Genome structure and dynamics of the yeast pathogen Candida glabrata

Abstract

The yeast pathogen Candida glabrata is the second most frequent cause of Candida infections. However, from the phylogenetic point of view, C. glabrata is much closer to Saccharomyces cerevisiae than to Candida albicans. Apparently, this yeast has relatively recently changed its life style and become a successful opportunistic pathogen. Recently, several C. glabrata sister species, among them clinical and environmental isolates, have had their genomes characterized. Also, hundreds of C. glabrata clinical isolates have been characterized for their genomes. These isolates display enormous genomic plasticity. The number and size of chromosomes vary drastically, as well as intra- and interchromosomal segmental duplications occur frequently. The observed genome alterations could affect phenotypic properties and thus help to adapt to the highly variable and harsh habitats this yeast finds in different human patients and their tissues. Further genome sequencing of pathogenic isolates will provide a valuable tool to understand the mechanisms behind genome dynamics and help to elucidate the genes contributing to the virulence potential.

Keywords: Candida; chromosome polymorphism; genome rearrangements; pathogenic yeast; virulence genes.

Fig. 1

A schematics phylogenetic tree (adopted from Gabaldón et al., 2013) shows the Nakaseomyces species (marked with an asterisk) and some other yeasts. Candida glabrata, C. nivariensis, C. bracarensis are pathogenic fungi within the ‘glabrata group’. The whole-genome duplication event (WGD), which took place app. 100 million years ago, is arrowed.

Fig. 2

Candida glabrata yeast under electron microscope. The figure shows two single cells and two mother–daughter pairs during the budding process.

Fig. 3

Two possible mechanisms behind the birth of small chromosomes are shown (adapted from Ahmad et al., 2013). (1) The small chromosome (a) originated by segmental duplication within chromosome A. (2) Interchromosomal translocation, where a large segment of chromosome A is translocated to join the chromosome B leaving the rest of chromosome A as a small chromosome.