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Applied and Environmental Microbiology, September 2007, p. 5633-5638, Vol. 73, No. 17
0099-2240/07/$08.00+0     doi:10.1128/AEM.01049-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Acid Tolerance of Biofilm Cells of Streptococcus mutans{triangledown}

Jessica Welin-Neilands and Gunnel Svensäter*

Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden

Received 11 May 2007/ Accepted 4 July 2007

Streptococcus mutans, a member of the dental plaque community, has been shown to be involved in the carious process. Cells of S. mutans induce an acid tolerance response (ATR) when exposed to sublethal pH values that enhances their survival at a lower pH. Mature biofilm cells are more resistant to acid stress than planktonic cells. We were interested in studying the acid tolerance and ATR-inducing ability of newly adhered biofilm cells of S. mutans. All experiments were carried out using flow-cell systems, with acid tolerance tested by exposing 3-h biofilm cells to pH 3.0 for 2 h and counting the number of survivors by plating on blood agar. Acid adaptability experiments were conducted by exposing biofilm cells to pH 5.5 for 3 h and then lowering the pH to 3.5 for 30 min. The viability of the cells was assessed by staining the cells with LIVE/DEAD BacLight viability stain. Three-hour biofilm cells of three different strains of S. mutans were between 820- and 70,000-fold more acid tolerant than corresponding planktonic cells. These strains also induced an ATR that enhanced the viability at pH 3.5. The presence of fluoride (0.5 M) inhibited the induction of an ATR, with 77% fewer viable cells at pH 3.5 as a consequence. Our data suggest that adhesion to a surface is an important step in the development of acid tolerance in biofilm cells and that different strains of S. mutans possess different degrees of acid tolerance and ability to induce an ATR.

* Corresponding author. Mailing address: Department of Oral Biology, Faculty of Odontology, Malmö University, SE-205 06 Malmö, Sweden. Phone: 46 40 665 84 96. Fax: 46 40 925359. E-mail: gunnel.svensater{at}od.mah.se

{triangledown} Published ahead of print on 13 July 2007.

Applied and Environmental Microbiology, September 2007, p. 5633-5638, Vol. 73, No. 17
0099-2240/07/$08.00+0     doi:10.1128/AEM.01049-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Hojo, K., Nagaoka, S., Ohshima, T., Maeda, N. (2009). Bacterial Interactions in Dental Biofilm Development. JDR 88: 982-990 [Abstract] [Full Text]  


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