Nutrient acquisition by pathogenic fungi: Nutrient availability, pathway regulation, and differences in substrate utilization

All pathogenic microorganisms have in common that they need to feed on nutrients available from their host. Therefore, the specific interruption of metabolic pathways is a promising approach which could lead to the discovery of new antimicrobial drugs. However, nutrient availability strongly varies in respect to the infected host niche and pathogens may possess different strategies to acquire nutrients. This review focuses on the differences in regulation and use of key metabolic pathways during infection by pathogenic fungi, especially in the filamentous fungus Aspergillus fumigatus and the dimorphic yeast Candida albicans. Besides universal metabolic pathways, emphasis is given on pathways, which are absent in humans and might, therefore, suit as antifungal drug targets. Niche-specific nutrient availability and different physiological strategies complicate the identification of metabolic pathways, which are essential for all pathogens at each step of the infection process.