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. 2010 May;169(5):323-31.
doi: 10.1007/s11046-009-9264-y. Epub 2009 Dec 13.

Presence of extracellular DNA in the Candida albicans biofilm matrix and its contribution to biofilms

Margarida Martins  1 , Priya Uppuluri, Derek P Thomas, Ian A Cleary, Mariana Henriques, José L Lopez-Ribot, Rosário Oliveira
Affiliations

Presence of extracellular DNA in the Candida albicans biofilm matrix and its contribution to biofilms

Margarida Martins et al. Mycopathologia. 2010 May.

Abstract

DNA has been described as a structural component of the extracellular matrix (ECM) in bacterial biofilms. In Candida albicans, there is a scarce knowledge concerning the contribution of extracellular DNA (eDNA) to biofilm matrix and overall structure. This work examined the presence and quantified the amount of eDNA in C. albicans biofilm ECM and the effect of DNase treatment and the addition of exogenous DNA on C. albicans biofilm development as indicators of a role for eDNA in biofilm development. We were able to detect the accumulation of eDNA in biofilm ECM extracted from C. albicans biofilms formed under conditions of flow, although the quantity of eDNA detected differed according to growth conditions, in particular with regards to the medium used to grow the biofilms. Experiments with C. albicans biofilms formed statically using a microtiter plate model indicated that the addition of exogenous DNA (>160 ng/ml) increases biofilm biomass and, conversely, DNase treatment (>0.03 mg/ml) decreases biofilm biomass at later time points of biofilm development. We present evidence for the role of eDNA in C. albicans biofilm structure and formation, consistent with eDNA being a key element of the ECM in mature C. albicans biofilms and playing a predominant role in biofilm structural integrity and maintenance.

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Figures

Fig. 1
Fig. 1
Effect of DNase treatment on C. albicans biofilm formation. DifferentDNase concentrations (0, 0.02, 0.03, 0.06, 0.13, 0.25, 0.50, 1.00 and 2.00 mg/ml) were added to C. albicans cells at different times (0, 1, 2 and 24 h) post-inoculation in the wells of microtiter plates and incubated at 37°C under static conditions. The extent of biofilm formation was estimated by the crystal violet assay. Presented values are mean A550 ± standard error of mean of four independent experiments with three to eight replicates. Statistically significant differences (compared to biofilms formed in the absence of DNase) are indicated with an asterisk. (*, P < 0.05).
Fig. 2
Fig. 2
Example of microscopy evaluation of the effect of DNase treatment on 24 h C.albicans biofilm formation. Microphotographs of cells in wells before (I) and after (II) aspiration of medium and subsequent washings with PBS and crystal violet staining for biofilms treated with 0 mg/ml (a and c) and 0.13 mg/ml of DNase (b and d). The bar in the picture represents 200 μm.
Fig. 3
Fig. 3
Effect of addition of exogenous DNA on C. albicans biofilm formation. Different eDNA concentrations (0, 20, 40, 80, 160, 320, 640, 1280 and 2560 ng/ml) were added to C. albicans cells at different times (0, 1, 2 and 24 h) post -inoculation in the wells of microtiter plates and incubated at 37°C under static conditions. The extent of biofilm formation was estimated by the crystal violet assay. Presented values are mean A550 ± standard error of mean of four independent experiments with three to eight replicates. Statistically significant differences (compared to biofilms formed in the absence of DNA) are indicated with an asterisk. (*, P < 0.05).
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