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The MP65 gene is required for cell wall integrity, adherence to epithelial cells and biofilm formation in Candida albicans.

Sandini S, Stringaro A, Arancia S, Colone M, Mondello F, Murtas S, Girolamo A, Mastrangelo N, De Bernardis F - BMC Microbiol. (2011)

Bottom Line: Interestingly, the mp65Δ mutant displayed a marked reduction in adhesion to BEC and Caco-2 cells and severe defects in biofilm formation when compared to the wild type.All of the mentioned properties were totally or partially recovered in a revertant strain, demonstrating the specificity of gene deletion.We demonstrate that the MP65 gene of Candida albicans plays a significant role in maintaining cell wall integrity, as well as in adherence to epithelia and biofilm formation, which are major virulence attributes of this fungus.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Infectious, Parasitic and Immuno-mediated Diseases, Istituto Superiore di Sanità, Rome, 00161, Italy. silvia.sandini@iss.it

ABSTRACT

Background: The MP65 gene of Candida albicans (orf19.1779) encodes a putative β-glucanase mannoprotein of 65 kDa, which plays a main role in a host-fungus relationship, morphogenesis and pathogenicity. In this study, we performed an extensive analysis of a mp65Δ mutant to assess the role of this protein in cell wall integrity, adherence to epithelial cells and biofilm formation.

Results: The mp65Δ mutant showed a high sensitivity to a range of cell wall-perturbing and degrading agents, especially Congo red, which induced morphological changes such as swelling, clumping and formation of hyphae. The mp65Δ mutant showed an activation of two MAPKs (Mkc1p and Cek1p), a high level of expression of two stress-related genes (DDR48 and SOD5), and a modulated expression of β-glucan epitopes, but no gross changes in cell wall polysaccharide composition. Interestingly, the mp65Δ mutant displayed a marked reduction in adhesion to BEC and Caco-2 cells and severe defects in biofilm formation when compared to the wild type. All of the mentioned properties were totally or partially recovered in a revertant strain, demonstrating the specificity of gene deletion.

Conclusions: We demonstrate that the MP65 gene of Candida albicans plays a significant role in maintaining cell wall integrity, as well as in adherence to epithelia and biofilm formation, which are major virulence attributes of this fungus.

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Biofilm analysis of the mp65Δ mutant. (A) CV staining. Equal numbers of cells from the wild type (wt), mp65Δ mutant (hom) and revertant (rev) strains were suspended in 250 μl of RPMI medium and incubated in 24-well plates for 48 h at 37°C. Non-adherent cells were then removed by washing, and adherent cells were stained with CV. The biofilms were visualized before (Panel 1) and after (Panel 2) staining and then captured by using either a Gel Doc system (Bio-Rad), or using an inverted microscope at 40x magnification (Panel 3). (B) XTT assay. The colorimetric XTT assay, which determines the metabolic activity of the cells, was used to quantify the biofilms of the wild type (wt: grey column), mp65Δ mutant (hom: white column) and revertant (rev: black column) strains. Each result is the mean of 3 independent experiments (P≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom vs. wt and rev strains; error bars represent standard deviations). (C) Dry weight determination. The dry weight determination, which measures the total biomass of the cells, was used to quantify the biofilms of the wild type (wt: black column), mp65Δ mutant (hom: grey column) and revertant (rev: white column) strains. Results were normalized to wt, which was taken as 100%. Each result is the mean of 3 independent experiments (P ≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom versus wt and rev strains; error bars represent standard deviations.
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Figure 6: Biofilm analysis of the mp65Δ mutant. (A) CV staining. Equal numbers of cells from the wild type (wt), mp65Δ mutant (hom) and revertant (rev) strains were suspended in 250 μl of RPMI medium and incubated in 24-well plates for 48 h at 37°C. Non-adherent cells were then removed by washing, and adherent cells were stained with CV. The biofilms were visualized before (Panel 1) and after (Panel 2) staining and then captured by using either a Gel Doc system (Bio-Rad), or using an inverted microscope at 40x magnification (Panel 3). (B) XTT assay. The colorimetric XTT assay, which determines the metabolic activity of the cells, was used to quantify the biofilms of the wild type (wt: grey column), mp65Δ mutant (hom: white column) and revertant (rev: black column) strains. Each result is the mean of 3 independent experiments (P≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom vs. wt and rev strains; error bars represent standard deviations). (C) Dry weight determination. The dry weight determination, which measures the total biomass of the cells, was used to quantify the biofilms of the wild type (wt: black column), mp65Δ mutant (hom: grey column) and revertant (rev: white column) strains. Results were normalized to wt, which was taken as 100%. Each result is the mean of 3 independent experiments (P ≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom versus wt and rev strains; error bars represent standard deviations.

Mentions: To determine the effects of the absence of the MP65 gene on biofilm formation, we performed two quantitative in vitro assays (dry weight and XTT), which characterize total and living biomass, respectively. As shown in Figures 6 B and 6C, the mp65Δ mutant displayed a severe defect in biofilm formation compared to the wild type strain, and the introduction of a single wild type MP65 allele in the revertant strain substantially salvaged the defect. These results were confirmed by observation of the biofilms before and after staining with CV, a semi-quantitative colorimetric assay that does not differentiate between live and dead cells (Figure 6A). Similar results were obtained when the biofilms were grown in spider medium (Additional file 1, Figure S1 and other data not shown).


The MP65 gene is required for cell wall integrity, adherence to epithelial cells and biofilm formation in Candida albicans.

