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Open Access Research article

A genome-wide study of two-component signal transduction systems in eight newly sequenced mutans streptococci strains

Lifu Song14, Padhmanand Sudhakar1, Wei Wang1*, Georg Conrads2, Anke Brock2, Jibin Sun1, Irene Wagner-Döbler3 and An-Ping Zeng1*

Author Affiliations

1 Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany

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

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

4 Tianjin Institute of Industrial Biotechnology, Chinese Academy of Science, Tianjin 300308, Peoples Republic of China

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BMC Genomics 2012, 13:128  doi:10.1186/1471-2164-13-128

Published: 4 April 2012

Abstract

Background

Mutans streptococci are a group of gram-positive bacteria including the primary cariogenic dental pathogen Streptococcus mutans and closely related species. Two component systems (TCSs) composed of a signal sensing histidine kinase (HK) and a response regulator (RR) play key roles in pathogenicity, but have not been comparatively studied for these oral bacterial pathogens.

Results

HKs and RRs of 8 newly sequenced mutans streptococci strains, including S. sobrinus DSM20742, S. ratti DSM20564 and six S. mutans strains, were identified and compared to the TCSs of S. mutans UA159 and NN2025, two previously genome sequenced S. mutans strains. Ortholog analysis revealed 18 TCS clusters (HK-RR pairs), 2 orphan HKs and 2 orphan RRs, of which 8 TCS clusters were common to all 10 strains, 6 were absent in one or more strains, and the other 4 were exclusive to individual strains. Further classification of the predicted HKs and RRs revealed interesting aspects of their putative functions. While TCS complements were comparable within the six S. mutans strains, S. sobrinus DSM20742 lacked TCSs possibly involved in acid tolerance and fructan catabolism, and S. ratti DSM20564 possessed 3 unique TCSs but lacked the quorum-sensing related TCS (ComDE). Selected computational predictions were verified by PCR experiments.

Conclusions

Differences in the TCS repertoires of mutans streptococci strains, especially those of S. sobrinus and S. ratti in comparison to S. mutans, imply differences in their response mechanisms for survival in the dynamic oral environment. This genomic level study of TCSs should help in understanding the pathogenicity of these mutans streptococci strains.

Keywords:
Mutans streptococci; Streptococcus mutans; Streptococcus ratti; Streptococcus sobrinus; Two-component system; Histidine kinase; Response regulator; Signal transduction; Comparative genomics