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Open Access Highly Accessed Research article

Genetic variability of mutans streptococci revealed by wide whole-genome sequencing

Lifu Song1, Wei Wang1*, Georg Conrads2, Anke Rheinberg2, Helena Sztajer3, Michael Reck3, Irene Wagner-Döbler3 and An-Ping Zeng1*

Author Affiliations

1 Institute of Bioprocess and Biosystems, Technical University Hamburg Harburg, Hamburg Harburg, Germany

2 Division of Oral Microbiology and Immunology, Department of Operative and Preventive Dentistry & Periodontology, RWTH Aachen University, RWTH Aachen, Germany

3 Helmholtz-Centre for Infection Research, Group Microbial Communication, Division of Microbial Pathogenesis, Inhoffenstr. 7, Braunschweig, 38124, Germany

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BMC Genomics 2013, 14:430  doi:10.1186/1471-2164-14-430

Published: 28 June 2013

Abstract

Background

Mutans streptococci are a group of bacteria significantly contributing to tooth decay. Their genetic variability is however still not well understood.

Results

Genomes of 6 clinical S. mutans isolates of different origins, one isolate of S. sobrinus (DSM 20742) and one isolate of S. ratti (DSM 20564) were sequenced and comparatively analyzed. Genome alignment revealed a mosaic-like structure of genome arrangement. Genes related to pathogenicity are found to have high variations among the strains, whereas genes for oxidative stress resistance are well conserved, indicating the importance of this trait in the dental biofilm community. Analysis of genome-scale metabolic networks revealed significant differences in 42 pathways. A striking dissimilarity is the unique presence of two lactate oxidases in S. sobrinus DSM 20742, probably indicating an unusual capability of this strain in producing H2O2 and expanding its ecological niche. In addition, lactate oxidases may form with other enzymes a novel energetic pathway in S. sobrinus DSM 20742 that can remedy its deficiency in citrate utilization pathway.

Using 67 S. mutans genomes currently available including the strains sequenced in this study, we estimates the theoretical core genome size of S. mutans, and performed modeling of S. mutans pan-genome by applying different fitting models. An “open” pan-genome was inferred.

Conclusions

The comparative genome analyses revealed diversities in the mutans streptococci group, especially with respect to the virulence related genes and metabolic pathways. The results are helpful for better understanding the evolution and adaptive mechanisms of these oral pathogen microorganisms and for combating them.

Keywords:
Mutans Streptococci; Streptococcus Mutans; Streptococcus Ratti; Streptococcus Sobrinus; Comparative Genomics; Core-genome; Pan-genome; Pathogenicity; Lactate Oxidase; Metabolic Network