micF antisense RNA has a major role in osmoregulation of OmpF in Escherichia coli

Ramani, Natarajan; Hedeshian, Mohir; Freundlich, Martin

doi:10.1128/jb.176.16.5005-5010.1994

Cited by 50 publications

(41 citation statements)

References 48 publications

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“…In contrast to that of nearly all other osmotically regulated systems in E. coli, the osmotic control of s occurs at the posttranscriptional level (to our knowledge, the only other posttranscriptional osmoregulation is that of ompF by the micF antisense RNA during a shift from low to intermediate osmolarity [30]). In the case of s , increased translation and inhibition of s turnover contribute to osmotic induction (Fig.…”

Section: Discussionmentioning

confidence: 98%

Posttranscriptional osmotic regulation of the sigma(s) subunit of RNA polymerase in Escherichia coli

et al. 1996

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The s subunit of RNA polymerase (encoded by the rpoS gene) is a master regulator in a complex regulatory network that governs the expression of many stationary-phase-induced and osmotically regulated genes in Escherichia coli. rpoS expression is itself osmotically regulated by a mechanism that operates at the posttranscriptional level. Cells growing at high osmolarity already exhibit increased levels of s during the exponential phase of growth. Osmotic induction of rpoS can be triggered by addition of NaCl or sucrose and is alleviated by glycine betaine. Stimulation of rpoS translation and a change in the half-life of s from 3 to 50 min both contribute to osmotic induction. Experiments with lacZ fusions inserted at different positions within the rpoS gene indicate that an element required for s degradation is encoded between nucleotides 379 and 742 of the rpoS coding sequence.Like most single-cell organisms, bacteria must be able to cope with extreme fluctuations in the composition and physical parameters of their environments. One of these parameters is the osmolarity of the surrounding medium. When Escherichia coli cells experience a shift to high osmolarity, influx of potassium ions and synthesis of glutamate are strongly stimulated. This rapid response is followed by uptake from the medium and/or synthesis of compatible solutes and osmoprotectants like glycine betaine, proline, or trehalose (for a review, see reference 5). In parallel, the induction of numerous proteins can be observed by two-dimensional O'Farrell gel electrophoresis (4, 14). Several corresponding genes have been identified, for instance, by isolating hyperosmotically inducible lacZ or phoA gene fusions (1,3,6,(8)(9)(10)35).With respect to the regulatory mechanisms involved, two systems have been studied in detail. One is the proU operon, which encodes a glycine betaine uptake system (for a recent review, see reference 24), whereas the other is the ompF/ompC porin system, which is controlled by a typical two-component regulatory system consisting of the membrane-bound sensory histidine kinase EnvZ and the response regulatory OmpR (15,17,26,27). However, the regulatory mechanisms involved do not seem to play a general role in the osmotic regulation of many genes, and efforts to identify a global osmotic regulator have failed.By contrast, several other hyperosmotically induced genes (otsBA, treA, osmB, osmY, and bolA) are under the control of s , a sigma subunit of RNA polymerase in E. coli that is encoded by the rpoS gene (13,14,19,34). This seems to implicate s as a global regulator in the osmotic control of gene expression. In fact, this would be a second global regulatory role for s , which is usually regarded as a stationary-phasespecific sigma factor since the genes mentioned above, as well as many other s -dependent genes, are induced during entry into stationary phase (for recent reviews, see references 11, 12, and 23). Besides being growth phase regulated at the levels of transcription, translation, and s protein stability, rpoS has a...

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Section: Discussionmentioning

confidence: 98%

Posttranscriptional osmotic regulation of the sigma(s) subunit of RNA polymerase in Escherichia coli

et al. 1996

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“…Regulation in response to osmolarity is mediated by the OmpR-binding sites, integration host factor, and the micF gene (47,48,55), while the response to temperature is mediated by the micF gene (4). Previous studies have proposed that under low-osmolarity lake water at ambient temperature, OmpF is the major porin expressed; in contrast, under high-osmolarity animal intestine at 37°C, OmpC is the predominant porin expressed (38,45).…”

Section: Discussionmentioning

confidence: 99%

Klebsiella pneumoniae Outer Membrane Porins OmpK35 and OmpK36 Play Roles in both Antimicrobial Resistance and Virulence

