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  • 1.
    Neilands, Jessica
    et al.
    Malmö högskola, Odontologiska fakulteten (OD).
    Wilkins, Joanna C
    Beighton, David
    Wrzesinski, Krzysztof
    Fey, Stephen J
    Mose-Larsen, Peter
    Hamilton, Ian R
    Svensäter, Gunnel
    Malmö högskola, Odontologiska fakulteten (OD).
    Effect of acid shock on protein expression by biofilm cells of Streptococcus mutans2003Ingår i: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 227, nr 2, s. 287-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Streptococcus mutans is a component of the dental plaque biofilm and a major causal agent of dental caries. Log-phase cells of the organism are known to induce an acid tolerance response (ATR) at sub-lethal pH values ( approximately 5.5) that enhances survival at lower pH values such as those encountered in caries lesions. In this study, we have employed a rod biofilm chemostat system to demonstrate that, while planktonic cells induced a strong ATR at pH 5.5, biofilm cells were inherently more acid resistant than such cells in spite of a negli-gible induction of an ATR. Since these results suggested that surface growth itself triggered an ATR in biofilm cells, we were interested in comparing the effects of a pH change from 7.5 to 5.5 on protein syn-thesis by the two cell types. For this, cells were pulse labeled with [(14)C]-amino acids following the pH change to pH 5.5, the proteins extracted and separated by two-dimensional (2D) electrophoresis fol-lowed by autoradiography and computer-assisted image analysis. A comparison between the cells incubated at pH 5.5 and the control biofilm cells revealed 23 novel proteins that were absent in the control cells, and 126 proteins with an altered relative rate of synthesis. While the number of changes in protein expression in the biofilm cells was within the same range as for planktonic cells, the magnitude of their change was significantly less in biofilm cells, supporting the observa-tion that acidification of biofilm cells induced a negligible ATR. Mass spectrometry and computer-assisted protein sequence analysis revealed that ATR induction of the planktonic cells resulted in the downregula-tion of glycolytic enzymes presumably to limit cellular damage by the acidification of the external environment. On the other hand, the gly-colytic enzymes in control biofilm cells were significantly less down-regulated and key enzymes, such as lactate dehydrogenase were upregulated during pH 5.5 incubation, suggesting that the enhanced acid resistance of biofilm cells is associated with the maintenance of pH homeostasis by H+ extrusion via membrane ATPase and increased lactate efflux.

  • 2.
    Svensäter, Gunnel
    et al.
    Malmö högskola, Odontologiska fakulteten (OD). Malmö högskola, Biofilms Research Center for Biointerfaces.
    Welin, J
    Malmö högskola, Odontologiska fakulteten (OD).
    Wilkins, J C
    Department of Oral Microbiology, GKT Dental Institute, London, UK.
    Beighton, D
    Department of Oral Microbiology, GKT Dental Institute, London, UK.
    Hamilton, I R
    Department of Oral Biology, Faculty of Dentistry, University of Manitoba, Winnipeg, MB, Canada.
    Protein expression by planktonic and biofilm cells of Streptococcus mutans2001Ingår i: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 205, nr 1, s. 139-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Streptococcus mutans, a major causal agent of dental caries, functions in nature as a component of a biofilm on teeth (dental plaque) and yet very little information is available on the physiology of the organism in such surface-associated communities. As a consequence, we undertook to examine the synthesis of proteins by planktonic and biofilm cells growing in a biofilm chemostat at pH 7.5 at a dilution rate of 0.1 h(-1) (mean generation time=7 h). Cells were incubated with (14)C-labelled amino acids, the proteins extracted and separated by two-dimensional electrophoresis followed by autoradiography and computer-assisted image analysis. Of 694 proteins analysed, 57 proteins were enhanced 1.3-fold or greater in biofilm cells compared to planktonic cells with 13 only expressed in sessile cells. Diminished protein expression was observed with 78 proteins, nine of which were not expressed in biofilm cells. The identification of enhanced and diminished proteins by mass spectrometry and computer-assisted protein sequence analysis revealed that, in general, glycolytic enzymes involved in acid formation were repressed in biofilm cells, while biosynthetic processes were enhanced. The results show that biofilm cells possess novel proteins, of as yet unknown function, that are not present in planktonic cells.

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