Abstract
The black yeast Exophiala lecanii-corni of the order Chaetothyriales is notable for its ability to produce abundant quantities of DHN-melanin. While many other Exophiala species are frequent causal agents of human infection, E. lecanii-corni CBS 102400 lacks the thermotolerance requirements that enable pathogenicity, making it appealing for use in targeted functional studies and biotechnological applications. Here, we report the stress tolerance characteristics of E. lecanii-corni, with an emphasis on the influence of melanin on its resistance to various forms of stress. We find that E. lecanii-corni has a distinct stress tolerance profile that includes variation in resistance to temperature, osmotic, and oxidative stress relative to the extremophilic and pathogenic black yeast Exophiala dermatitidis. Notably, the presence of melanin substantially impacts stress resistance in E. lecanii-corni, while this was not found to be the case in E. dermatitidis. The cellular context, therefore, influences the role of melanin in stress protection. In addition, we present a detailed analysis of the E. lecanii-corni genome, revealing key differences in functional genetic content relative to other ascomycetous species, including a significant decrease in abundance of genes encoding ribosomal proteins. In all, this study provides insight into how genetics and physiology may underlie stress tolerance and enhances understanding of the genetic diversity of black yeasts.
Highlights
Black yeasts belonging to the ascomycete order Chaetothyriales have been of historic interest due to their frequent characterization as opportunistic pathogens [1]
Media screened included yeast peptone dextrose (YPD), yeast extract glucose (YEG), yeast extract sucrose (YES), malt peptone glucose (MPG), malt extract (MB), Czapek (CZ), Czapek yeast (CY), and glucose minimal media optimized for yeast (GMM)
The results revealed that E. lecanii-corni is substantially more susceptible to osmotic stress than E. dermatitidis, and that melanin contributes to osmoresistance in E. lecanii-corni
Summary
Black yeasts belonging to the ascomycete order Chaetothyriales have been of historic interest due to their frequent characterization as opportunistic pathogens [1]. These organisms, including those within the Exophiala genus, are distinguished by their abundant melanin content, thick cell walls, polymorphic growth, and ability to withstand a range of extreme conditions, including high and low temperatures, high salinity, desiccation, and various forms of non-ionizing and ionizing radiation [2,3,4,5]. E. lecanii-corni has garnered attention due to its demonstrated capacity to efficiently eliminate volatile organic compounds in vapor-phase, indicating its potential for bioremediation applications [8,9]. The genetic tractability of this organism has already been demonstrated [10], which paves the way for targeted functional studies, as well as genetic optimization of production yields for bioproducts of interest
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