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Effect of iron on the expression of sirR and sitABC in biofilm-associated Staphylococcus epidermidis.

Massonet C, Pintens V, Merckx R, Anné J, Lammertyn E, Van Eldere J - BMC Microbiol. (2006)

Bottom Line: 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 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lab medical microbiology, Department Medical Diagnostic Sciences, KULeuven, U,Z,Gasthuisberg, Herestraat 49 CDG8th floor, B-3000, Leuven, Belgium. caroline.massonet@med.kuleuven.be

ABSTRACT

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.

Conclusion: 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.

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In vitro gene expression of sirR (a) and sitC (b) in sessile versus planktonic bacteria. Gene expression is quantified as log10 (cDNA/gDNA) in the y-axis. Time is given in hours in the x-axis. The line that links the data points helps to clarify the results at each time point measured. The error bars represent standard deviations. Fifteen samples from three independent cultures were assessed at each time point. Bacteria were pre-incubated overnight in fRPMI and incubated together with catheter fragments in fRPMI (sessile: dotted line with empty squares; planktonic: dotted line with filled diamonds) or in fRPMI-Fe25 (sessile: full line with crosses; planktonic: full line with empty triangles).
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Figure 4: In vitro gene expression of sirR (a) and sitC (b) in sessile versus planktonic bacteria. Gene expression is quantified as log10 (cDNA/gDNA) in the y-axis. Time is given in hours in the x-axis. The line that links the data points helps to clarify the results at each time point measured. The error bars represent standard deviations. Fifteen samples from three independent cultures were assessed at each time point. Bacteria were pre-incubated overnight in fRPMI and incubated together with catheter fragments in fRPMI (sessile: dotted line with empty squares; planktonic: dotted line with filled diamonds) or in fRPMI-Fe25 (sessile: full line with crosses; planktonic: full line with empty triangles).

Mentions: Initially, a significantly increased expression of sirR was observed both in planktonic and sessile bacteria in fRPMI-Fe25 (Fig. 4a). This increase was more pronounced in planktonic than in sessile bacteria (two-way ANOVA; Bonferroni; p < 0.01). After this initial phase, expression was similar, independent of the Fe concentration or growth mode of the bacteria. At t = 6 hrs the expression of sirR in sessile bacteria in fRPMI-Fe25 increased significantly (two-way ANOVA; Bonferroni; p < 0.001) in contrast to the expression of sirR in planktonic bacteria in the same medium which decreased (one-way ANOVA; Bonferroni; p < 0.001).


Effect of iron on the expression of sirR and sitABC in biofilm-associated Staphylococcus epidermidis.

Massonet C, Pintens V, Merckx R, Anné J, Lammertyn E, Van Eldere J - BMC Microbiol. (2006)

In vitro gene expression of sirR (a) and sitC (b) in sessile versus planktonic bacteria. Gene expression is quantified as log10 (cDNA/gDNA) in the y-axis. Time is given in hours in the x-axis. The line that links the data points helps to clarify the results at each time point measured. The error bars represent standard deviations. Fifteen samples from three independent cultures were assessed at each time point. Bacteria were pre-incubated overnight in fRPMI and incubated together with catheter fragments in fRPMI (sessile: dotted line with empty squares; planktonic: dotted line with filled diamonds) or in fRPMI-Fe25 (sessile: full line with crosses; planktonic: full line with empty triangles).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1764749&req=5

Figure 4: In vitro gene expression of sirR (a) and sitC (b) in sessile versus planktonic bacteria. Gene expression is quantified as log10 (cDNA/gDNA) in the y-axis. Time is given in hours in the x-axis. The line that links the data points helps to clarify the results at each time point measured. The error bars represent standard deviations. Fifteen samples from three independent cultures were assessed at each time point. Bacteria were pre-incubated overnight in fRPMI and incubated together with catheter fragments in fRPMI (sessile: dotted line with empty squares; planktonic: dotted line with filled diamonds) or in fRPMI-Fe25 (sessile: full line with crosses; planktonic: full line with empty triangles).
Mentions: Initially, a significantly increased expression of sirR was observed both in planktonic and sessile bacteria in fRPMI-Fe25 (Fig. 4a). This increase was more pronounced in planktonic than in sessile bacteria (two-way ANOVA; Bonferroni; p < 0.01). After this initial phase, expression was similar, independent of the Fe concentration or growth mode of the bacteria. At t = 6 hrs the expression of sirR in sessile bacteria in fRPMI-Fe25 increased significantly (two-way ANOVA; Bonferroni; p < 0.001) in contrast to the expression of sirR in planktonic bacteria in the same medium which decreased (one-way ANOVA; Bonferroni; p < 0.001).

Bottom Line: 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 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lab medical microbiology, Department Medical Diagnostic Sciences, KULeuven, U,Z,Gasthuisberg, Herestraat 49 CDG8th floor, B-3000, Leuven, Belgium. caroline.massonet@med.kuleuven.be

ABSTRACT

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.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus