Extracellular DNA release acts as an antifungal resistance mechanism in mature Aspergillus fumigatus biofilms.

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Extracellular DNA release acts as an antifungal resistance mechanism in mature Aspergillus fumigatus biofilms.

Eukaryot Cell. 2013 Jan 11;

Authors: Rajendran R, Williams C, Lappin DF, Millington O, Martins M, Ramage G

Abstract
Aspergillus fumigatus has been shown to form biofilms that are associated with adaptive antifungal resistance mechanisms. These include multi-drug efflux pumps, heat-shock proteins and extracellular matrix (ECM). ECM is a key structural and protective component of microbial biofilms, which in bacteria has been shown to contain extracellular DNA (eDNA). We therefore hypothesised that A. fumigatus biofilms also possess eDNA as part of the ECM, conferring a functional role. Fluorescence microscopy and quantitative PCR analyses demonstrated the presence of eDNA, which was released phase dependently (8<12<24<48 h). Random amplification of polymorphic DNA (RAPD) PCR showed that eDNA was identical to genomic DNA. Biofilm architectural integrity was destabilised by DNase treatment. Biochemical and transcriptional analysis showed that chitinase activity and mRNA levels of chitinase, a marker of autolysis, were significantly upregulated as the biofilm matured, and that inhibiting chitinases affected biofilm growth and stability, indicating mechanistically that autolysis was possibly involved. Finally, using checkerboard assays it was shown that combinational treatment of biofilms with DNase with amphotericin B and caspofungin significantly improved antifungal susceptibility. Collectively these data show that eDNA is an important structural component of A. fumigatus ECM, released through autolysis, which is important for protection from environmental stresses, including antifungal therapy.

PMID: 23314962 [PubMed - as supplied by publisher]