<i>Cryptococcus neoformans</i> adapts to host CO ₂ concentrations through the coordinated remodeling of central carbon metabolism, oxidative stress resistance, and membrane homeostasis

<i>Cryptococcus neoformans</i> is an environmental pathogen that remodels its cellular physiology to survive within mammals and, in susceptible hosts, cause life-threatening meningoencephalitis. Of the many distinctions between the external environment and mammalian tissues, CO₂ concentration in the host is 2 orders of magnitude higher than in the environment and represent a critical stress for <i>C. neoformans</i>. <i>C. neoformans</i> strains that do not replicate at host CO₂ concentrations are less virulent in mouse models of infection, further supporting CO₂ tolerance as a virulence trait. To further understand the genetic determinants of <i>C. neoformans</i> CO₂ tolerance, we performed a near genome-wide screen for deletion mutants with altered CO₂ fitness using a competitive growth assay. A total of 301 of 4698 deletion mutants showed altered CO₂ tolerance (245 reduced fitness; 51 increased fitness) demonstrating the global effect of host CO₂ on <i>C. neoformans</i> physiology. Based on this data set as well as a metabolomic analysis of <i>C. neoformans</i> adaptation to host CO₂, we show that remodeling of central carbon metabolism, oxidative stress buffering and membrane homeostasis represent an integrated response to CO₂ stress that is mediated in part by the TOR-Ypk1 signaling axis. We propose that CO₂-induced capsule formation leads to reduced cellular glucose which, in turn, triggers remodeling of central carbon metabolism toward utilization of alternative carbon sources and increased mitochondrial respiration/reactive oxygen generation. Thus, these data provide a near genome-wide profile of the genetic determinants <i>of C. neoformans</i> CO₂ tolerance as well as a model for how this important environmental human fungal pathogen alters its physiology to proliferate in the host.