HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplementary data All Versions of this Article: mic.0.031591-0v1 155/10/3322    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Gong, Y. Articles by Li, Y.-H. PubMed PubMed Citation Articles by Gong, Y. Articles by Li, Y.-H. Agricola Articles by Gong, Y. Articles by Li, Y.-H.

Global transcriptional analysis of acid-inducible genes in Streptococcus mutans: multiple two-component systems involved in acid adaptation

Yongxing Gong^1,

Xiao-Lin Tian^1,

¹ Department of Applied Oral Sciences, Dalhousie University, Halifax, Canada
² Department of Microbiology and Immunology, Dalhousie University, Halifax, Canada
³ Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, PR China

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.

Correspondence
Yung-Hua Li
yung-hua.li{at}dal.ca

These authors contributed equally to this work.

The NCBI GEO (www.ncbi.nlm.nih.gov/geo) accession number for the microarray data reported in this paper is GSE15125.

A figure describing the strategy for construction and confirmation of gene deletion mutants by PCR ligation mutagenesis, and tables of primers used for qRT-PCR and construction of the mutants in this study, and of genes differentially expressed in S. mutans during acid adaptation are available with the online version of this paper.