Basidiomycetous Yeast, Glaciozyma antarctica, Forming Frost-Columnar Colonies on Frozen Medium

Seiichi Fujiu,Midori Yoshida,Yuichi Hanada,Sakae Kudoh,Eriko Kobayashi,Masanobu Ito,Tamotsu Hoshino

doi:10.3390/microorganisms9081679

Abstract

The basidiomycetous yeast, Glaciozyma antarctica, was isolated from various terrestrial materials collected from the Sôya coast, East Antarctica, and formed frost-columnar colonies on agar plates frozen at −1 °C. Thawed colonies were highly viscous, indicating that the yeast produced a large number of extracellular polysaccharides (EPS). G. antarctica was then cultured on frozen media containing red food coloring to observe the dynamics of solutes in unfrozen water; pigments accumulated in frozen yeast colonies, indicating that solutes were concentrated in unfrozen water of yeast colonies. Moreover, the yeast produced a small quantity of ice-binding proteins (IBPs) which inhibited ice crystal growth. Solutes in unfrozen water were considered to accumulate in the pore of frozen colonies. The extracellular IBPs may have held an unfrozen state of medium water after accumulation in the frost-columnar colony.

Highlights

Even in the continental Antarctic region, which represents one of the coldest places in the world, various eukaryotic microorganisms are known to exist
Our results indicated that G. antarctica had unique physiologic characteristics against freezing stress to adapt to continental Antarctica
We found that the basidiomycetous yeast, G. antarctica, produced a large amount of extracellular polysaccharides (EPS) and developed frost-columnar colonies on frozen PDA

Summary

Introduction

Even in the continental Antarctic region, which represents one of the coldest places in the world, various eukaryotic microorganisms are known to exist. Isolated basidiomycetous fungi in this region occurred in yeast-form except for alien species [1], and basidiomycetous yeasts were dominant among culturable fungal strains in the McMurdo. Tremellomycetes and Agaricomycetes (known species were filamentous form) were detected in soils near glacial lakes in the McMurdo Dry Valley [7] and Victoria Land [8]. By DNA metabarcording, and Tremellomycetes were the dominant taxa in these areas. We described that ecophysiological strategies for freezing tolerance of filamentous fungi differed among taxa in in the Northern Hemisphere [10]. Filamentous basidiomycetes such as Typhula ishikariensis secreted abundant ice-binding proteins (IBPs)

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Conclusion