Distribution of mutations distinguishing the most prevalent disease-causing Candida albicans genotype from other genotypes

Abstract

Candida albicans is a major opportunistic pathogen of humans. Previous work has demonstrated the existence of a general-purpose genotype (GPG; equivalent to clade 1 as defined by multi-locus sequence typing data) that is more frequent than other genotypes as an agent of human disease and commensal colonization. We undertook a genomic screen which indicated that a large number of mutations differentiate GPG strains from other strains and that such mutations are scattered throughout the genome. GPG-specific mutations are non-synonymous more frequently than expected by chance, and are not randomly distributed across functional and structural gene categories. Our analysis has identified three categories of genes in which GPG-specific mutations are over-represented, namely genes for which expression changes during the yeast-hyphal transition, genes for which expression changes as a result of exposure to antifungal agents and repeat-containing ORFs. Although we have no direct evidence that the individual polymorphisms identified confer selective advantages to GPG strains, the results support our contention that the high prevalence of GPG strains is not merely due to genetic drift but that GPG strains have reached a high prevalence because they possess a multitude of fitness-enhancing traits. They also indicate that the distribution of genes marked by GPG-specific mutations across functional and structural categories could identify physiological traits that are of particular importance to the success of GPG strains in their interactions with the human host.