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  • 1. Conlon, Brian
    et al.
    Geoghegan, Joan
    Waters, Elaine
    McCarthy, Hannah
    Rowe, S
    Davies, Julia R
    Malmö högskola, Faculty of Odontology (OD).
    Schaeffer, Carolyn
    Foster, Timothy
    Fey, Paula
    O'Gara, James P
    Role for the A Domain of Unprocessed Accumulation-Associated Protein (Aap) in the Attachment Phase of the Staphylococcus epidermidis Biofilm Phenotype2014In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 196, no 24, p. 4268-4275Article in journal (Refereed)
    Abstract [en]

    The polysaccharide intercellular adhesin or the cell wall-anchored accumulation-associated protein (Aap) mediates cellular accumulation during Staphylococcus epidermidis biofilm maturation. Mutation of sortase, which anchors up to 11 proteins (including Aap) to the cell wall, blocked biofilm development by the cerebrospinal fluid isolate CSF41498. Aap was implicated in this phenotype when Western blots and two-dimensional (2D) electrophoresis revealed increased levels of the protein in culture supernatants. Unexpectedly, reduced levels of primary attachment were associated with impaired biofilm formation by CSF41498 srtA and aap mutants. In contrast to previous studies, which implicated Aap proteolytic cleavage and, specifically, the Aap B domains in biofilm accumulation, the CSF41498 Aap protein was unprocessed. Furthermore, aap appeared to play a less important role in the biofilm phenotype of S. epidermidis 1457, in which the Aap protein is processed. Anti-Aap A-domain IgG inhibited primary attachment and biofilm formation in strain CSF41498 but not in strain 1457. The nucleotide sequences of the aap gene A-domain region and cleavage site in strains CSF41498 and 1457 were identical, implicating altered protease activity in the differential Aap processing results in the two strains. These data reveal a new role for the A domain of unprocessed Aap in the attachment phase of biofilm formation and suggest that extracellular protease activity can influence whether Aap contributes to the attachment or accumulation phases of the S. epidermidis biofilm phenotype

  • 2.
    Lima, Bruno P.
    et al.
    Univ Minnesota, Sch Dent, Dept Diagnost & Biol Sci, Minneapolis, MN 55455 USA..
    Davies, Julia R
    Malmö University, Faculty of Odontology (OD).
    Wickström, Claes
    Malmö University, Faculty of Odontology (OD).
    Johnstone, Karen F.
    Univ Minnesota, Sch Dent, Dept Diagnost & Biol Sci, Minneapolis, MN 55455 USA..
    Hall, Jeffrey W.
    Univ Minnesota, Sch Dent, Dept Diagnost & Biol Sci, Minneapolis, MN 55455 USA..
    Svensäter, Gunnel
    Malmö University, Faculty of Odontology (OD).
    Herzberg, Mark C.
    Univ Minnesota, Sch Dent, Dept Diagnost & Biol Sci, Minneapolis, MN 55455 USA..
    Streptococcus gordonii Poised for Glycan Feeding through a MUC5B-Discriminating, Lipoteichoic Acid-Mediated Outside-In Signaling Circuit2022In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 204, no 6, article id e00118-22Article in journal (Refereed)
    Abstract [en]

