Role of the citrate pathway in glutamate biosynthesis by Streptococcus mutans

Cvitkovitch, Dennis G.; Gutierrez, Juan A.; Bleiweis, Arnold S.

doi:10.1128/jb.179.3.650-655.1997

Cited by 50 publications

(51 citation statements)

References 34 publications

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“…Glutamate is metabolized within the cell through the urea and citrate cycles to phospho-enol-pyruvate, which enters the glycolytic pathway and can be metabolized to form organic acid end products (11). Therefore, we expected a possible connection between glutamate transport and proton extrusion.…”

Section: Resultsmentioning

confidence: 99%

Characterization of a Glutamate Transporter Operon, glnQHMP , in Streptococcus mutans and Its Role in Acid Tolerance

et al. 2010

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Glutamate contributes to the acid tolerance response (ATR) of many Gram-negative and Gram-positive bacteria, but its role in the ATR of the oral bacterium Streptococcus mutans is unknown. This study describes the discovery and characterization of a glutamate transporter operon designated glnQHMP (Smu.1519 to Smu.1522) and investigates its potential role in acid tolerance. Deletion of glnQHMP resulted in a 95% reduction in transport of radiolabeled glutamate compared to the wild-type UA159 strain. The addition of glutamate to metabolizing UA159 cells resulted in an increased production of acidic end products, whereas the glnQHMP mutant produced less lactic acid than UA159, suggesting a link between glutamate metabolism and acid production and possible acid tolerance. To investigate this possibility, we conducted a microarray analysis with glutamate and under pH 5.5 and pH 7.5 conditions which showed that expression of the glnQHMP operon was downregulated by both glutamate and mild acid. We also measured the growth kinetics of UA159 and its glnQHMP-negative derivative at pH 5.5 and found that the mutant doubled at a much slower rate than the parent strain but survived at pH 3.5 significantly better than the wild type. Taken together, these findings support the involvement of the glutamate transporter operon glnQHMP in the acid tolerance response in S. mutans.

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Section: Resultsmentioning

confidence: 99%

Characterization of a Glutamate Transporter Operon, glnQHMP , in Streptococcus mutans and Its Role in Acid Tolerance

et al. 2010

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“…The total iron contents in S. mutans (from 0.005 to 0.008% in dry weight) were some 2.5-to 4-fold less than that in E. coli grown in rich medium (1). Although the iron requirement in S. mutans reportedly depends on growth conditions (20), iron assimilation could facilitate metabolism, e.g., for amino acid biosynthesis utilizing the iron-containing protein aconitase (9) or potentially for activating iron-requiring ribonucleotide reductases identified in the genome sequence (2).…”

Section: Resultsmentioning

confidence: 99%

Regulation of the Intracellular Free Iron Pool by Dpr Provides Oxygen Tolerance to Streptococcus mutans

Yamamoto¹,

Fukui

Koujin³

et al. 2004

J Bacteriol

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). Here, we examined the intracellular free iron status of wild-type (WT) and dpr mutant strains of S. mutans, before and after exposure to air, by using electron spin resonance spectrometry. Under anaerobic conditions, free iron ion concentrations of WT and dpr strains were 225.9 ؎ 2.6 and 333.0 ؎ 61.3 M, respectively. Exposure of WT cells to air for 1 h induced Dpr expression and reduced intracellular free iron ion concentrations to 22.5 ؎ 5.3 M; under these conditions, dpr mutant cells maintained intracellular iron concentration at 230.3 ؎ 28.8 M. A decrease in cell viability and genomic DNA degradation was observed in the dpr mutant exposed to air. These data indicate that regulation of the intracellular free iron pool by Dpr is required for oxygen tolerance in S. mutans.

