Affiliation:
1. Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida 32610
Abstract
ABSTRACT
Genetic competence appears to be important in establishment of biofilms and tolerance of environmental insults. We report here that the development of competence is controlled at multiple levels in a complex network that includes two signal-transducing two-component systems (TCS). Using
Streptococcus mutans
strain UA159, we demonstrate that the histidine kinase CiaH, but not the response regulator CiaR, causes a dramatic decrease in biofilm formation and in transformation efficiency. Inactivation of
comE
or
comD
had no effect on stress tolerance, but transformability of the mutants was poor and was not restored by addition of competence-stimulating peptide (CSP). Horse serum (HS) or bovine serum albumin (BSA) had no impact on transformability of any strains. Interestingly, though, the presence of HS or BSA in combination with CSP was required for efficient induction of
comD
,
comX
, and
comYA
, and induction was dependent on ComDE and CiaH, but not CiaR. Inactivation of
comC
, encoding CSP, had no impact on transformation, and CiaH was shown to be required for optimal
comC
expression. This study reveals that
S. mutans
integrates multiple environmental signals through CiaHR and ComDE to coordinate induction of
com
genes and that CiaH can exert its influence through CiaR and as-yet-unidentified regulators. The results highlight critical differences in the role and regulation of CiaRH and
com
genes in different
S. mutans
isolates and between
S. mutans
and
Streptococcus pneumoniae
, indicating that substantial divergence in the role and regulation of TCS and competence genes has occurred in streptococci.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
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5. Oral Streptococci... Products of Their Environment
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