Streptococcus mutans Genome sequencing and assembly

Pan-genome refers to the sum of genes that can be found in a given bacterial species, including core-genome and dispensable genome. In this study, we compared the genomes of 183 streptococcus mutans (S.mutans) isolates from the perspective of pan-genome. It's demonstrated that S. mutans has an “open” pan-genome, which implies that there are plenty of new genes to be found with more and more genomes sequenced. Besides, S. mutans has a limited core-genome, most of which are genes related with vital activities of the species such as metabolism and heredity. In addition, core genes suffer larger selection pressures compared with those that are less widely distributed. Not surprisingly, we did't find absolutely specific virulence factors of this organism, indicating that it's several factors rather than only one that account for cariogenesis. These results will contribute to understanding the evolutionary characteristics and dynamic changes of genome components of the species. They also help to form the theoretical foundations for the prevention of dental caries. Furthermore, our study sets an example of analyzing big genomic datasets of pathogens from the view of pan-genome.