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Ann Biol Sci, 2017
ISSN: 2348-1927
August 23-24, 2017 | Toronto, Canada
Annual Conference on
MICROBIAL PATHOGENESIS, INFECTIOUS DISEASE,
ANTIMICROBIALS AND DRUG RESISTANCE
S
treptococcus mutans
is a primary etiological agent of
dental caries worldwide. Natural life of
S. mutans
in
dental biofilms often faces life-threatening insults, such as
killing by antibiotics or innate defense molecules produced
by competing species or by the host. How such insults affect
physiology and virulence of
S. mutans
is poorly understood. In
this study, we explored this question by analyzing the effects
of sub-MIC concentrations of bacitracin and ß-defensin 3 on
S. mutans. Microarray analysis showed that both bacitracin
and ß-defensin 3 induced differential expression of subsets
of genes that were largely regulated by the BceABRS four-
component system. The results were further confirmed by
examining gene expression profiles of selected genes or
genetic loci using qRT-PCR. We then examined the effects
of gene deletion of
bceRS
on the peptide antibiotics and
virulence. The results showed that a deletion of
bceRS
resulted in a mutant that was sensitive to bacitracin or
ß-defensin 3. Introduction of a wild copy of
becRS
in trans
(complementation) restored the wild type phenotype of the
mutant. In particular, both peptide antibiotics at a sub-MIC
induced biofilmformation in the parent but not in themutant.
A competitive fitness analysis showed that the mutant was
unable to compete with the parent for co-existence in
duel-strain mixed cultures in the presence of bacitracin. In
conclusion, the BceABRS four-component system controls a
regulon that is required for sensing, response and resistance
to bacitracin and ß-defensin. This system may play an
important role in adaptation and virulence expression of
S.
mutans
in dental biofilms.
Speaker Biography
Yung-Hua Li received his Doctorate in Molecular Microbiology at University of
Manitoba. Following his Post-doctoral fellowships in the University of British Columbia
and University of Rochester, NY, he worked as a Scientist in the University of Toronto,
with his research focus on molecular dissection of microbial biofilms. In 2004, he
joined the Faculties of Dentistry and Medicine at Dalhousie University, where he
has been directing a research team on genetic analyses of bacterial biofilms, biofilm
ecology and pathogenesis.
e:
yung-hua.li@dal.caThe BceABRS four-component system essential for bacitracin sensing and response is required for
biofilm formation and virulence of
Streptococcus mutans
Yung-Hua Li, David Ropson, Anton Dugandzic
and
Xiao-Lin Tian
Dalhousie University, Canada
Yung-Hua Li et al., Arch Clin Microbiol, 8:5
DOI: 10.4172/1989-8436-C1-003