    Many oral bacteria employ cell wall-anchored adhesins to bind to the salivary films coating the teeth and mucosal surfaces. Surface binding prevents clearance and facilitates catabolism of salivary film glycoproteins. We asked whether Streptococcus gordonii adhesin expression changes in response to surface salivary cues using a eukaryote-like, outside-in recognition and signaling circuit. To determine whether the cues were discriminated, S. gordonii was tested during cell adhesion and biofilm formation on a MUC5B-rich or lower-molecular-mass salivary fraction or an uncoated abiotic surface. Cells were recovered and analyzed for differences in gene expression and proteins in cell wall fractions. In salivary-free conditions, planktonic S. gordonii presented three prominent cell wall LPXTG-motif proteins, SGO_1487, SGO_0890, and MbpA (mucin-binding protein A; SGO_0707). During biofilm formation on MUC5B-coated surfaces, MbpA, a MUC5B-binding protein, and key genes in the tagatose and quorum-sensing pathways were strongly promoted. The response to MUC5B required the two-component system (TCS), streptococcal regulator of adhesins sensor and regulator (SraSR, SGO_1180/81), lipoteichoic acid (LTA), and the homologous paired adhesins, SspA and SspB (SspAB). LTA appears to link the outside signal (MUC5B) to intramembrane SraSR. Tagatose pathway gene expression may poise cells to metabolize MUC5B glycans and, with a quorum-sensing gene (luxS), may direct formation of a consortium to facilitate glycan cross-feeding by S. gordonii. We now show that a Gram-positive bacterium discriminates specific surface environmental cues using an outside-in signaling mechanism to apparently optimize colonization of saliva-coated surfaces. IMPORTANCE All organisms throughout the tree of life sense and respond to their surface environments. To discriminate among mucosal surface environmental cues, we report that Streptococcus gordonii recognizes a high-molecular-weight mucin glycoprotein, MUC5B, using the paired adhesins SspAB and lipoteichoic acid; the latter bridges the outside signal to an intramembrane two-component system to transcriptionally regulate a MUC5B-specific adhesin and genes that may facilitate glycan catabolism. All organisms throughout the tree of life sense and respond to their surface environments. To discriminate among mucosal surface environmental cues, we report that Streptococcus gordonii recognizes a high-molecular-weight mucin glycoprotein, MUC5B, using the paired adhesins SspAB and lipoteichoic acid; the latter bridges the outside signal to an intramembrane two-component system to transcriptionally regulate a MUC5B-specific adhesin and genes that may facilitate glycan catabolism.

  • 3. Senadheera, Dilani B
    et al.
    Cordova, Martha
    Ayala, Eduardo A
    Chávez de Paz, L. E.
    Malmö högskola, Faculty of Odontology (OD).
    Singh, Kalpana
    Downey, Jennifer S
    Svensäter, Gunnel
    Malmö högskola, Faculty of Odontology (OD).
    Goodman, Steven D
    Cvitcovitch, Dennis
    Regulation of bacteriocin production and cell death by the VicRK signaling system in Streptococcus mutans2012In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 194, no 6, p. 1307-1316Article in journal (Refereed)
    Abstract [en]

    The VicRK two-component signaling system modulates biofilm formation, genetic competence, and stress tolerance in Streptococcus mutans. We show here that the VicRK modulates bacteriocin production and cell viability, in part by direct modulation of competence-stimulating peptide (CSP) production in S. mutans. Global transcriptome and real-time transcriptional analysis of the VicK-deficient mutant (SmuvicK) revealed significant modulation of several bacteriocin-related loci, including nlmAB, nlmC, and nlmD (P < 0.001), suggesting a role for the VicRK in producing mutacins IV, V, and VI. Bacteriocin overlay assays revealed an altered ability of the vic mutants to kill related species. Since a well-conserved VicR binding site (TGTWAH-N(5)-TGTWAH) was identified within the comC coding region, we confirmed VicR binding to this sequence using DNA footprinting. Overexpression of the vic operon caused growth-phase-dependent repression of comC, comDE, and comX. In the vic mutants, transcription of nlmC/cipB encoding mutacin V, previously linked to CSP-dependent cell lysis, as well as expression of its putative immunity factor encoded by immB, were significantly affected relative to the wild type (P < 0.05). In contrast to previous reports that proposed a hyper-resistant phenotype for the VicK mutant in cell viability, the release of extracellular genomic DNA was significantly enhanced in SmuvicK (P < 0.05), likely as a result of increased autolysis compared with the parent. The drastic influence of VicRK on cell viability was also demonstrated using vic mutant biofilms. Taken together, we have identified a novel regulatory link between the VicRK and ComDE systems to modulate bacteriocin production and cell viability of S. mutans.

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