Affiliation:
1. Department of Microbiology, RCSI Education and Research Centre, Beaumont Hospital, Royal College of Surgeons in Ireland, Dublin 9, Ireland
Abstract
ABSTRACT
Biofilm formation in
Staphylococcus epidermidis
is dependent upon the
ica
operon-encoded polysaccharide intercellular adhesin, which is subject to phase-variable and environmental regulation. The
icaR
gene, located adjacent to the
ica
operon, appears to be a member of the
tetR
family of transcriptional regulators. In the reference strain RP62A, reversible inactivation of the
ica
operon by IS
256
accounts for 25 to 33% of phase variants. In this study,
icaA
and
icaR
regulation were compared in RP62A and a biofilm-forming clinical isolate, CSF41498, in which IS
256
is absent. Predictably,
ica
operon expression was detected only in wild-type CSF41498 and RP62A but not in non-IS
256
-generated phase variants. In contrast, the
icaR
gene was not expressed in RP62A phase variants but was expressed in CSF41498 variants. An
icaR
::Em
r
insertion mutation in CSF41498 resulted in an at least a 5.8-fold increase in
ica
operon expression but did not significantly alter regulation of the
icaR
gene itself. Activation of
ica
operon transcription by ethanol in CSF41498 was
icaR
dependent. In contrast, a small but significant induction of
ica
by NaCl and glucose (NaCl-glucose) was observed in the
icaR
::Em
r
mutant. In addition, transcription of the
icaR
gene itself was not significantly affected by NaCl-glucose but was repressed by ethanol. Expression of the
ica
operon was induced by ethanol or NaCl-glucose in phase variants of CSF41498 (
icaR
+
) but not in RP62A variants (
icaR
deficient). These data indicate that
icaR
encodes a repressor of
ica
operon transcription required for ethanol but not NaCl-glucose activation of
ica
operon expression and biofilm formation.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
254 articles.
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