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Microbiology. 2005 Jun;151(Pt 6):1823-37.

Up-regulation of competence- but not stress-responsive proteins accompanies an altered metabolic phenotype in Streptococcus mutans biofilms.

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Institute of Dental Research, Westmead Millennium Institute, Westmead Centre for Oral Health, PO Box 533, Wentworthville, NSW 2145, Australia.


Mature biofilm and planktonic cells of Streptococcus mutans cultured in a neutral pH environment were subjected to comparative proteome analysis. Of the 242 protein spots identified, 48 were significantly altered in their level of expression (P<0.050) or were unique to planktonic or biofilm-grown cells. Among these were four hypothetical proteins as well as proteins known to be associated with the maintenance of competence or found to possess a cin-box-like element upstream of their coding gene. Most notable among the non-responsive genes were those encoding the molecular chaperones DnaK, GroEL and GroES, which are considered to be up-regulated by sessile growth. Analysis of the rest of the proteome indicated that a number of cellular functions associated with carbon uptake and cell division were down-regulated. The data obtained were consistent with the hypothesis that a reduction in the general growth rate of mature biofilms of S. mutans in a neutral pH environment is associated with the maintenance of transformation without the concomitant stress response observed during the transient state of competence in bacterial batch cultures.

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