Effect of Different Glucose Concentrations on Small RNA Levels and Adherence of Streptococcus mutans.

Streptococcus mutans (S. mutans) adheres to the tooth surface, metabolizes carbohydrates, and produces acid products, leading to enamel demineralization-the onset of dental caries. Rapid acidification by S. mutans has been observed in the presence of glucose. However, little is known about the role of small RNAs (sRNAs) in S. mutans in the presence of glucose and their relationship to tooth adherence. The objective of this study was to evaluate the role of sRNAs in S. mutans (18-50 nucleotides) regarding adherence capacity under 1% and 5% glucose concentrations. The pH drop and adherence capacity in the 1% glucose condition were similar to these parameters under conditions of 5% sucrose that were published in our previous study. A total of 2149 candidate sRNA with at least 100 average reads in the 5% and 1% glucose libraries were obtained. Between the two libraries, 581 sRNAs were differentially expressed and 43 sRNAs were verified. However, the expression levels of the predicted target genes gtfC and spaP were similar between the 1% and 5% glucose conditions. The bioinformatic analysis suggested that differentially expressed sRNAs may be involved in several pathways. These findings indicate that sRNAs were induced under these glucose concentrations and a series of sRNAs were specifically induced, respectively. sRNAs that are induced under glucose stress may be involved in regulating adherence of S. mutans.