Systematic screens of a Candida albicans homozygous deletion library decouple morphogenetic switching and pathogenicity

Abstract

Candida albicans is the most common cause of serious fungal disease in humans. Creation of isogenic null mutants of this diploid organism, which requires sequential gene targeting, allows dissection of virulence mechanisms. Published analyses of such mutants show a near-perfect correlation between C. albicans pathogenicity and the ability to undergo a yeast-to-hypha morphological switch in vitro. However, most studies used mutants constructed with a marker that is itself a virulence determinant and therefore complicates their interpretation. Using alternative markers, we created ~3000 homozygous deletion strains affecting 674 genes or roughly 11% of the C. albicans genome. Screening for infectivity in a mouse model and for morphological switching and cell proliferation in vitro, we identified 115 infectivity-attenuated mutants, of which nearly half demonstrated normal morphological switching and proliferation. Analysis of such mutants identified the glycolipid, glucosylceramide, as the first small molecule synthesized by this pathogen to be required specifically for virulence.

Chemical screening identifies filastatin, a small molecule inhibitor of Candida albicans adhesion, morphogenesis, and pathogenesis

“…For example, experiments with a doxycycline-inducible transcription factor (NRG1) that governs hyphae formation have shown that the ability to form hyphae is continually required for the lethality associated with systemic candidaisis (6). Likewise, many mutants defective in hyphae formation are nonpathogenic (7) and poor at biofilm formation, although this correlation is not absolute (38).…”

Candida biofilm formation on voice prostheses

“…albicans morphogenetic conversions (the reversible switching between yeast and filamentous forms) are important for multiple aspects of C. albicans biology, pathogenicity and biofilm development. Morphogenesis is considered a key virulence trait of the fungus, since strains locked in a given morphology exhibit attenuated virulence (Noble et al, 2010;Saville et al, 2003). Hyphal growth and the coordinated expression of hypha-specific genes are also important for virulence, as they promote attachment to biotic and abiotic surfaces (Fu et al, 2002;Nobile et al, 2008), tissue invasion (Gow et al, 2002) and escape from phagocytic immune cells (Lorenz et al, 2004).…”

A comprehensive functional portrait of two heat shock factor-type transcriptional regulators involved in Candida albicans morphogenesis and virulence

“…The success of C. albicans as a major fungal pathogen of humans relies on a number of pathogenic traits, among which its capacity to grow and switch between at least three distinctive morphological forms: budding yeast, pseudohyphae and hyphae [2][3][4][5]. The morphogenetic transition has been commonly described as a critical trait for survival and virulence in the host, even though the analysis of a wide array of C. albicans knock-out mutants suggests that pathogenesis can be dissociated to some extent from morphological switching [6][7][8].…”