Effect of iron on the expression of sirR and sitABC in biofilm-associated Staphylococcus epidermidis.
BACKGROUND
Different gene expression patterns correlate with the altered phenotype in biofilm-associated bacteria. Iron and iron-linked genes are thought to play a key-role in biofilm formation. The expression of Fe-linked genes (sirR, sitABC operon) in Staphylococcus epidermidis, was compared in planktonic versus sessile bacteria in vitro and in vivo in a subcutaneous foreign body rat model.


RESULTS
In vitro in a Fe-limited environment, the planktonic form of S. epidermidis produces siderophores and grows slower than in Fe-rich environment. The expression of sirR in planktonic bacteria, in vitro, was not different in medium without Fe or with 1 microM FeCl3. High Fe concentrations (25 microM FeCl3) increased expression of sirR transiently during the early phase of incubation. Expression of sitC in vitro, in planktonic bacteria, was inversely correlated with sirR expression in medium with 25 microM FeCl3: sitC expression decreased for the first 3 hours followed by an up regulation.In sessile bacteria in vitro, sirR expression was high and independent of the Fe concentration. The expression of sitC was not inversely correlated to sirR expression. In vivo, expression levels of sirR and of sitABC were high during the initial phase after implantation and, after a transient decrease, remained stable over a period of two weeks.


CONCLUSIONS
Our data suggest that the expression of sirR and the regulatory effect of sirR on the sitABC operon are different in planktonic and sessile bacteria.
Massonet
Caroline
C
Lab medical microbiology, Department Medical Diagnostic Sciences, KULeuven, U,Z,Gasthuisberg, Herestraat 49 CDG8th floor, B-3000, Leuven, Belgium. caroline.massonet@med.kuleuven.be
Pintens
Valerie
V
Merckx
Rita
R
Anné
Jozef
J
Lammertyn
Elke
E
Van Eldere
Johan
J
D000704:Analysis of Variance; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002712:Chlorides; D003470:Culture Media / Q000494:pharmacology; D004269:DNA, Bacterial / Q000235:genetics; D005290:Ferric Compounds / Q000494:pharmacology; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial / Q000235:genetics; D007501:Iron / Q000494:pharmacology*; D007700:Kinetics; D009876:Operon / Q000235:genetics*; D016133:Polymerase Chain Reaction; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017262:Siderophores / Q000378:metabolism; D013203:Staphylococcal Infections / Q000382:microbiology; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D002712:Chlorides; D003470:Culture Media; D004269:DNA, Bacterial; D005290:Ferric Compounds; D012097:Repressor Proteins; D017262:Siderophores; C114524:SirR protein, Staphylococcus epidermidis; D007501:Iron; C024555:ferric chloride