Two-Dimensional Fluorescence Difference Gel Electrophoretic Analysis ofStreptococcusmutansBiofilms

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Abstract
Compared with traditional two-dimensional (2D) proteome analysis of Streptococcus mutans grown as a biofilm from a planktonic culture at steady state (Rathsam et al., Microbiol. 2005, 151, 1823−1837), the use of 2D fluorescence difference gel electrophoresis (DIGE) led to a 3-fold increase in the number of identified protein spots that were significantly altered in their level of expression (P < 0.050). Of the 73 identified proteins, only nine were up-regulated in biofilm grown cells. The results supported the previously surmised hypothesis that general metabolic functions were down-regulated in response to a reduction in growth rate in mature S. mutans biofilms. Up-regulation of competence proteins without any concomitant increase in stress-responsive proteins was confirmed, while the levels of glucosyltransferase C (GtfC), involved in glucan formation, O-acetylserine sulfhyrylase (cysteine synthetase A; CsyK), implicated in the formation of [Fe−S] clusters, and a hypothetical protein encoded by the open reading frame, SMu0188, were also up-regulated. Keywords: proteomics • two-dimensional fluorescence difference gel electrophoresis (DIGE) • Streptococcus mutans • biofilm • stress-responsive proteins • competence • quorum sensing • metabolism