Title: 0168 - Investigating the Role of MreCD in Cell Elongation and Stress Survival in Streptococcus mutans


Victor Chan (Presenter)
University of Florida

Robert Shields, University of Florida
Robert Burne, University of Florida


Objectives: Streptococcus mutans is a primary etiological agent of dental caries, and can cause other systemic infections. We sought to identify novel targets for antimicrobial therapies against S. mutans.

Methods: Using transposon mutagenesis combined with transposon sequencing (Tn-seq), a library of mutant S. mutans derived from strain UA159 was screened for fitness in defined and complex media. Deletion:replacement mutations were created in the genomically distinct clinical isolates UA159, Smu20, and Smu93, which were viewed by scanning electron microscopy and analyzed using ImageJ. The ability of the mutants to compete with the parent in acidic (pH 5.5) and aerobic conditions was evaluated, as were antagonistic interactions between S. mutans strains and oral commensal streptococci. Live-dead staining coupled with confocal microscopy was used to examine biofilm architecture and cell viability. Preliminary studies to examine the effects of MreCD on cell wall-associated proteins was done by 2D gel electrophoresis.

Results: Mutations in the genes encoding the cell division control proteins MreC and MreD were over-represented in Tn-Seq following passage. Cell width increased (P<0.0001) and cell length decreased (P<0.0001) in the mreCD mutants of UA159 and Smu93. The wild type outcompeted the mutant in the Smu20 and Smu93 genetic backgrounds at low pH (P<0.05), and all mutants were more competitive in aerobic conditions. However, the mreCD mutant of S. mutans had a decreased ability to antagonize growth of Streptococcus gordonii and Streptococcus sanguinis. Biofilm biomass accumulation by the mreCD mutant markedly decreased in the Smu20 background, but UA159- and Smu93-derived mreCD mutants displayed altered biofilm architecture and enhanced viability.

Conclusions: MreCD play essential roles in determining cell shape and in physiologic processes that are central to the ability of S. mutans to cause disease. Future studies will focus on understanding the mechanisms by which MreCD influence stress tolerance, biofilm formation, and antagonism of commensals.

Student Presenter

This abstract is based on research that was funded entirely or partially by an outside source:
R01 DE13239, R01 DE25832, and UFCD DMD Summer Research Program

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE

Sponsoring Group/Network