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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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Related in: MedlinePlus

Relative expression of recA. The relative expression of recA was plotted using RP62A as a control strain and gyrB as the reference gene. The 2−ΔΔCT was calculated from the average CT values of two reactions and standard deviations are given
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Fig5: Relative expression of recA. The relative expression of recA was plotted using RP62A as a control strain and gyrB as the reference gene. The 2−ΔΔCT was calculated from the average CT values of two reactions and standard deviations are given

Mentions: The effect of the mutations in lexA, as observed in S. epidermidis ATCC12228 and two of the clinical isolates, on recA expression was analyzed using real time PCR. Relative to the control strain, S. epidermidis RP62A, recA was over-expressed four times in S. epidermidis ATCC12228 (Fig. 5). Upon comparison of the other strains in this study, 196 and 906 showed significant over-expression of recA (4 and 12 times, respectively) compared to S. epidermidis RP62A.Fig. 5


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)

Relative expression of recA. The relative expression of recA was plotted using RP62A as a control strain and gyrB as the reference gene. The 2−ΔΔCT was calculated from the average CT values of two reactions and standard deviations are given
© Copyright Policy
Related In: Results  -  Collection

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

Fig5: Relative expression of recA. The relative expression of recA was plotted using RP62A as a control strain and gyrB as the reference gene. The 2−ΔΔCT was calculated from the average CT values of two reactions and standard deviations are given
Mentions: The effect of the mutations in lexA, as observed in S. epidermidis ATCC12228 and two of the clinical isolates, on recA expression was analyzed using real time PCR. Relative to the control strain, S. epidermidis RP62A, recA was over-expressed four times in S. epidermidis ATCC12228 (Fig. 5). Upon comparison of the other strains in this study, 196 and 906 showed significant over-expression of recA (4 and 12 times, respectively) compared to S. epidermidis RP62A.Fig. 5

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