FBP1 and infection: Indeed, C. albicans virulence in vivo requires Icl1, Pck1, Fbp1, and Pyk1, all of which are involved in competing carbon metabolism pathways (25, 28, –, 30), reflecting the different forms of nutrient metabolism associated with different intracellular and extracellular environments in the host and explaining why infections with cultured macrophages often do not translate into the same in vivo phenotypes.