Molecular characterization of a STreptococcus mutans mutant altered in environmental stress responses

Yamashita, Yoshihisa; Takehara, Tadamichi; Kuramitsu, Howard K.

doi:10.1128/jb.175.19.6220-6228.1993

Cited by 93 publications

(96 citation statements)

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“…Using Tn916 mutagenesis, Yamashita et al (1993) identified an acid-sensitive mutant of S . mutans GS.5 deficient in diacylglyerol kinase, an enzyme involved in phospholipid metabolism and, therefore, in maintenance of membrane architecture and composition.…”

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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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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“…For instance, a dgkA-null mutant of the oral pathogen S. mutans was more susceptible toward bacitracin than the parental strain, 65 suggesting that C 55 -OH phosphorylation constitutes a bypass of the biosynthetic or recycling pathway when the latter is inhibited. For less evident reasons, the latter mutant was also affected for growth at low pH, 122 the biosynthesis of certain lantibiotics, 18 the formation of biofilms, 124 as well as for virulence. 97 Likewise, DgkA from B. subtilis was shown to be required for sporulation by a mechanism that is yet to be clearly established.…”

Section: Formation and Role Of C 55 -P Derivativesmentioning

confidence: 99%

Deciphering the Metabolism of Undecaprenyl-Phosphate: The Bacterial Cell-Wall Unit Carrier at the Membrane Frontier

Manat

Roure

Auger

et al. 2014

Microbial Drug Resistance

121

139

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During the biogenesis of bacterial cell-wall polysaccharides, such as peptidoglycan, cytoplasmic synthesized precursors should be trafficked across the plasma membrane. This essential process requires a dedicated lipid, undecaprenyl-phosphate that is used as a glycan lipid carrier. The sugar is linked to the lipid carrier at the inner face of the membrane and is translocated toward the periplasm, where the glycan moiety is transferred to the growing polymer. Undecaprenyl-phosphate originates from the dephosphorylation of its precursor undecaprenyl-diphosphate, with itself generated by de novo synthesis or by recycling after the final glycan transfer. Undecaprenyl-diphosphate is de novo synthesized by the cytosolic cis-prenyltransferase undecaprenyldiphosphate synthase, which has been structurally and mechanistically characterized in great detail highlighting the condensation process. In contrast, the next step toward the formation of the lipid carrier, the dephosphorylation step, which has been overlooked for many years, has only started revealing surprising features. In contrast to the previous step, two unrelated families of integral membrane proteins exhibit undecaprenyldiphosphate phosphatase activity: BacA and members of the phosphatidic acid phosphatase type 2 super-family, raising the question of the significance of this multiplicity. Moreover, these enzymes establish an unexpected link between the synthesis of bacterial cell-wall polymers and other biological processes. In the present review, the current knowledge in the field of the bacterial lipid carrier, its mechanism of action, biogenesis, recycling, regulation, and future perspective works are presented.

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Section: Introductionmentioning

confidence: 99%

“…Insertion of transposon Tn916 within the codon of the tenth amino acid from the C terminus of the Dgk homologue causes defective growth of the resulting mutant GS5Tn1 at low pH (Yamashita et al, 1993). In addition, this mutant is sensitive to high osmolarity and elevated temperature (Yamashita et al, 1993). Chen et al (1998) reported that the S. mutans mutant T8-1 with a similar deletion of the Dgk homologue was defective in lantibiotic mutacin II production, which is related to an environmental stress response.…”

Section: Introductionmentioning

confidence: 99%

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Kinase activity of the dgk gene product is involved in the virulence of Streptococcus mutans

et al. 2009

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C-terminal deletion of the diacylglycerol kinase (Dgk) homologue of the cariogenic oral bacterium Streptococcus mutans resulted in loss of aciduricity. To confirm the role of the C terminus of the Dgk homologue in aciduricity, various mutants of S. mutans UA159 with a C-terminally truncated Dgk homologue were constructed. The deletion of one or two amino acid residues at the C terminus had no effect on the acid-tolerance properties of mutants. When further amino acid residues at the C terminus were removed, mutants became more acid-sensitive. The mutant with deletion of eight amino acid residues at the C terminus did not grow at pH 5.5, suggesting that the C-terminal tail of the Dgk homologue was indispensable for tolerance to acid stress in S. mutans. Kinase activity assays revealed that deletion of the C-terminal amino acids of Dgk led to a reduction of kinase activity for undecaprenol. A truncated mutant that had completely lost kinase activity was unable to grow at pH 5.5. These results suggest that the acid tolerance of S. mutans is closely related to kinase activity of the Dgk homologue. Additionally, the dgk deletion mutant exhibited markedly reduced levels of smooth-surface carious lesions in pathogen-free rats, despite there being no difference between the mutant and the parental organism in the extent of total smooth surface plaque. The results suggest that Dgk activity may play a direct role in the virulence of S. mutans.

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Molecular characterization of a STreptococcus mutans mutant altered in environmental stress responses

Cited by 93 publications

References 35 publications

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

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

Deciphering the Metabolism of Undecaprenyl-Phosphate: The Bacterial Cell-Wall Unit Carrier at the Membrane Frontier

Kinase activity of the dgk gene product is involved in the virulence of Streptococcus mutans

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