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recA mediated spontaneous deletions of the icaADBC operon of clinical Staphylococcus epidermidis isolates: a new mechanism of phenotypic variations.

Nuryastuti T, van der Mei HC, Busscher HJ, Kuijer R, Aman AT, Krom BP - Antonie Van Leeuwenhoek (2008)

Bottom Line: Instead, in high frequency switching strains, spontaneous mutations in lexA were found which resulted in deregulation of recA expression, as shown by real time PCR.RecA is involved in genetic deletions and rearrangements and we postulate a model representing a new mechanism of phenotypic variation in clinical isolates of S. epidermidis.This is the first report of S. epidermidis strains irreversibly switching from biofilm-positive to biofilm-negative phenotype by spontaneous deletion of icaADBC.

View Article: PubMed Central - PubMed

Affiliation: Department of BioMedical Engineering (Sector F), University Medical Center Groningen and University of Groningen, PO box 196, 9700 AD Groningen, The Netherlands.

ABSTRACT
Phenotypic variation of Staphylococcus epidermidis involving the slime related ica operon results in heterogeneity in surface characteristics of individual bacteria in axenic cultures. Five clinical S. epidermidis isolates demonstrated phenotypic variation, i.e. both black and red colonies on Congo Red agar. Black colonies displayed bi-modal electrophoretic mobility distributions at pH 2, but such phenotypic variation was absent in red colonies of the same strain as well as in control strains without phenotypic variation. All red colonies had lost ica and the ability to form biofilms, in contrast to black colonies of the same strain. Real time PCR targeting icaA indicated a reduction in gene copy number within cultures exhibiting phenotypic variation, which correlated with phenotypic variations in biofilm formation and electrophoretic mobility distribution of cells within a culture. Loss of ica was irreversible and independent of the mobile element IS256. Instead, in high frequency switching strains, spontaneous mutations in lexA were found which resulted in deregulation of recA expression, as shown by real time PCR. RecA is involved in genetic deletions and rearrangements and we postulate a model representing a new mechanism of phenotypic variation in clinical isolates of S. epidermidis. This is the first report of S. epidermidis strains irreversibly switching from biofilm-positive to biofilm-negative phenotype by spontaneous deletion of icaADBC.

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Panel a: Quantitative biofilm formation of S. epidermidis strains, showing phenotypic variation and grown either from black colonies (indicated with B) or red colonies (indicated with R). Absorbances are means over triplicate wells (±standard deviations). Panels b and c show representative CLSM images of biofilms grown from a black colony (panel b) and a red colony (panel c) of strain 45
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Fig2: Panel a: Quantitative biofilm formation of S. epidermidis strains, showing phenotypic variation and grown either from black colonies (indicated with B) or red colonies (indicated with R). Absorbances are means over triplicate wells (±standard deviations). Panels b and c show representative CLSM images of biofilms grown from a black colony (panel b) and a red colony (panel c) of strain 45

Mentions: The ability of black and red variants to form biofilm was quantitatively assayed in microtiter plates. Black colonies grew thick biofilms, in contrast to red colonies that were poor biofilm formers (Fig. 2a). To exclude any effects of crystal violet bound by PIA (present in black, absent in red colonies), the biofilms were also studied by confocal laser scanning microscopy (CLSM) following Live/Dead staining (Fig. 2b, c). These results confirmed that the quantitative differences in biofilm formation after crystal violet staining were not associated with the presence or absence of PIA.Fig. 2


recA mediated spontaneous deletions of the icaADBC operon of clinical Staphylococcus epidermidis isolates: a new mechanism of phenotypic variations.

Nuryastuti T, van der Mei HC, Busscher HJ, Kuijer R, Aman AT, Krom BP - Antonie Van Leeuwenhoek (2008)

Panel a: Quantitative biofilm formation of S. epidermidis strains, showing phenotypic variation and grown either from black colonies (indicated with B) or red colonies (indicated with R). Absorbances are means over triplicate wells (±standard deviations). Panels b and c show representative CLSM images of biofilms grown from a black colony (panel b) and a red colony (panel c) of strain 45
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2480603&req=5

Fig2: Panel a: Quantitative biofilm formation of S. epidermidis strains, showing phenotypic variation and grown either from black colonies (indicated with B) or red colonies (indicated with R). Absorbances are means over triplicate wells (±standard deviations). Panels b and c show representative CLSM images of biofilms grown from a black colony (panel b) and a red colony (panel c) of strain 45
Mentions: The ability of black and red variants to form biofilm was quantitatively assayed in microtiter plates. Black colonies grew thick biofilms, in contrast to red colonies that were poor biofilm formers (Fig. 2a). To exclude any effects of crystal violet bound by PIA (present in black, absent in red colonies), the biofilms were also studied by confocal laser scanning microscopy (CLSM) following Live/Dead staining (Fig. 2b, c). These results confirmed that the quantitative differences in biofilm formation after crystal violet staining were not associated with the presence or absence of PIA.Fig. 2

Bottom Line: Instead, in high frequency switching strains, spontaneous mutations in lexA were found which resulted in deregulation of recA expression, as shown by real time PCR.RecA is involved in genetic deletions and rearrangements and we postulate a model representing a new mechanism of phenotypic variation in clinical isolates of S. epidermidis.This is the first report of S. epidermidis strains irreversibly switching from biofilm-positive to biofilm-negative phenotype by spontaneous deletion of icaADBC.

View Article: PubMed Central - PubMed

Affiliation: Department of BioMedical Engineering (Sector F), University Medical Center Groningen and University of Groningen, PO box 196, 9700 AD Groningen, The Netherlands.

ABSTRACT
Phenotypic variation of Staphylococcus epidermidis involving the slime related ica operon results in heterogeneity in surface characteristics of individual bacteria in axenic cultures. Five clinical S. epidermidis isolates demonstrated phenotypic variation, i.e. both black and red colonies on Congo Red agar. Black colonies displayed bi-modal electrophoretic mobility distributions at pH 2, but such phenotypic variation was absent in red colonies of the same strain as well as in control strains without phenotypic variation. All red colonies had lost ica and the ability to form biofilms, in contrast to black colonies of the same strain. Real time PCR targeting icaA indicated a reduction in gene copy number within cultures exhibiting phenotypic variation, which correlated with phenotypic variations in biofilm formation and electrophoretic mobility distribution of cells within a culture. Loss of ica was irreversible and independent of the mobile element IS256. Instead, in high frequency switching strains, spontaneous mutations in lexA were found which resulted in deregulation of recA expression, as shown by real time PCR. RecA is involved in genetic deletions and rearrangements and we postulate a model representing a new mechanism of phenotypic variation in clinical isolates of S. epidermidis. This is the first report of S. epidermidis strains irreversibly switching from biofilm-positive to biofilm-negative phenotype by spontaneous deletion of icaADBC.

Show MeSH
Related in: MedlinePlus