title: Extracellular DNA release acts as an antifungal resistance mechanism in mature Aspergillus fumigatus biofilms.
abstract: Aspergillus fumigatus has been shown to form biofilms that are associated with adaptive antifungal resistance mechanisms. These include multidrug efflux pumps, heat shock proteins, and extracellular matrix (ECM). ECM is a key structural and protective component of microbial biofilms and in bacteria has been shown to contain extracellular DNA (eDNA). We therefore hypothesized 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 destabilized by DNase treatment. Biochemical and transcriptional analyses showed that chitinase activity and mRNA levels of chitinase, a marker of autolysis, were significantly upregulated as the biofilm matured and that inhibition of 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 plus amphotericin B and caspofungin significantly improved antifungal susceptibility. Collectively, these data show that eDNA is an important structural component of A. fumigatus ECM that is released through autolysis, which is important for protection from environmental stresses, including antifungal therapy.
authors: School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
authors: Ranjith
authors: R
authors: Rajendran
authors: Craig
authors: C
authors: Williams
authors: David F
authors: DF
authors: Lappin
authors: Owain
authors: O
authors: Millington
authors: Margarida
authors: M
authors: Martins
authors: Gordon
authors: G
authors: Ramage
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D001232:Aspergillus fumigatus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001329:Autolysis; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D000077336:Caspofungin; D002688:Chitinases / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000494:pharmacology; D025141:Drug Resistance, Fungal; D054714:Echinocandins / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism*; D016681:Genome, Fungal; D055666:Lipopeptides; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D000935:Antifungal Agents; D004271:DNA, Fungal; D054714:Echinocandins; D055666:Lipopeptides; D000666:Amphotericin B; D003851:Deoxyribonucleases; D002688:Chitinases; D000077336:Caspofungin