Affiliation:
1. Institut für Medizinische Mikrobiologie und Immunologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
Abstract
ABSTRACT
Staphylococcus epidermidis
is a common pathogen in medical device-associated infections. Its major pathogenetic factor is the ability to form adherent biofilms. The polysaccharide intercellular adhesin (PIA), which is synthesized by the products of the
icaADBC
gene cluster, is essential for biofilm accumulation. In the present study, we characterized the gene locus inactivated by Tn
917
insertions of two isogenic,
icaADBC
-independent, biofilm-negative mutants, M15 and M19, of the biofilm-producing bacterium
S. epidermidis
1457. The insertion site was the same in both of the mutants and was located in the first gene,
rsbU
, of an operon highly homologous to the
sigB
operons of
Staphylococcus aureus
and
Bacillus subtilis
. Supplementation of Trypticase soy broth with NaCl (TSB
NaCl
) or ethanol (TSB
EtOH
), both of which are known activators of
sigB
, led to increased biofilm formation and PIA synthesis by
S. epidermidis
1457. Insertion of Tn
917
into
rsbU
, a positive regulator of alternative sigma factor ς
B
, led to a biofilm-negative phenotype and almost undetectable PIA production. Interestingly, in TSB
EtOH
, the mutants were enabled to form a biofilm again with phenotypes similar to those of the wild type. In TSB
NaCl
, the mutants still displayed a biofilm-negative phenotype. No difference in primary attachment between the mutants and the wild type was observed. Similar phenotypic changes were observed after transfer of the Tn
917
insertion of mutant M15 to the independent and biofilm-producing strain
S. epidermidis
8400. In 11 clinical
S. epidermidis
strains, a restriction fragment length polymorphism of the
sigB
operon was detected which was independent of the presence of the
icaADBC
locus and a biofilm-positive phenotype. Obviously, different mechanisms are operative in the regulation of PIA expression in stationary phase and under stress induced by salt or ethanol.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
247 articles.
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