Abstract
The human pathogen Candida albicans is considered an obligate commensal of animals, yet it is occasionally isolated from trees, shrubs, and grass. We generated genome sequence data for three strains of C. albicans that we isolated from oak trees in an ancient wood pasture, and compared these to the genomes of over 200 clinical strains. C. albicans strains from oak are similar to clinical C. albicans in that they are predominantly diploid and can become homozygous at the mating locus through whole-chromosome loss of heterozygosity. Oak strains differed from clinical strains in showing slightly higher levels of heterozygosity genome-wide. Using phylogenomic analyses and in silico chromosome painting, we show that each oak strain is more closely related to strains from humans and other animals than to strains from other oaks. The high genetic diversity of C. albicans from old oaks shows that they can live in this environment for extended periods of time.
Highlights
THE yeast Candida albicans is the most common yeast pathogen in humans (Barnett 2008), yet it is a commensal in most humans and inhabits a broad range of warmblooded animals (Barnett 2008)
Where multiple strains are considered, we show the mean, maximum, and minimum levels of genome-wide heterozygosity. b The length of genome sequence after excluding loss of heterozygosity (LOH) regions, known repeats, putatively repetitive regions, and centromeres. c The proportion of heterozygous sites in filtered regions. d Rows in bold show data summarized for all 3 oak strains and 180 clinical strains from Ropars et al (2018). e Clinical strains are less heterozygous than oak strains (Wilcoxon test, P 1⁄4 0:02). f Wilcoxon test, P 1⁄4 0:01: least 10 strains were available: clades 1, 2, 3, 4, 11, 13, and strains from unknown clades
We recently discovered C. albicans living on the bark of oak trees in a wood pasture in the New Forest (Table 1; Robinson et al 2016)
Summary
THE yeast Candida albicans is the most common yeast pathogen in humans (Barnett 2008), yet it is a commensal in most humans and inhabits a broad range of warmblooded animals (Barnett 2008). We generated genome sequences for three strains of C. albicans from oak bark from the New Forest in the United Kingdom (Robinson et al 2016) These are the first C. albicans genomes sequenced from a nonanimal source, and we compared them to the genomes of over 200 strains from humans and animals (Muzzey et al 2013; Hirakawa et al 2015; Ropars et al 2018). Albicans genomes sequenced from a nonanimal source, and we compared them to the genomes of over 200 strains from humans and animals (Muzzey et al 2013; Hirakawa et al 2015; Ropars et al 2018) They were collected from the same woodland, these oak strain genomes are genetically diverged from one another, and are more similar to diverged clinical lineages than they are to each other. C. albicans can live in the oak environment for prolonged periods
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