Small RNAs in streptococci.

The group of streptococci includes species responsible for severe diseases in humans. To adapt to their environment and infect their hosts, streptococci depend on precise regulation of gene expression. The last decade has witnessed increasing findings of small RNAs (sRNAs) having regulatory functions in bacteria. More recently, genome-wide screens revealed that streptococcal genomes also encode multiple sRNAs. Some sRNAs including the class of CRISPR RNAs (crRNAs) play critical roles in streptococcal adaptation and virulence. Analysis of sRNA mechanisms uncovered three sRNAs that target in trans mRNA (FasX), sRNA (tracrRNA) and DNA (crRNA). Overall, the current understanding of sRNA-mediated regulation in streptococci remains very limited. Given the complexity of regulatory networks and the number of recently predicted sRNAs, future research should reveal new functions and mechanisms for the streptococcal sRNAs. Here, we provide a comprehensive summary of the information available on the topic.