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FEMS Microbiol Lett

Title:		ComX activity of Streptococcus mutans growing in biofilms
Author(s):		Aspiras MB; Ellen RP; Cvitkovitch DG;
Address:		"Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, Ont., Canada M5G 1G6"
Journal Title:		FEMS Microbiol Lett
Year:		2004
Volume:		238
Issue:		1
Page Number:		167 - 174
DOI:		10.1016/j.femsle.2004.07.032
ISSN/ISBN:		0378-1097 (Print) 0378-1097 (Linking)
Abstract:		"In many streptococci, including Streptococcus mutans, genetic competence is regulated by a quorum sensing system mediated by a competence stimulating peptide (CSP) pheromone, encoded by the comC gene. In Streptococcus pneumoniae, a central component of this system is ComX, which acts as an alternative sigma factor to activate competence genes involved in DNA uptake and processing. The quorum sensing system responsible for genetic competence induction in S. mutans has been linked to biofilm formation and the acid tolerance response. To examine the response of comX to CSP in S. mutans, a transcriptional fusion of the comX promoter (pcomX) with lacZ was constructed to generate reporter vector pcomx::pALH122 (replicative vector) and transformed into S. mutans UA159 comC-, which is unable to produce endogenous CSP. CSP was added and pcomX::lacZ relative expression index (REI) examined, revealing a 2-fold increase in maximal beta-gal activity 5 and 10 min after CSP addition. The effect of endogenous CSP on pcomX::lacZ expression was also examined by measuring REI in cells grown as a biofilm; peak pcomX activity was observed at 3 h. To determine the temporal pattern of transformation frequency, pMA2, a Spr shuttle vector, was transformed into biofilm-grown cells, with maximal transformation frequency observed at 3 h. Confocal microscopy was performed to examine pcomX activity using a similarly constructed green fluorescent protein reporter vector, pcomX::gfp, in a 4-h biofilm, revealing active pcomX activity in high cell density areas within the biofilm population. These results demonstrated a positive correlation between pcomX activity, natural transformation and competence development in biofilms"
Keywords:		"Adaptation, Physiological Artificial Gene Fusion Bacterial Proteins/*genetics/*metabolism Biofilms/*growth & development *Gene Expression Regulation, Bacterial Genes, Reporter Microscopy, Confocal Plasmids Promoter Regions, Genetic Streptococcus mutans/ge;"
Notes:		"MedlineAspiras, Marcelo B Ellen, Richard P Cvitkovitch, Dennis G eng R01 DE013230/DE/NIDCR NIH HHS/ R01DE013230-03/DE/NIDCR NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. England 2004/09/01 FEMS Microbiol Lett. 2004 Sep 1; 238(1):167-74. doi: 10.1016/j.femsle.2004.07.032"