L-glutamine provides acid resistance for Escherichia coli through enzymatic release of ammonia

Lu, Pinyan; Ma, Dan; Chen, Yuling; Guo, Yingying; Chen, Guoqiang; Deng, Haiteng; Shi, Yigong

doi:10.1038/cr.2013.13

Cited by 195 publications

(216 citation statements)

References 29 publications

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“…After acid exposure, the intracellular pH decreases, and DNA is damaged. The cells can resist the acid stress through a variety of defence mechanisms, such as regulating the flow of protons inside and outside cells [11,13] and neutralizing intracellular protons through producing alkaline compounds [40]. Further, the DNA repair enzyme system can also assist cells to resist acid stress through repair of the damaged DNA [12].…”

Section: Discussionmentioning

confidence: 99%

Acid-resistant genes of oral plaque microbiome from the functional metagenomics

Zhang

Zheng

et al. 2018

Journal of Oral Microbiology

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Acid resistance is one of key properties assisting the survival of cariogenic bacteria in a dental caries environment, but only a few genes conferring acid resistance have been identified to data. Functional metagenomics provides a systematic method for investigating commensal DNA to identify genes that encode target functions. Here, the host strain Escherichia coli DH10B and a constructed bidirectional transcription vector pSKII+-lacZ contributed to the construction of a metagenomic library, and 46.6 Mb of metagenomic DNA was cloned from carious supragingival plaque of 8children along with screening for lethal functionality. The screen identified 2 positive clones that exhibited a similar aciduric phenotype to that of the positive controls. Bioinformatic analysis revealed that these two genes encoded an ATP/GTP-binding protein and a malate dehydrogenase. Moreover, we also performed functional screening of Streptococcus mutans, since it is one of the predominant cariogenic strains but was not identified in our initial screening. Five positive clones were retrieved. In conclusion, our improved functional metagenomics screening method helped in the identification of important acid resistance genes, thereby providing new insights into the mechanism underlying caries formation as well as in the prevention and treatment of early childhood caries (ECC).

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Section: Discussionmentioning

confidence: 99%

Acid-resistant genes of oral plaque microbiome from the functional metagenomics

Zhang

Zheng

et al. 2018

Journal of Oral Microbiology

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“…It is possible that the catabolic glycine decarboxylase pathway similarly serves to buffer the cytoplasm via the release of ammonia during glycine decarboxylation. Indeed, Lu et al recently demonstrated that the conversion of glutamine to glutamate, with the release of ammonia, can serve a protective role for E. coli during exposure at pH 2.5 (59).…”

Section: Figmentioning

confidence: 99%

Acid-Adapted Strains of Escherichia coli K-12 Obtained by Experimental Evolution

Harden

Creamer

et al. 2015

Appl Environ Microbiol

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Enteric bacteria encounter a wide range of pHs throughout the human intestinal tract. We conducted experimental evolution of Escherichia coli K-12 to isolate clones with increased fitness during growth under acidic conditions (pH 4.5 to 4.8). Twenty-four independent populations of E. coli K-12 W3110 were evolved in LBK medium (10 g/liter tryptone, 5 g/liter yeast extract, 7.45 g/liter KCl) buffered with homopiperazine-N,N=-bis-2-(ethanosulfonic acid) and malate at pH 4.8. At generation 730, the pH was decreased to 4.6 with HCl. By 2,000 generations, all populations had achieved higher endpoint growth than the ancestor at pH 4.6 but not at pH 7.0. All evolving populations showed a progressive loss of activity of lysine decarboxylase (CadA), a major acid stress enzyme. This finding suggests a surprising association between acid adaptation and moderation of an acid stress response. At generation 2,000, eight clones were isolated from four populations, and their genomes were sequenced. Each clone showed between three and eight missense mutations, including one in a subunit of the RNA polymerase holoenzyme (rpoB, rpoC, or rpoD). Missense mutations were found in adiY, the activator of the acid-inducible arginine decarboxylase (adiA), and in gcvP (glycine decarboxylase), a possible acid stress component. For tests of fitness relative to that of the ancestor, lacZ::kan was transduced into each strain. All acid-evolved clones showed a high fitness advantage at pH 4.6. With the cytoplasmic pH depressed by benzoate (at external pH 6.5), acid-evolved clones showed decreased fitness; thus, there was no adaptation to cytoplasmic pH depression. At pH 9.0, acid-evolved clones showed no fitness advantage. Thus, our acid-evolved clones showed a fitness increase specific to low external pH.

