Carboxylic acid transportes Jen1 and Jen2 affect Candida albicans biofilms' formation and susceptibility to fluconazole

Candida spp. often inhabits niches that are glucose-limited but rich in alternative carbon sources (e.g. lactate, acetate), an ability that contributes to cells' virulence. In glucose-poor niches, Candida albicans cells express JEN1 and JEN2 genes encoding the carboxylic acids transporters Jen1 and Jen2, respectively, which have been reported to be important in the early stages of infection. In this work we showed that disruption of these carboxylic acids transporters genes alters susceptibility to fluconazole both in biofilm and planktonic cells and biofilm formation. We tested C. albicans cells' capacity for biofilm formation in RPMI medium at pH 7.0 and pH 5.0 (with or without lactic acid). We demonstrated that C. albicans forms more biofilm biomass at pH 5.0, with predominance of yeast cells, than at pH 7.0, where a hyphae network is present. In lactic acid containing medium, a higher amount of biofilm is formed in comparison to what is observed in RPMI, a medium that contains glucose 2 g/L (0.2%). At pH 7.0, jen1jen2 mutant strain displays a cell morphology similar with the wild type strain, however, in the presence of lactic acid, pH 5.0, there are almost no hyphae. The mutant strain displays a more compact biofilm with higher resistance to fluconazole than wild type biofilm. In the case of planktonic cells, the phenotype was exactly the opposite; the double mutant strain was more susceptible to fluconazole in lactic acid, at pH 5.0. These results show that, carboxylic acids transporters have an important role in biofilm formation and in the acquisition of resistance to antifungal drugs.This work was supported by the strategic programme UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI). Fluconazole was kindly provided by Pfizer®, S.A. in its pure compound form. The work on CEB was supported by Pest-OE/EQB/ LA0023/2013, from FCT, “BioHealth - Biotechnology and Bioengineering approaches to improve health quality", Ref. NORTE-07-0124-FEDER-000027, co-funded by the Programa Operacional Regional do Norte (ON.2 – O Novo Norte), QREN, FEDER and the project “Consolidating Research Expertise and Resources on Cellular and Molecular Biotechnology at CEB/IBB”, Ref. FCOMP-01-0124-FEDER-027462. We also would like to acknowledge the support of the European Research Council through the advanced grant “STRIFE” (C-2009-AdG-249793)