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Protein expression by planktonic and biofilm cells of Streptococcus mutans
Malmö högskola, Faculty of Odontology (OD). Malmö högskola, Biofilms Research Center for Biointerfaces.ORCID iD: 0000-0003-3173-7577
Malmö högskola, Faculty of Odontology (OD).
Department of Oral Microbiology, GKT Dental Institute, London, UK.
Department of Oral Microbiology, GKT Dental Institute, London, UK.
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2001 (English)In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 205, no 1, p. 139-146Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2001. Vol. 205, no 1, p. 139-146
Keywords [en]
Animals, Bacterial Proteins, Biofilms, Culture Media, Dental Caries, Electrophoresis, Gel, Two-Dimensional, Humans, Image Processing, Computer-Assisted, Plankton, Streptococcus mutans
National Category
Dentistry
Identifiers
URN: urn:nbn:se:mau:diva-15570DOI: 10.1111/j.1574-6968.2001.tb10937.xISI: 000172471900021PubMedID: 11728728Local ID: 28589OAI: oai:DiVA.org:mau-15570DiVA, id: diva2:1419092
Available from: 2020-03-30 Created: 2020-03-30 Last updated: 2024-05-23Bibliographically approved
In thesis
1. Acid Tolerance of Streptococcus Mutans Biofilms
Open this publication in new window or tab >>Acid Tolerance of Streptococcus Mutans Biofilms
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

Mikrobiologisk forskning har till stor del bedrivits genom att man odlat bakterier i näringslösningar och på agarplattor och sedan studera bakterierna på olika sätt. Detta sätt att odla bakterier överensstämmer inte särskilt bra med hur bakterier växer i verkligenheten. I naturen växer bakterier fastsittande på olika typer av ytor (tandemalj, epitel, stenar, plastytor etc.) i s.k. biofilmer. Det har visat sig att bakterier i biofilmer inte alls beter sig som bakterier som växer fritt i en näringslösning (planktonisk form). Biofilmbak-terier skiljer sig från planktoniska bakterier genom att de är mer resistenta mot antibiotika och biocider. De är mer stresståliga, de växer långsammare och de har ett annorlunda gen- och proteinuttryck. Sammantaget har biofilmbakterier andra egenskaper. På grund av detta, har fokus inom mikrobiologisk forskning det senaste decenniet riktats mot att studera biofilmer för att komma närmare bakteriernas verklighet. I munnen växer bakterierna i biofilmer. Bakterierna i munnen är nödvändiga för att god munhälsa men de är också orsak till två av världens vanligaste sjukdomar; karies och parodontit. Streptococcus mutans tillhör den normala munfloran men medverkar också till att karies utvecklas. Karies uppstår när det blir en obalans i det orala ekosystemet. När man äter sjunker pH i munnen pga att bakterierna i plack producerar syror när de bryter ner kolhydrater. Om man äter ofta kommer pH i plack att vara surt under längre perioder, vilket leder till en selektion av bakterier som är stresståliga och kan anpassa sig till den sura miljön. Detta resulterar i att en syratolerant mikroflora dominerar i placket. Dessa bakterier har i sin tur kapacitet att göra det ännu surare i placket under långa perioder. Detta kan leda till demineralisering av emaljen och upp-komst av karies. S. mutans anpassar sig till en sur miljö genom att inducera en syratoleransrespons (ATR) vid subletala pH-värden. Syftet med denna avhandling var att studera hur S. mutans beter sig när den växer i biofilmer och ta reda på mer om syratoleransresponsen i S. mutans biofilmer. Resultaten från avhandlingen visar att S. mutans bakterier som vuxit i en biofilm i tre dagar har ett annorlunda proteinuttryck än planktoniska bakterier och att förändringar i proteinuttryck sker redan efter två timmar av ytkontakt. Proteinuttrycket ändras efter hand som biofilmen växer och blir äldre. Biofilmbakterierna visade sig också vara många gånger mer syratoleranta än de planktoniska bakterierna och ytkontakt i sig var viktigt för den ökade syratole-ransen. Äldre biofilmer (3 dagar) var mer syratoleranta än unga biofilmer (3 timmar) vilket kan bero på att de utsatts för pH chocker under växt i biofilmen och därmed inducerat en ATR. Unga biofilmer inducerade en ATR när de utsattes för pH 5.5 i tre timmar och denna ATR kunde inhiberas genom tillsats av fluor. Det visade sig också att olika stammar av S. mutans var olika syra-toleranta och hade olika förmåga att inducera en ATR. Detta kan i praktiken innebära att människor med bakterier som är mer benägna att inducera en ATR löper större risk att utveckla karies. Genom att förhindra induceringen av ATR skulle man alltså kunna förhindra utvecklingen av karies.

