title: Extracellular DNA release confers heterogeneity in Candida albicans biofilm formation.
abstract: BACKGROUND
  Biofilm formation by Candida albicans has shown to be highly variable and is directly associated with pathogenicity and poor clinical outcomes in patients at risk. The aim of this study was to test the hypotheses that the extracellular DNA release by C. albicans is strain dependent and is associated with biofilm heterogeneity.
  
  
  RESULTS
  Initially, biofilm formed by C. albicans high biofilm formers (HBF) or low biofilm formers (LBF) were treated with DNase to find whether eDNA play a role in their biofilm formation. Digestion of biofilm eDNA significantly reduced the HBF biofilm biomass by five fold compared to untreated controls. In addition, quantification of eDNA over the period of biofilm formation by SYBR green assay demonstrate a significantly higher level of 2 to 6 fold in HBF compared to LBF. Biochemical and transcriptional analyses showed that chitinase activity and mRNA levels of chitinase genes, a marker of autolysis, were upregulated in 24 h biofilm formation by HBF compared to LBF, indicating autolysis pathway possibly involved in causing variation. The biofilm biomass and eDNA release by single (∆cht2, ∆cht3) and double knockout (∆cht2/∆cht3) chitinase mutants were significantly less compared to their parental strain CA14, confirming the role of chitinases in eDNA release and biofilm formation. Correlation analysis found a positive correlation between chitinases and HWP1, suggesting eDNA may release during the hyphal growth. Finally, we showed a combinational treatment of biofilms with DNase or chitinase inhibitor (acetazolamide) plus amphotericin B significantly improved antifungal susceptibility by 2 to 8 fold.
  
  
  CONCLUSIONS
  Collectively, these data show that eDNA release by C. albicans clinical isolates is variable and is associated with differential biofilm formation. Digestion of biofilm eDNA by DNase may provide a novel therapeutic strategies to destabilise biofilm growth and improves antifungal sensitivity.
authors.affiliation: Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, 378 Sauchiehall Street, Glasgow, G2 3JZ, UK. Ranjith.Rajendran@glasgow.ac.uk.
authors.forename: Ranjith
authors.initials: R
authors.lastname: Rajendran
authors.affiliation: Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, 378 Sauchiehall Street, Glasgow, G2 3JZ, UK. leighann.sherry@glasgow.ac.uk.
authors.forename: Leighann
authors.initials: L
authors.lastname: Sherry
authors.affiliation: Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, 378 Sauchiehall Street, Glasgow, G2 3JZ, UK. David.Lappin@glasgow.ac.uk.
authors.forename: David F
authors.initials: DF
authors.lastname: Lappin
authors.affiliation: Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, 378 Sauchiehall Street, Glasgow, G2 3JZ, UK. Christopher.Nile@glasgow.ac.uk.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Nile
authors.affiliation: Institute of Healthcare Associated Infection, School of Health, Nursing and Midwifery, University of the West of Scotland, Paisley, UK. karen.smith@uws.ac.uk.
authors.forename: Karen
authors.initials: K
authors.lastname: Smith
authors.affiliation: Institute of Healthcare Associated Infection, School of Health, Nursing and Midwifery, University of the West of Scotland, Paisley, UK. Craig.Williams@uws.ac.uk.
authors.forename: Craig
authors.initials: C
authors.lastname: Williams
authors.affiliation: Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, AB25 2ZD, UK. c.a.munro@abdn.ac.uk.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Munro
authors.affiliation: Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, 378 Sauchiehall Street, Glasgow, G2 3JZ, UK. gordon.ramage@glasgow.ac.uk.
authors.forename: Gordon
authors.initials: G
authors.lastname: Ramage
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002176:Candida albicans / Q000235:genetics / Q000502:physiology*; D002688:Chitinases / Q000096:biosynthesis / Q000235:genetics; D004271:DNA, Fungal / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D012333:RNA, Messenger / Q000032:analysis
chemical_list: D004271:DNA, Fungal; D012333:RNA, Messenger; D002688:Chitinases