Endolithic Fungal Species Markers for Harshest Conditions in the McMurdo Dry Valleys, Antarctica

Abstract

The microbial communities that inhabit lithic niches inside sandstone in the Antarctic McMurdo Dry Valleys of life’s limits on Earth. The cryptoendolithic communities survive in these ice-free areas that have the lowest temperatures on Earth coupled with strong thermal fluctuations, extreme aridity, oligotrophy and high levels of solar and UV radiation. In this study, based on DNA metabarcoding, targeting the fungal Internal Transcribed Spacer region 1 (ITS1) and multivariate statistical analyses, we supply the first comprehensive overview onto the fungal diversity and composition of these communities sampled over a broad geographic area of the Antarctic hyper-arid cold desert. Six locations with surfaces that experience variable sun exposure were sampled to compare communities from a common area across a gradient of environmental pressure. The Operational Taxonomic Units (OTUs) identified were primarily members of the Ascomycota phylum, comprised mostly of the Lecanoromycetes and Dothideomycetes classes. The fungal species Friedmanniomyces endolithicus, endemic to Antarctica, was found to be a marker species to the harshest conditions occurring in the shady, south exposed rock surfaces. Analysis of community composition showed that sun exposure was an environmental property that explained community diversity and structured endolithic colonization.

Beyond the extremes: Rocks as ultimate refuge for fungi in drylands

“…Although these genera belong to different families, they show a remarkable morphological similarity in their cryptoendolithic growth form. Moreover, authors found that lichens were more abundant in northern sunexposed rocks, and a few of them (Acarosporaceae, Caliciaceae, Catillariaceae, and Trapeliaceae) were identified as biomarker species for this condition (Coleine et al 2018a(Coleine et al , 2018b(Coleine et al , 2020d. These findings supported the hypothesis expressed many years earlier for both hot and cold deserts (Friedmann 1977(Friedmann , 1978Nash et al 1977).…”

“…In recent molecular-based surveys, targeting fungal internal transcribed spacer (ITS) region, Coleine and collaborators investigated the diversity and structure of the cryptoendolithic fungal community in sandstone samples collected along a gradient ranging from 1000 to 3300 m altitude. Authors found lichenized fungi prevailing in the northern sun-exposed surface, whereas black microcolonial fungi invariably predominated at the highest altitudes and southern expositions where conditions are much more extreme (Coleine et al 2018a(Coleine et al , 2018b(Coleine et al , 2020d. More recently, an untargeted metabolomics revealed specific responses and adaptations to sun exposure.…”

Uncovered Microbial Diversity in Antarctic Cryptoendolithic Communities Sampling Three Representative Locations of the Victoria Land

“…Several factors have been identified that may putatively influence Antarctic cryptoendolithic distributions, both abiotic (e.g., sun exposure, altitude) [17,18,41] and biotic (fungi-bacteria interaction) [19]. In this study, the impact of habitat has been investigated.…”

“…In particular, the endemic black fungus F. endolithicus represents the most widespread and frequently isolated from Antarctic endolithic communities, up to 3300 m a.s.l. [17,41], suggesting a high degree of adaptation and specialization to the prohibitive conditions of such environments. Recently, the whole genome of F. endolithicus CCFEE 5311 was sequenced and the genome size was 46.75 Mbp; genomic traits in response to salt, X-rays, cold and DNA damage stresses have been identified, confirming exceptional poly-extremo tolerance of this species to survive across a wide variety of stresses [58].…”

Microbial Communities in Permafrost Soils of Larsemann Hills, Eastern Antarctica: Environmental Controls and Effect of Human Impact

“…Many researchers indicated a significant diversity of microorganisms in Antarctic soils and rocks [1,[7][8][9]. Special attention has been given to investigation of cryptoendolithic systems to reveal fungal and bacterial community structure in harsh environments of different regions of Antarctica [10][11][12][13]. Previous studies of microbial communities in soils have been mainly conducted in the Transantarctic region of the Victoria Land, Antarctic Peninsula and surrounding Islands.…”