Abstract [en]

In nature, bacteria are organized in surface-associated biofilm communities. Dental plaque is one of the most studied biofilms and harbours many different species including the star of this thesis Streptococcus mutans. S. mutans has been implicated in the aetiology of caries and has been studied extensively but most research has been carried out on liquid cultures (planktonic cells). Biofilm cells have been shown to differ in many ways from planktonic cells when it comes to protein and gene expression, growth rate, and stress tolerance. The overall aim of this thesis was to study S. mutans grown in biofilms of different ages (2 hours – 3 days) and to study the acid tolerance response (ATR) in biofilm cells. Biofilms were grown in chemostats, on glass slides and in flow-cell systems. To evaluate protein expression in cells, 14C-labelled proteins were separated by 2-dimensional gel eletrophoresis (2-DE) followed by autoradiography and computer-assisted image analysis. Acid killing experiments were conducted by exposing the cells to pH 3.0 for two hours and then counting the number of survivors by plating on blood agar. ATR-experiments were carried out in a similar way to the acid killing experiments except that the cells were first exposed to pH 5.5 for 2-3 hours and then exposed to pH 3.0-3.5 for 30 minutes to two hours. Surviving cells were counted by plating on blood agar but also examined using LIVE/DEAD® BacLightTM viability stain. Inhibition of the cell’s ability to induce an ATR was tested by exposing the cells to 0.5 M fluoride. Mature biofilm cells (3 days old) showed a different protein expression pattern compared to corresponding planktonic cells with the most prominent difference being the decreased expression of enzymes involved in carbohydrate catabolism. Contact with a surface induced changes in protein expression as quickly as two hours after surface adhesion. In these cells however, the proteins involved in carbohydrate catabolism were enhanced. Surface contact and growth in a biofilm lead to increased acid tolerance. In newly formed biofilm cells of S. mutans H7, 5% of the cells survived an acid shock of pH 3.0 for two hours compared to only 0.0004% of the planktonic cells. The mature biofilm cells were even more acid tolerant with 41.5% survivors after two hours at pH 3.0. Mature biofilms induced only a negligible ATR that did not enhance their survival significantly. Still, 20% of the proteins analysed had an altered expression after exposure to pH 5.5. In newly formed biofilm cells the ATR lead to decreased membrane damage at low pH as visualised by LIVE/DEAD® BacLightTM staining. Different strains showed different abilities to induce an ATR and it was also shown that this ATR could be inhibited by exposure to 0.5 M fluo-ride during the pH 5.5-adaptation period. The results of the thesis show that biofilm cells of S. mutans differ from their planktonic counterparts and the strains of S. mutans tested behave somewhat differently.

Place, publisher, year, edition, pages
Malmö University, 2007
Keywords
Acid tolerance, Streptococcus mutans, Biofilms, Acid stress, Fluoride
National Category
Dentistry
Identifiers
urn:nbn:se:mau:diva-7704 (URN)4702 (Local ID)91-7104-295-4 (ISBN)4702 (Archive number)4702 (OAI)
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Note: The papers are not included in the fulltext online

Available from: 2020-02-28 Created: 2020-02-28 Last updated: 2024-02-29Bibliographically approved

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