The goal of this project is to determine the genome sequence of Streptococcus sobrinus 6715, an oral bacterium associated with the formation of dental caries. Streptococcus sobrinus is one of the early colonizing oral bacteria that play a significant role in adherence to the tooth surface, and also in coaggregations with other types of bacteria to form plaque. Binding to the host derived protein layer that covers the tooth surface allows S. sobrinus and related streptococci to inititate colonization of the oral cavity. The highly aciduronic nature of S. sobrinus allows the organism to continue producing acid as the pH in its environment lowers. As acid production is important to the release of calcium phosphates from the tooth enamel, and the subsequent formation of caries, this unique ability of S. sobrinus to continue reducing environmental pH is significant to a complete understanding of periodontal disease. Recent advances in whole genome sequencing now make it possible to obtain the complete genome sequence of the 2.20 Mbp genome of S. sobrinus 6715. The complete sequence along with a complementary set of clones will provide a tremendous resource in being able to understand the biology of S. sobrinus. The proposed project will encompass: i) construction of random small and medium insert plasmid libraries and a large insert BAC library from S. sobrinus 6715; ii) sequencing of both ends of approximately 21,333 small and medium insert clones; iii) sequencing the ends of a set of BAC clones clones to provide a genome scaffold to order contigs, and reduce the effort needed for gap closure; and iv) assembly and annotation of the genome to identify structural features, and assign gene functional roles to open reading frames, based on database similarity searches. This whole genome sequencing project will complement the ongoing sequencing and analysis of the related streptococci Streptococcus pneumoniae, S. pyogenes, S. agalactiae, and S. mutans, and will allow for the identification of factors unique to these organisms. The project will also allow for the understanding of the pathogenic mechanisms used by S. sobrinus to successfully colonize the oral cavity. The data generated from this project will be deposited in public databases, including the TIGR World Wide Web Site. In addition, the libraries and overlapping BAC clone sets used to generate the complete genome sequence will be made available to the research community.
