodes a Na ϩ /H ϩ antiporter that is essential for survival in alkaline media (33). Expression of nhaA is induced by nhaR, which stimulates RpoD binding to the nhaA promoter (9). In alkaline environments up to pH 7.9, this antiporter helps maintain pH homeostasis (33,37).…”

Section: Discussionmentioning

confidence: 99%

“…In fact, rpoS null mutants are quickly out-competed by wild-type cells during longterm stationary-phase incubation (M. J. Farrell and S. E. Finkel, unpublished data). Two RpoS-regulated genes that are known to be required for either competitive fitness or survival in stationary phase are dps and nhaA (1,9,28). dps encodes a nonspecific DNA binding protein involved in protecting the cell from many stresses (1,50).…”

Section: Discussionmentioning

confidence: 99%

The Growth Advantage in Stationary-Phase PhenotypeConferred by rpoS Mutations Is Dependent on the pH andNutrientEnvironment

2003

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Escherichia coli cells that are aged in batch culture display an increased fitness referred to as the growth advantage in stationary phase, or GASP, phenotype. A common early adaptation to this culture environment is a mutant rpoS allele, such as rpoS819, that results in attenuated RpoS activity. However, it is important to note that during long-term batch culture, environmental conditions are in flux. To date, most studies of the GASP phenotype have focused on identifying alleles that render an advantage in a specific environment, Luria-Bertani broth (LB) batch culture. To determine what role environmental conditions play in rendering relative fitness advantages to E. coli cells carrying either the wild-type or rpoS819 alleles, we performed competitions under a variety of culture conditions in which either the available nutrients, the pH, or both were manipulated. In LB medium, we found that while the rpoS819 allele confers a strong competitive fitness advantage at basic pH, it confers a reduced advantage under neutral conditions, and it is disadvantageous under acidic conditions. Similar results were found using other media. rpoS819 conferred its greatest advantage in basic minimal medium in which either glucose or Casamino Acids were the sole source of carbon and energy. In acidic medium supplemented with either Casamino Acids or glucose, the wild-type allele conferred a slight advantage. In addition, populations were dynamic under all pH conditions tested, with neither the wild-type nor mutant rpoS alleles sweeping a culture. We also found that the strength of the fitness advantage gained during a 10-day incubation is pH dependent.

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“…NhaA shows more activity than NhaB at pH 7.4 and above (Seo, 1998). The genetic expression of nhaA is regulated by two different genetic promoters: P1, in conjunction with NhaR and Na ϩ is activated when cells are in log phase; P2, in conjunction with the sigma factor, is activated in stationary phase cells (Dover & Padan, 2001). Others have suggested that NhaA activity is more dependent on the Na ϩ concentration inside the cell, rather than alkaline pH, and functions in a supporting role to other Na ϩ /H ϩ antiporters (Shijuku et al, 2001).…”

Section: Role Of Sodiummentioning

confidence: 99%

Habituation of Foodborne Pathogens Exposed to Extreme pH Conditions: Genetic Basis and Implications in Foods and Food Processing Environments

Sharma

Taormina²,

Beuchat

2003

FSTR

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Foodborne microorganisms capable of causing human diseases are exposed to a wide range of physical and chemical stresses in the environment. Exposure of cells to extreme, yet sublethal, preharvest and postharvest conditions can result in habituation or adaptation, which may subsequently afford protection against otherwise lethal stresses. The genetic basis for production of acid-shock proteins and heat-shock proteins as well as other intracellular and extracellular factors that play a role in the development of tolerance and cross protection to environmental stresses has been studied extensively, the focus largely being directed toward Escherichia coli and Salmonella. Less is known about habituation of other foodborne pathogens and spoilage microorganisms in extreme alkaline environments. Exposure of cells to sublethal concentrations of alkaline cleaners and sanitizers routinely used in food processing plants, for example, creates conditions for alkaline habituation which may result in cross protection against heat or other pasteurization or preservation technologies used in the food industry. This paper briefly reviews the genetic basis for development of tolerance of foodborne pathogens to extreme pH conditions and discusses some of the practical implications in foods and food processing environments.

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Transcription ofnhaA, the Main Na⁺/H⁺Antiporter ofEscherichia coli, Is Regulated by Na⁺and Growth Phase

Cited by 47 publications

References 35 publications

Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA

Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA

The Growth Advantage in Stationary-Phase PhenotypeConferred by rpoS Mutations Is Dependent on the pH andNutrientEnvironment

Habituation of Foodborne Pathogens Exposed to Extreme pH Conditions: Genetic Basis and Implications in Foods and Food Processing Environments

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