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Applied and Environmental Microbiology, February 2000, p. 659-663, Vol. 66, No. 2
Department of Biomedical Engineering,
University of Groningen, 9712 KZ Groningen, The Netherlands
Received 24 May 1999/Accepted 15 November 1999
The release of biosurfactants by adhering microorganisms as a
defense mechanism against other colonizing strains on the same substratum surface has been described previously for probiotic bacteria
in the urogenital tract, the intestines, and the oropharynx but not for
microorganisms in the oral cavity. Two Streptococcus mitis
strains (BA and BMS) released maximal amounts of biosurfactants when
they were grown in the presence of sucrose and were harvested in the
early stationary phase. The S. mitis biosurfactants reduced the surface tensions of aqueous solutions to about 30 to 40 mJ m
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Inhibition of Streptococcus mutans NS Adhesion to
Glass with and without a Salivary Conditioning Film by
Biosurfactant- Releasing Streptococcus mitis
Strains
2. Biochemical and physicochemical analyses revealed
that the biosurfactants released were glycolipids. An acid-precipitated
fraction was extremely surfactive and was identified as a
rhamnolipidlike compound. In a parallel-plate flow chamber, the number
of Streptococcus mutans NS cells adhering to glass with and
without a salivary conditioning film in the presence of
biosurfactant-releasing S. mitis BA and BMS (surface
coverage, 1 to 4%) was significantly reduced compared with the number
of S. mutans NS cells adhering to glass in the absence of
S. mitis. S. mutans NS adhesion in the presence of non-biosurfactant-releasing S. mitis BA and BMS was not
reduced at all. In addition, preadsorption of isolated S. mitis biosurfactants to glass drastically reduced the adhesion of
S. mutans NS cells and the strength of their bonds to
glass, as shown by the increased percentage of S. mutans NS
cells detached by the passage of air bubbles through the flow chamber.
Preadsorption of the acid-precipitated fraction inhibited S. mutans adhesion up to 80% in a dose-responsive manner. These
observations indicate that S. mitis plays a protective role
in the oral cavity and protects against colonization of saliva-coated surfaces by cariogenic S. mutans.
*
Corresponding author. Mailing address: Department of
Biomedical Engineering, University of Groningen, Bloemsingel 10, 9712 KZ Groningen, The Netherlands. Phone: 31-50-3633140. Fax:
31-50-3633159. E-mail:
H.J.Busscher{at}med.rug.nl.
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