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Title: Genomic instability of TnSMU2 contributes to Streptococcus mutans biofilm development and competence in a cidB mutant
Abstract

Streptococcus mutansis a key pathogenic bacterium in the oral cavity and a primary contributor to dental caries. TheS. mutansCid/Lrg system likely contributes to tolerating stresses encountered in this environment ascidand/orlrgmutants exhibit altered oxidative stress sensitivity, genetic competence, and biofilm phenotypes. It was recently noted that thecidBmutant had two stable colony morphologies: a “rough” phenotype (similar to wild type) and a “smooth” phenotype. In our previously published work, thecidBrough mutant exhibited increased sensitivity to oxidative stress, and RNAseq identified widespread transcriptomic changes in central carbon metabolism and oxidative stress response genes. In this current report, we conducted Illumina‐based genome resequencing of wild type,cidBrough, andcidBsmooth mutants and compared their resistance to oxidative and acid stress, biofilm formation, and competence phenotypes. BothcidBmutants exhibited comparable aerobic growth inhibition on agar plates, during planktonic growth, and in the presence of 1 mM hydrogen peroxide. ThecidBsmooth mutant displayed a significant competence defect in BHI, which was rescuable by synthetic CSP. BothcidBmutants also displayed reduced XIP‐mediated competence, although this reduction was more pronounced in thecidBsmooth mutant. Anaerobic biofilms of thecidBsmooth mutant displayed increased propidium iodide staining, but corresponding biofilm CFU data suggest this phenotype is due to cell damage and not increased cell death. ThecidBrough anaerobic biofilms showed altered structure relative to wild type (reduced biomass and average thickness) which correlated with decreased CFU counts. Sequencing data revealed that thecidBsmooth mutant has a unique “loss of read coverage” of ~78 kb of DNA, corresponding to the genomic island TnSMU2 and genes flanking its 3′ end. It is therefore likely that the unique biofilm and competence phenotypes of thecidBsmooth mutant are related to its genomic changes in this region.

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NSF-PAR ID:
10459446
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
MicrobiologyOpen
Volume:
8
Issue:
12
ISSN:
2045-8827
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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