Quorum sensing of Streptococcus mutans is activated by Aggregatibacter actinomycetemcomitans and by the periodontal microbiome.
The oral cavity is inhabited by complex microbial communities forming biofilms that can cause caries and periodontitis. Cell-cell communication might play an important role in modulating the physiologies of individual species, but evidence so far is limited.



Here we demonstrate that a pathogen of the oral cavity, Aggregatibacter actinomycetemcomitans (A. act.), triggers expression of the quorum sensing (QS) regulon of Streptococcus mutans, a well-studied model organism for cariogenic streptococci, in dual-species biofilms grown on artificial saliva. The gene for the synthesis of the QS signal XIP is essential for this interaction. Transcriptome sequencing of biofilms revealed that S. mutans up-regulated the complete QS regulon (transformasome and mutacins) in the presence of A. act. and down-regulated oxidative stress related genes. A.act. required the presence of S. mutans for growth. Fimbriae and toxins were its most highly expressed genes and up-regulation of anaerobic metabolism, chaperones and iron acquisition genes was observed in co-culture. Metatranscriptomes from periodontal pockets showed highly variable levels of S. mutans and low levels of A. act.. Transcripts of the alternative sigma-factor SigX, the key regulator of QS in S. mutans, were significantly enriched in periodontal pockets compared to single cultures (log24.159, FDR ≤0.001, and expression of mutacin related genes and transformasome components could be detected.



The data show that the complete QS regulon of S. mutans can be induced by an unrelated oral pathogen and S. mutans may be competent in oral biofilms in vivo.
Microbial Communication, Helmholtz-Center for Infection Research, Braunschweig, Germany.|Present address: Hannover Medical School (MHH), Hannover, Germany.
Szymon P
SP
Szafrański
Microbial Communication, Helmholtz-Center for Infection Research, Braunschweig, Germany.
Zhi-Luo
ZL
Deng
Microbial Communication, Helmholtz-Center for Infection Research, Braunschweig, Germany.
Jürgen
J
Tomasch
Genome Analytics, Helmholtz Centre for Infection Research, Braunschweig, Germany.
Michael
M
Jarek
Genome Analytics, Helmholtz Centre for Infection Research, Braunschweig, Germany.
Sabin
S
Bhuju
Central Facility for Microscopy, Helmholtz Centre for Infection Research, Braunschweig, Germany.
Manfred
M
Rohde
Microbial Communication, Helmholtz-Center for Infection Research, Braunschweig, Germany.
Helena
H
Sztajer
Microbial Communication, Helmholtz-Center for Infection Research, Braunschweig, Germany. Irene.Wagner-Doebler@helmholtz-hzi.de.
Irene
I
Wagner-Döbler
D016976:Aggregatibacter actinomycetemcomitans / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D056265:Microbial Interactions; D064307:Microbiota; D010514:Periodontal Pocket / Q000382:microbiology; D010519:Periodontium / Q000382:microbiology*; D053038:Quorum Sensing; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D013295:Streptococcus mutans / Q000502:physiology*; D059467:Transcriptome
D001426:Bacterial Proteins; D012808:Sigma Factor