Inactivation of genes TEC1 and EFG1 in Candida albicans influences extracellular matrix composition and biofilm morphology

Background: Infections caused by Candida spp. have been associated with formation of a biofilm, i.e. a complex microstructure of cells adhering to a surface and embedded within an extracellular matrix (ECM). Methods: The ECMs of a wild-type (WT, SN425) and two Candida albicans mutant strains, Delta/Delta tec1 (CJN2330) and Delta/Delta efg1 (CJN2302), were evaluated. Colony-forming units (cfu), total biomass (mg), water-soluble polysaccharides (WSPs), alkali-soluble polysaccharides (ASPs), proteins (insoluble part of biofilms and matrix proteins), and extracellular DNA (eDNA) were quantified. Variable-pressure scanning electron microscopy and confocal scanning laser microscopy were performed. The biovolume (mu m(3)/mu m(2)) and maximum thickness (mu m) of the biofilms were quantified using COMSTAT2. Results: ASP content was highest in WT (mean +/- SD: 74.5 +/- 22.0 mu g), followed by Delta/Delta tec1 (44.0 +/- 24.1 mu g) and Delta/Delta efg1 (14.7 +/- 5.0 mu g). The protein correlated with ASPs (r = 0.666) and with matrix proteins (r = 0.670) in the WT strain. The population in Delta/Delta efg1 correlated with the protein (r = 0.734) and its biofilms exhibited the lowest biomass and biovolume, and maximum thickness. In Delta/Delta tec1, ASP correlated with eDNA (r = 0.678). Conclusion: ASP production may be linked to C. albicans cell filamentous morphology.