The Role of Isocitrate Lyase (ICL1) in the Metabolic Adaptation of Biofilms.

BACKGROUND

A major characteristic of biofilm cells that differentiates them from free-floating cells is their high tolerance to antifungal drugs. This high resistance is attributed to particular biofilm properties, including the accumulation of extrapolymeric substances, morphogenetic switching, and metabolic flexibility.

OBJECTIVES

This study evaluated the roles of metabolic processes (in particular the glyoxylate cycle) on biofilm formation, antifungal drug resistance, morphology, and cell wall components.

METHODS

Growth, adhesion, biofilm formation, and cell wall carbohydrate composition were quantified for isogenic ICL1/ICL1, ICL1/, and / strains. The morphology and topography of these strains were compared by light microscopy and scanning electron microscopy. (glucan synthase), (14-α-demethylase), and (efflux pump) mRNA levels were quantified using qRT-PCR.

RESULTS

The ICL1/icl1 and / strains formed similar biofilms and exhibited analogous drug-tolerance levels to the control ICL1/ICL1 strains. Furthermore, the drug sequestration ability of β-1, 3-glucan, a major carbohydrate component of the extracellular matrix, was not impaired. However, the inactivation of ICL1 did impair morphogenesis. ICL1 deletion also had a considerable effect on the expression of the , , and genes. and were upregulated in ICL1/ and / cells throughout the biofilm developmental stages, and was upregulated at the early phase. However, their expression was downregulated compared to the control ICL1/ICL1 strain.

CONCLUSIONS

We conclude that the glyoxylate cycle is not a specific determinant of biofilm drug resistance.