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“…Strains were cultured overnight in LB medium (10 g/liter tryptone, 5 g/liter yeast extract, 100 mM NaCl) buffered with 100 mM MES, pH 5.5. Glutamine (10 mM), which the bacteria convert to glutamate, the substrate of glutamate decarboxylase (86), was included. For anaerobic culture, closed 9-ml screw-cap tubes nearly full of medium were incubated for 18 h at 37°C.…”

Section: Figmentioning

confidence: 99%

Benzoate- and Salicylate-Tolerant Strains of Escherichia coli K-12 Lose Antibiotic Resistance during Laboratory Evolution

Creamer

Ditmars

Basting

et al. 2017

Appl Environ Microbiol

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Escherichia coli K-12 W3110 grows in the presence of membrane-permeant organic acids that can depress cytoplasmic pH and accumulate in the cytoplasm. We conducted experimental evolution by daily diluting cultures in increasing concentrations of benzoic acid (up to 20 mM) buffered at external pH 6.5, a pH at which permeant acids concentrate in the cytoplasm. By 2,000 generations, clones isolated from evolving populations showed increasing tolerance to benzoate but were sensitive to chloramphenicol and tetracycline. Sixteen clones grew to stationary phase in 20 mM benzoate, whereas the ancestral strain W3110 peaked and declined. Similar growth occurred in 10 mM salicylate. Benzoate-evolved strains grew like W3110 in the absence of benzoate, in media buffered at pH 4.8, pH 7.0, or pH 9.0, or in 20 mM acetate or sorbate at pH 6.5. Genomes of 16 strains revealed over 100 mutations, including single-nucleotide polymorphisms (SNPs), large deletions, and insertion knockouts. Most strains acquired deletions in the benzoate-induced multiple antibiotic resistance (Mar) regulon or in associated regulators such as rob and cpxA, as well as the multidrug resistance (MDR) efflux pumps emrA, emrY, and mdtA. Strains also lost or downregulated the Gad acid fitness regulon. In 5 mM benzoate or in 2 mM salicylate (2-hydroxybenzoate), most strains showed increased sensitivity to the antibiotics chloramphenicol and tetracycline; some strains were more sensitive than a marA knockout strain. Thus, our benzoate-evolved strains may reveal additional unknown drug resistance components. Benzoate or salicylate selection pressure may cause general loss of MDR genes and regulators. IMPORTANCE Benzoate is a common food preservative, and salicylate is the primary active metabolite of aspirin. In the gut microbiome, genetic adaptation to salicylate may involve loss or downregulation of inducible multidrug resistance systems. This discovery implies that aspirin therapy may modulate the human gut microbiome to favor salicylate tolerance at the expense of drug resistance. Similar aspirin-associated loss of drug resistance might occur in bacterial pathogens found in arterial plaques.

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L-glutamine provides acid resistance for Escherichia coli through enzymatic release of ammonia

Cited by 195 publications

References 29 publications

Acid-resistant genes of oral plaque microbiome from the functional metagenomics

Acid-resistant genes of oral plaque microbiome from the functional metagenomics

Acid-Adapted Strains of Escherichia coli K-12 Obtained by Experimental Evolution

Benzoate- and Salicylate-Tolerant Strains of Escherichia coli K-12 Lose Antibiotic Resistance during Laboratory Evolution

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