Characterization of a novel polyextremotolerant fungus, Exophiala viscosa, with insights into its melanin regulation and ecological niche

Authors

Erin C. Carr, University of Nebraska-Lincoln
Quin Barton, University of Nebraska-Lincoln
Sarah Grambo, Iowa State University
Mitchell Sullivan, University of Nebraska-Lincoln
Cecile M. Renfro, University of Nebraska-Lincoln
Alan Kuo, Lawrence Berkeley National Laboratory
Jasmyn Pangilinan, Lawrence Berkeley National Laboratory
Anna Lipzen, Lawrence Berkeley National Laboratory
Keykhosrow Keymanesh, Lawrence Berkeley National Laboratory
Emily Savage, Lawrence Berkeley National Laboratory
Kerrie Barry, Lawrence Berkeley National Laboratory
Igor V. Grigoriev, Lawrence Berkeley National Laboratory, University of California Berkeley
Wayne R. Riekhof, University of Nebraska–LincolnFollow
Steven D. Harris, Iowa State University

Date of this Version

5-23-2023

Citation

G3, 2023, 13(8), jkad110. https://doi.org/10.1093/g3journal/jkad110

Comments

Open access.

Abstract

Black yeasts are polyextremotolerant fungi that contain high amounts of melanin in their cell wall and maintain a primar yeast form. These fungi grow in xeric, nutrient depletes environments which implies that they require highly flexible metabolisms and have been suggested to contain the ability to form lichen-like mutualisms with nearby algae and bacteria. However, the exact ecological niche and interactions between these fungi and their surrounding community are not well understood. We have isolated 2 novel black yeasts from the genus Exophiala that were recovered from dryland biological soil crusts. Despite notable differences in colony and cellular morphology, both fungi appear to be members of the same species, which has been named Exophiala viscosa (i.e. E. viscosa JF 03-3 Goopy and E. viscosa JF 03-4F Slimy). A combination of whole genome sequencing, phenotypic experiments, and melanin regulation experiments have been performed on these isolates to fully characterize these fungi and help decipher their fundamental niche within the biological soil crust consortium. Our results reveal that E. viscosa is capable of utilizing a wide variety of carbon and nitrogen sources potentially derived from symbiotic microbes, can withstand many forms of abiotic stresses, and excretes melanin which can potentially provide ultraviolet resistance to the biological soil crust community. Besides the identification of a novel species within the genus Exophiala, our study also provides new insight into the regulation of melanin production in polyextremotolerant fungi.