title: Comparing the cariogenic species Streptococcus sobrinus and S. mutans on whole genome level.
abstract: BACKGROUND
  Two closely related species of mutans streptococci, namely Streptococcus mutans and Streptococcus sobrinus, are associated with dental caries in humans. Their acidogenic and aciduric capacity is directly associated with the cariogenic potential of these bacteria. To survive acidic and temporarily harsh conditions in the human oral cavity with hundreds of other microbial co-colonizers as competitors, both species have developed numerous mechanisms for adaptation.
  
  
  OBJECTIVE
  The recently published novel genome information for both species is used to elucidate genetic similarities but especially differences and to discuss the impact on cariogenicity of the corresponding phenotypic properties including adhesion, carbohydrate uptake and fermentation, acid tolerance, signaling by two component systems, competence, and oxidative stress resistance.
  
  
  CONCLUSIONS
  S. sobrinus can down-regulate the SpaA-mediated adherence to the pellicle. It has a smaller number of two-component signaling systems and bacteriocin-related genes than S. mutans, but all or even more immunity proteins. It lacks the central competence genes comC, comS, and comR. There are more genes coding for glucosyltransferases and a novel energy production pathway formed by lactate oxidase, which is not found in S. mutans. Both species show considerable differences in the regulation of fructan catabolism. However, both S. mutans and S. sobrinus share most of these traits and should therefore be considered as equally virulent with regard to dental caries.
authors.affiliation: Division of Oral Microbiology and Immunology, Department of Operative and Preventive Dentistry & Periodontology, RWTH Aachen University Hospital, Aachen, Germany; gconrads@ukaachen.de.
authors.forename: Georg
authors.initials: G
authors.lastname: Conrads
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands.
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: de Soet
authors.affiliation: Institute of Bioprocess and Biosystems, Technical University Hamburg, Harburg, Germany.
authors.forename: Lifu
authors.initials: L
authors.lastname: Song
authors.affiliation: Division of Oral Microbiology and Immunology, Department of Operative and Preventive Dentistry & Periodontology, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Henne
authors.affiliation: Helmholtz-Centre for Infection Research, Group Microbial Communication, Division of Microbial Pathogenesis, Braunschweig, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Sztajer
authors.affiliation: Helmholtz-Centre for Infection Research, Group Microbial Communication, Division of Microbial Pathogenesis, Braunschweig, Germany.
authors.forename: Irene
authors.initials: I
authors.lastname: Wagner-Döbler
authors.affiliation: Institute of Bioprocess and Biosystems, Technical University Hamburg, Harburg, Germany.
authors.forename: An-Ping
authors.initials: AP
authors.lastname: Zeng
keywords: Mutans streptococci; adhesion; bacteriocins; cariogenicity; comparative genomics; competence; sugar metabolism; two-component-systems