?fruB effects on the transcriptome of Streptococcus mutans probed by RNA-seq

Streptococcus mutans, the primary etiologic agent of human dental caries, and a variety of oral Streptococcus and Actinomyces spp. synthesize high molecular mass homopolymers of fructose (fructans) with predominantly ß2,1- (inulins) or ß2,6-linkages (levans). The ability of S. mutans to degrade fructans contributes to the severity of dental caries. The extracellular product of fruA of S. mutans is an exo-ß-D-fructofuranosidase that releases fructose from levan and inulin. Located 70 bp downstream of fruA, fruB encodes a member of the glycoside hydrolase family 32, but the function of FruB has not been established.In this study, the transcriptomic analysis of UA159 and a fruB mutant grown on 0.2% levan revealed differential expression of genes encoding ABC transporters, transcriptional regulators and genes involved in growth and stress tolerance. The results provide new insights into the mechanisms of action by which FruB utilizes homo-polymers of fructose, specifically levan. The findings significantly enhance our understanding of the genetics and physiology of this cariogenic pathogen S. mutans. Overall design: mRNA profiling of S. mutans UA159 WT and ?fruB inTryptone-Vitamin (TV) medium supplemented with 0.2% levan.