Tsai

Fung

Lin

et al. 2011

Antimicrob Agents Chemother

278

228

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OmpK35 and OmpK36 are the major outer membrane porins of Klebsiella pneumoniae. In this study, a virulent clinical isolate was selected to study the role of these two porins in antimicrobial resistance and virulence. The single deletion of ompK36 (⌬ompK36) resulted in MIC shifts of cefazolin, cephalothin, and cefoxitin from susceptible to resistant, while the single deletion of ompK35 (⌬ompK35) had no significant effect. A double deletion of ompK35 and ompK36 (⌬ompK35/36) further increased these MICs to high-level resistance and led to 8-and 16-fold increases in the MICs of meropenem and cefepime, respectively. In contrast to the routine testing medium, which is of high osmolarity, susceptibility tests using low-osmolarity medium showed that the ⌬ompK35 mutation resulted in a significant (>4-fold) increase in the MICs of cefazolin and ceftazidime, whereas a ⌬ompK36 deletion conferred a significantly (4-fold) lower increase in the MIC of cefazolin. In the virulence assays, a significant (P < 0.05) defect in the growth rate was found only in the ⌬ompK35/36 mutant, indicating the effect on metabolic fitness. A significant (P < 0.05) increase in susceptibility to neutrophil phagocytosis was observed in both ⌬ompK36 and ⌬ompK35/36 mutants. In a mouse peritonitis model, the ⌬ompK35 mutant showed no change in virulence, and the ⌬ompK36 mutant exhibited significantly (P < 0.01) lower virulence, whereas the ⌬ompK35/36 mutant presented the highest 50% lethal dose of these strains. In conclusion, porin deficiency in K. pneumoniae could increase antimicrobial resistance but decrease virulence at the same time.

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“…However, this is based on experiments with sucrose rather than NaCl and not in the presence of glycine betaine, which may interfere with porin stoichiometry (34,35) together with other factors, such as glucose availability (31). In addition, small RNAs are involved posttranscriptionally with the regulation of these porins under osmotic stress, so their gene expression would not exactly correlate with levels of mature protein (36).…”

Section: Figmentioning

confidence: 99%

Metabolic Shift of Escherichia coli under Salt Stress in the Presence of Glycine Betaine

Métris

George

Mulholland

et al. 2014

Appl Environ Microbiol

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An important area of food safety focuses on bacterial survival and growth in unfavorable environments. In order to understand how bacteria adapt to stresses other than nutrient limitation in batch cultures, we need to develop mechanistic models of intracellular regulation and metabolism under stress. We studied the growth of Escherichia coli in minimal medium with added salt and different osmoprotectants. To characterize the metabolic efficiency with a robust parameter, we identified the optical density (OD) values at the inflection points of measured "OD versus time" growth curves and described them as a function of glucose concentration. We found that the metabolic efficiency parameter did not necessarily follow the trend of decreasing specific growth rate as the salt concentration increased. In the absence of osmoprotectant, or in the presence of proline, the metabolic efficiency decreased with increasing NaCl concentration. However, in the presence of choline or glycine betaine, it increased between 2 and 4.5% NaCl before declining at 5% NaCl and above. Microarray analysis of the transcriptional network and proteomics analysis with glycine betaine in the medium indicated that between 4.5 and 5% NaCl, the metabolism switched from aerobic to fermentative pathways and that the response to osmotic stress is similar to that for oxidative stress. We conclude that, although the growth rate appeared to decrease smoothly with increasing NaCl, the metabolic strategy of cells changed abruptly at a threshold concentration of NaCl.

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micF antisense RNA has a major role in osmoregulation of OmpF in Escherichia coli

Cited by 50 publications

References 48 publications

Posttranscriptional osmotic regulation of the sigma(s) subunit of RNA polymerase in Escherichia coli

Posttranscriptional osmotic regulation of the sigma(s) subunit of RNA polymerase in Escherichia coli

Klebsiella pneumoniae Outer Membrane Porins OmpK35 and OmpK36 Play Roles in both Antimicrobial Resistance and Virulence

Metabolic Shift of Escherichia coli under Salt Stress in the Presence of Glycine Betaine

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