Whole Genome Sequencing Of The Fluoride-resistant Strain Of Streptococcus Mutans

Objective：Tooth decay is a chronic progressive destructive disease, which occurres in toothhard tissues,andwhich is caused by bacterias mainly.This disease is one of twocommon diseases in the oral cavity. Its pathological manifestations are thatdemineralization of the inorganic and the organic decomposition. Tooth decay is amutifactor disease, and among factors,bacteria is the primary cause, only the existenceof Streptococcus mutans is associated with human caries disease. In addition,it isreported that caries disease is the most expensive infection for most people in life. Inrecent years, fluoride has been widely used in clinical treatment of tooth decay,but thelong-term use of a large amount of fluoride may lead to the emergence offluoride-resistant Streptococcus mutans strain, and some scholars have successfullyinduced fluoride-resistant Streptococcus mutans strain in vitro. Studies haveconfirmed that fluoride-resistant Streptococcus mutans strain has stronger ability ofcaries than parental strain. Scholars are limintted to do the reaserch of many relatedacid tolerance genes,such as ffh、dgk、dltCandCcpA,but have to do further reaserchof other virlence factors. The genome sequence of Streptococcus mutans UA159hasbeen finished,and the accession no.AE014133. The genome sequence offluoride-resistant Streptococcus mutans strain in the molecular level can identifymutations of genes and encoded proteins,which lay foundation for the application offluoride and provide certain theoretical and experimental basis for further reaserchof prevention drugs and screening drug caries.Metheds:1.Screening and identification of fluoride-resistant Streptococcus mutansUA159-FR.2.The extraction of the whole genome of UA159-FR.3.By the Illumina Hiseq2000and PACBIO RS sequencingtechnology, Illumina Hiseq2000PE library (300~500bp), MP library (KB) and aPACBIO library (8~10KB) have been respectively constructed, then quality control was carried out on the sequencing of the data obtained,and complete the wholegenome sequencing and genome mapping of this strain.4.Comparing fluoride-resistant Streptococcus mutans UA159-FR and referencedstrain UA159, then doing bioinformatic analysis.Results:1.cultured bacteria in the experiment is identified as fluoride-resistantStreptococcus mutans UA159-FR.2.The whole genome sequence of UA159-FR has been obtained,and genomemapping has been completed.3.At the genome level, Phylogenetic tree of5strains is construced which is basedon neighbour－joining analysis.4. Comparing1878genes of UA159-FR and genes of UA159,it is found that20genes have mutated. Among them, orf00385、orf00876、orf01053、orf1135andorf01258belong to Synonymous mutations; orf00091、orf00875、orf00929、orf00986、orf01042、orf01092、orf01190and orf01600belong to missense mutation; orf01786belong to frameshift mutations; orf00032、orf00544、orf00585、orf01127、orf01130and orf01759belong to terminate the password mutation. Genes related to adhesion ofStreptococcus mutans (2genes): orf00875（glucosyltransferase-I）; orf00876(glucosyltransferase-Si). Genes related to acid production (one gene): orf00585(citratesynthase), orf01092(enolase).5.Five intergenic regions have base substitution and insert.6.The whole genome of Streptococcus mutans UA159-FR has been submitted toGenbank, and obtain the accession number: CP007016.Conclusion:Whole genome sequencing of Streptococcus mutans UA159-FR has successfullycompleted. Genes mutations and intergenic regions have been determined, and thesignificances of these mutations have also been determined. It is supposed that theenhancement of cariogenicity is possibly associated with operons and DNA methylation. These discoveries provide certain theoretical and experimental basis forfurther reaserch of prevention drugs and screening drug caries.