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“…Further, we present data here that suggest a role for Ffh in acidurance in S. mutans. (Hillman et al, 1987)], AS17 (sat-1 : : Tn917; Gutierrez et af., 1996) and AX1 (icd-1: : Tn917; Cvitkovitch et al, 1997) were grown in the following liquid and solid (2*0°/0 agar) media: Blood agar; Todd-Hewitt containing 0 3 % yeast extract (THYE) at pH 4.7-7.5, with the pH adjusted by addition of NaOH or HC1; tryptone yeast extract medium, containing 1 '/o tryptone, 0.5 '/O yeast extract, 0.1-1*0% (w/v) glucose (TYEG), galactose, lactose, sorbitol, mannitol or sucrose. Medium consisting of 2 '/O tryptose, 0.5 YO yeast extract, 0.5 O/ O NaCl, 0.1 YO Na,HPO,, 0.002 YO bromocresol purple and 1.0 YO of the above-mentioned sugars was used to study fermentation of carbon sources (TYEBP).…”

Section: Introductionmentioning

confidence: 99%

Streptococcus mutans ffh, a gene encoding a homologue of the 54 kDa subunit of the signal recognition particle, is involved in resistance to acid stress

et al. 1999

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The ability of Streptococcus mutans, a bacterial pathogen associated with dental caries, t o tolerate rapid drops in plaque pH (acidurance), is considered an important virulence factor. To study this trait, Tn917 mutants of 5. mutans strain JH1005 which display acid sensitivity have been isolated and partially characterized. In this paper, the characterization of one of these mutants, AS1 7, is reported. Preliminary sequence analysis revealed that the transposon insertion in AS17 occurred in the intergenic region of a two-gene locus which has been named sat for secretion and acid tolerance. This locus displays a high degree of homology t o the y/xM-ffh operon of Bacillus subtik The sat+ locus was cloned by complementation of a conditional Escherichia coli ffh mutant with an 5. mutans genomic library. Sequencing of the complementing clone identified the intact yIxM and #%i genes as well as a partial ORF with homology t o the proU/opuAC gene of B. subtilis which encodes the binding protein of the ProU/OpuA osmoregulated glycine betaine transport system. RNA dot blot experiments indicated steady-state levels of ffh mRNA in the mutant that were approximately eightfold lower compared to parental levels. This suggests a partial polar effect of the sat=l::Tn917 mutation on ffh expression. Upon acid shock (pH 5)# wild-type ffh mRNA levels were found t o increase approximately four-to eightfold compared to unstressed (pH 7.5) levels. Mutant levels remained unaltered under the same conditions. Experiments designed to investigate the origins of the acid-sensitivity of the mutant revealed a lack of an acid-adaptiveholerance response. Assays of proton-extruding ATPase (H+/ATPase) specific activity measured with purified membranes derived from acidAshocked AS17 showed twofold lower levels compared to the parent strain. Also, AS17 was found to be unable t o ferment sorbitol although it was able t o grow in glucose and a variety of other sugar substrates. These findings suggest that Ffh may be involved in the maintenance of a functional membrane protein composition during adaptation of S. mutans t o changing environmental conditions. Abbreviations: ATR, acid tolerance response; GSP, general secretory pathway; SRP, signal recognition particle. KeywordsThe CenBank accession number for the DNA sequence of the 3 kb DNA fragment containing the y/xM-ffh genes is U88582. INTRODUCTIONStreptococcus mutans plays a major role in the aetiology of human dental caries. This bacterium is able to demineralize dental enamel by generation of a localized acidic environment in plaque by rapid glycolysis of dietary sugars to lactic acid. In addition to its acidogenicity, S. mutans is able to tolerate exposure to continual and rapid cycles of acid shock. In vivo pH measurements have demonstrated that the pH of plaque can drop from pH 7.0 to values ranging from 3.0 to 4.0 in less than 20 min following the intake of carbohydrates (Imfeld & Lutz, 1980;Yamada et al., 1980;Mormann & Muhlemann, 1981 ; Schachtele & Harlander, 1984;Jensen & Wefel, 1989). E...

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Role of the citrate pathway in glutamate biosynthesis by Streptococcus mutans

Cited by 50 publications

References 34 publications

Characterization of a Glutamate Transporter Operon, glnQHMP , in Streptococcus mutans and Its Role in Acid Tolerance

Characterization of a Glutamate Transporter Operon, glnQHMP , in Streptococcus mutans and Its Role in Acid Tolerance

Regulation of the Intracellular Free Iron Pool by Dpr Provides Oxygen Tolerance to Streptococcus mutans

Streptococcus mutans ffh, a gene encoding a homologue of the 54 kDa subunit of the signal recognition particle, is involved in resistance to acid stress

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