Document Detail

Global transcriptional analysis of acid-inducible genes in Streptococcus mutans: multiple two-component systems involved in acid adaptation.
MedLine Citation:
PMID:  19608608     Owner:  NLM     Status:  In-Process    
Streptococcus mutans in dental biofilms is regularly exposed to cycles of acidic pH during the ingestion of fermentable dietary carbohydrates. The ability of S. mutans to tolerate low pH is crucial for its virulence and pathogenesis in dental caries. To better understand its acid tolerance mechanisms, we performed genome-wide transcriptional analysis of S. mutans in response to an acidic pH signal. The preliminary results showed that adaptation of S. mutans to pH 5.5 induced differential expression of nearly 14 % of the genes in the genome, including 169 upregulated genes and 108 downregulated genes, largely categorized into nine functional groups. One of the most interesting findings was that the genes encoding multiple two-component systems (TCSs), including CiaHR, LevSR, LiaSR, ScnKR, Hk/Rr1037/1038 and ComDE, were upregulated during acid adaptation. Real-time qRT-PCR confirmed the same trend in the expression profiles of these genes at pH 5.5. To determine the roles of these transduction systems in acid adaptation, mutants with a deletion of the histidine-kinase-encoding genes were constructed and assayed for the acid tolerance response (ATR). The results revealed that inactivation of each of these systems resulted in a mutant that was impaired in ATR, since pre-exposure of these mutants to pH 5.5 did not induce the same level of protection against lethal pH levels as the parent did. A competitive fitness assay showed that all the mutants were unable to compete with the parent strain for persistence in dual-strain mixed cultures at acidic pH, although, with the exception of the mutant in liaS, little effect was observed at neutral pH. The evidence from this study suggests that the multiple TCSs are required for S. mutans to orchestrate its signal transduction networks for optimal adaptation to acidic pH.
Yongxing Gong; Xiao-Lin Tian; Tara Sutherland; Gary Sisson; Junni Mai; Junqi Ling; Yung-Hua Li
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-07-16
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  155     ISSN:  1350-0872     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2009 Oct 
Date Detail:
Created Date:  2009-09-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  England    
Other Details:
Languages:  eng     Pagination:  3322-32     Citation Subset:  IM    
Department of Applied Oral Sciences, Dalhousie University, Halifax, Canada.
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Grant Support
//Canadian Institutes of Health Research

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