Sandini S, Stringaro A, Arancia S, Colone M, Mondello F, Murtas S, Girolamo A, Mastrangelo N, De Bernardis F - BMC Microbiol. (2011)

Biofilm analysis of the mp65Δ mutant. (A) CV staining. Equal numbers of cells from the wild type (wt), mp65Δ mutant (hom) and revertant (rev) strains were suspended in 250 μl of RPMI medium and incubated in 24-well plates for 48 h at 37°C. Non-adherent cells were then removed by washing, and adherent cells were stained with CV. The biofilms were visualized before (Panel 1) and after (Panel 2) staining and then captured by using either a Gel Doc system (Bio-Rad), or using an inverted microscope at 40x magnification (Panel 3). (B) XTT assay. The colorimetric XTT assay, which determines the metabolic activity of the cells, was used to quantify the biofilms of the wild type (wt: grey column), mp65Δ mutant (hom: white column) and revertant (rev: black column) strains. Each result is the mean of 3 independent experiments (P≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom vs. wt and rev strains; error bars represent standard deviations). (C) Dry weight determination. The dry weight determination, which measures the total biomass of the cells, was used to quantify the biofilms of the wild type (wt: black column), mp65Δ mutant (hom: grey column) and revertant (rev: white column) strains. Results were normalized to wt, which was taken as 100%. Each result is the mean of 3 independent experiments (P ≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom versus wt and rev strains; error bars represent standard deviations.
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Figure 6: Biofilm analysis of the mp65Δ mutant. (A) CV staining. Equal numbers of cells from the wild type (wt), mp65Δ mutant (hom) and revertant (rev) strains were suspended in 250 μl of RPMI medium and incubated in 24-well plates for 48 h at 37°C. Non-adherent cells were then removed by washing, and adherent cells were stained with CV. The biofilms were visualized before (Panel 1) and after (Panel 2) staining and then captured by using either a Gel Doc system (Bio-Rad), or using an inverted microscope at 40x magnification (Panel 3). (B) XTT assay. The colorimetric XTT assay, which determines the metabolic activity of the cells, was used to quantify the biofilms of the wild type (wt: grey column), mp65Δ mutant (hom: white column) and revertant (rev: black column) strains. Each result is the mean of 3 independent experiments (P≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom vs. wt and rev strains; error bars represent standard deviations). (C) Dry weight determination. The dry weight determination, which measures the total biomass of the cells, was used to quantify the biofilms of the wild type (wt: black column), mp65Δ mutant (hom: grey column) and revertant (rev: white column) strains. Results were normalized to wt, which was taken as 100%. Each result is the mean of 3 independent experiments (P ≤ 0.05, Student's t-test, two-tailed, for comparison of dry weight of hom versus wt and rev strains; error bars represent standard deviations.
Mentions: To determine the effects of the absence of the MP65 gene on biofilm formation, we performed two quantitative in vitro assays (dry weight and XTT), which characterize total and living biomass, respectively. As shown in Figures 6 B and 6C, the mp65Δ mutant displayed a severe defect in biofilm formation compared to the wild type strain, and the introduction of a single wild type MP65 allele in the revertant strain substantially salvaged the defect. These results were confirmed by observation of the biofilms before and after staining with CV, a semi-quantitative colorimetric assay that does not differentiate between live and dead cells (Figure 6A). Similar results were obtained when the biofilms were grown in spider medium (Additional file 1, Figure S1 and other data not shown).

Bottom Line: Interestingly, the mp65Δ mutant displayed a marked reduction in adhesion to BEC and Caco-2 cells and severe defects in biofilm formation when compared to the wild type.All of the mentioned properties were totally or partially recovered in a revertant strain, demonstrating the specificity of gene deletion.We demonstrate that the MP65 gene of Candida albicans plays a significant role in maintaining cell wall integrity, as well as in adherence to epithelia and biofilm formation, which are major virulence attributes of this fungus.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Infectious, Parasitic and Immuno-mediated Diseases, Istituto Superiore di Sanità, Rome, 00161, Italy. silvia.sandini@iss.it

ABSTRACT

Background: The MP65 gene of Candida albicans (orf19.1779) encodes a putative β-glucanase mannoprotein of 65 kDa, which plays a main role in a host-fungus relationship, morphogenesis and pathogenicity. In this study, we performed an extensive analysis of a mp65Δ mutant to assess the role of this protein in cell wall integrity, adherence to epithelial cells and biofilm formation.

Results: The mp65Δ mutant showed a high sensitivity to a range of cell wall-perturbing and degrading agents, especially Congo red, which induced morphological changes such as swelling, clumping and formation of hyphae. The mp65Δ mutant showed an activation of two MAPKs (Mkc1p and Cek1p), a high level of expression of two stress-related genes (DDR48 and SOD5), and a modulated expression of β-glucan epitopes, but no gross changes in cell wall polysaccharide composition. Interestingly, the mp65Δ mutant displayed a marked reduction in adhesion to BEC and Caco-2 cells and severe defects in biofilm formation when compared to the wild type. All of the mentioned properties were totally or partially recovered in a revertant strain, demonstrating the specificity of gene deletion.

Conclusions: We demonstrate that the MP65 gene of Candida albicans plays a significant role in maintaining cell wall integrity, as well as in adherence to epithelia and biofilm formation, which are major virulence attributes of this fungus.

Show MeSH
Related in: MedlinePlus