Sun Exposure Shapes Functional Grouping of Fungi in Cryptoendolithic Antarctic Communities.

Claudia Coleine,Laura Zucconi,Laura Selbmann,Silvano Onofri,Nuttapon Pombubpa,Jason Stajich

doi:10.3390/life8020019

Abstract

Antarctic cryptoendolithic microbial communities dominate ice-free areas of continental Antarctica, among the harshest environments on Earth. The endolithic lifestyle is a remarkable adaptation to the exceptional environmental extremes of this area, which is considered the closest terrestrial example to conditions on Mars. Recent efforts have attempted to elucidate composition of these extremely adapted communities, but the functionality of these microbes have remained unexplored. We have tested for interactions between measured environmental characteristics, fungal community membership, and inferred functional classification of the fungi present and found altitude and sun exposure were primary factors. Sandstone rocks were collected in Victoria Land, Antarctica along an altitudinal gradient from 834 to 3100 m a.s.l.; differently sun-exposed rocks were selected to test the influence of this parameter on endolithic settlement. Metabarcoding targeting the fungal internal transcribed spacer region 1 (ITS1) was used to catalogue the species found in these communities. Functional profile of guilds found in the samples was associated to species using FUNGuild and variation in functional groups compared across sunlight exposure and altitude. Results revealed clear dominance of lichenized and stress-tolerant fungi in endolithic communities. The main variations in composition and abundance of functional groups among sites correlated to sun exposure, but not to altitude.

Highlights

Fungi play essential roles in the function of terrestrial ecosystems as contributors to carbon and nitrogen cycles
(123 out of 449 OTUs total in dataset 1 and 119 out of 270 OTUs total), sequences of dataset 1 were grouped into 326 operational taxonomic units (OTUs), while 151 OTUs were retrieved in dataset 2
Ecological functions were assigned to 89 OTUs in dataset 1 and 110 OTUs in dataset 2

Summary

Introduction

Fungi play essential roles in the function of terrestrial ecosystems as contributors to carbon and nitrogen cycles. They can adopt a range of lifestyles, acting as saprotrophs, parasites, or symbionts (e.g., mycorrhizae, endophytes, and lichens), interacting with diverse breadth of organisms of all the biological kingdoms. In extreme conditions where relatively few organisms are able to survive, fungi can play important role in the recycling of organic matter and enabling nutrient uptake. Fungi, both filamentous and yeasts, dominate the eukaryotic composition of the highly oligotrophic soils of the Antarctic McMurdo Dry Valleys. The McMurdo Dry Valleys, the most similar environment available on Earth to the Martian surface, had been assumed to be practical sterile until a few decades ago, but has been found to support a limited number of living organisms [1,2,3,4]

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