Relative Abundances of Candida albicans and Candida glabrata in Coculture Biofilms Impact Biofilm Structure and Formation.

is a member of the normal human microbiota and often resides on mucosal surfaces such as the oral cavity or the gastrointestinal tract. In addition to their commensality, species can opportunistically become pathogenic if the host microbiota is disrupted or if the host immune system becomes compromised. An important factor for pathogenesis is its ability to form biofilm communities. The two most medically important species- and -are often coisolated from infection sites, suggesting the importance of coculture biofilms. In this work, we report that biofilm formation of the coculture population depends on the relative ratio of starting cell concentrations of and When using a starting ratio of to of 1:3, ∼6.5- and ∼2.5-fold increases in biofilm biomass were observed relative to those of a monoculture and a / ratio of 1:1, respectively. Confocal microscopy analysis revealed the heterogeneity and complex structures composed of long hyphae and cell clusters in the coculture biofilms, and reverse transcription-quantitative PCR (qRT-PCR) studies showed increases in the relative expression of the and adhesion genes in the / 1:3 biofilm compared to that in the monoculture biofilm. Additionally, only the 1:3 / biofilm demonstrated an increased resistance to the antifungal drug caspofungin. Overall, the results suggest that interspecific interactions between these two fungal pathogens increase biofilm formation and virulence-related gene expression in a coculture composition-dependent manner. and are often coisolated during infection, and the occurrence of coisolation increases with increasing inflammation, suggesting possible synergistic interactions between the two species in pathogenesis. During the course of an infection, the prevalence of each species may change over time due to differences in metabolism and in the resistance of each species to antifungal therapies. Therefore, it is necessary to understand the dynamics between and in coculture to develop better therapeutic strategies against infections. Existing work has focused on understanding how an equal-part culture of and impacts biofilm formation and pathogenesis. What is not understood, and what is investigated in this work, is how the composition of species in coculture impacts overall biofilm formation, virulence gene expression, and the therapeutic treatment of biofilms.