[Protein expression by planktonic and biofilm cells of clinical isolations of Streptococcus mutans].

OBJECTIVE

To investigate the changes in the surface-associated protein expression of planktonic cells and biofilm cells of clinical isolations of Streptococcus mutans (Sm).

METHODS

The proteins were extracted by the method of Homer from the nonadhered planktonic and the adhered biofilm cells and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis followed by image analysis. Proteins were identified by matrix-assisted laser desorption time of flight mass spectrometry and computer-assisted protein sequence analysis.

RESULTS

Image analysis revealed that 30% - 31% of the protein spots in biofilm was modulated. A total of 238 proteins changed 1.3-fold or greater in biofilm cells compared to planktonic cells in Sm18, with 5 only expressed in biofilm cells and 5 not expressed in biofilm cells. A total of 279 proteins changed 1.3-fold or greater in biofilm cells compared to planktonic cells in Sm593, with 12 only expressed in biofilm cells and 2 not expressed in biofilm cells. Two clinical isolations in biofilm cells had three identical protein expressions whose functions were associated with biosynthetic processes.

CONCLUSIONS

The two clinical isolations in biofilm status have high expression of some special proteins, which are presumed to be key proteins essential for formation of biofilm. The difference of protein expression in biofilm cells of the two clinical isolations may represent their distinct characters.