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Analysis of Small RNAs in Streptococcus mutans under Acid Stress—A New Insight for Caries Research

1,2, 1,2, 1,2, 1,2, 1,2, 1,2 and 1,2,*
Department of Preventive Dentistry, Guanghua School of Stomatology, Sun Yat-Sen University, 56 Ling Yuan Road West, Guangzhou 510055, China
Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-Sen University, Guangzhou 510055, China
Author to whom correspondence should be addressed.
Academic Editor: Patrick C. Y. Woo
Int. J. Mol. Sci. 2016, 17(9), 1529;
Received: 14 July 2016 / Revised: 6 September 2016 / Accepted: 7 September 2016 / Published: 14 September 2016
(This article belongs to the Section Biochemistry)
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Streptococcus mutans (S. mutans) is the major clinical pathogen responsible for dental caries. Its acid tolerance has been identified as a significant virulence factor for its survival and cariogenicity in acidic conditions. Small RNAs (sRNAs) are recognized as key regulators of virulence and stress adaptation. Here, we constructed three libraries of sRNAs with small size exposed to acidic conditions for the first time, followed by verification using qRT-PCR. The levels of two sRNAs and target genes predicted to be bioinformatically related to acid tolerance were further evaluated under different acid stress conditions (pH 7.5, 6.5, 5.5, and 4.5) at three time points (0.5, 1, and 2 h). Meanwhile, bacterial growth characteristics and vitality were assessed. We obtained 1879 sRNAs with read counts of at least 100. One hundred and ten sRNAs were perfectly mapped to reported msRNAs in S. mutans. Ten out of 18 sRNAs were validated by qRT-PCR. The survival of bacteria declined as the acid was increased from pH 7.5 to 4.5 at each time point. The bacteria can proliferate under each pH except pH 4.5 with time. The levels of sRNAs gradually decreased from pH 7.5 to 5.5, and slightly increased in pH 4.5; however, the expression levels of target mRNAs were up-regulated in acidic conditions than in pH 7.5. These results indicate that some sRNAs are specially induced at acid stress conditions, involving acid adaptation, and provide a new insight into exploring the complex acid tolerance for S. mutans. View Full-Text
Keywords: dental caries; gene expression; sRNAs; Streptococcus mutans; virulence dental caries; gene expression; sRNAs; Streptococcus mutans; virulence

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Liu, S.; Tao, Y.; Yu, L.; Zhuang, P.; Zhi, Q.; Zhou, Y.; Lin, H. Analysis of Small RNAs in Streptococcus mutans under Acid Stress—A New Insight for Caries Research. Int. J. Mol. Sci. 2016, 17, 1529.

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