Life on top: cryptoendolithic ascomycetes and microalgae isolated from over 6000 m altitude

Abstract

Rocks are among the oldest terrestrial niches hosting a multiplicity of life forms, of which diversity has been only partially uncovered. Endolithic metacommunities comprise all major groups of microorganisms, such as chemo-organotrophic, chemo-lithotrophic and phototrophic, represented by bacteria, microalgae and microfungi. Their diversity is often difficult to describe and may remain underestimated. Furthermore, knowledge about the diversity of microorganisms colonizing rocks in peculiar niches is even poorer due to the difficulty to retrieve environmental specimens. Here, we report the phylogenetic and phenotypic characterization of a few endolithic fungi and algae isolated from rock fragments collected at high elevation, i.e., on the top of two mountains over 6000 m altitude, Muztagh Ata (China) and Cerro Mercendario (Argentina). The identity of the strains was confirmed by sequencing the nuclear ITS and LSU, the plastidial rbcL loci and by morphological analysis. Three fungal strains belonging to the class Dothideomycetes and one algal strain belonging to the genus Trebouxia were isolated from Muztagh Ata, while six fungal strains belonging to the order Chaetothyriales and four algal strains belonging to the genus Myrmecia were isolated from Cerro Mercedario. The detected species diversity is discussed in an evolutionary and ecological context.

Myrmecia, Not Asterochloris, Is the Main Photobiont of Cladonia subturgida (Cladoniaceae, Lecanoromycetes)

“…In general, Myrmecia has been found associated with terricolous lichen species, a habitat also shared by C. subturgida. The presence of free-living Myrmecia in the soils of regions with extreme climates, such as the Namib Desert [80] or high mountain ecosystems [57,81], has led to the hypothesis that this genus is well adapted to extreme arid conditions [57]. Although the conditions under which C. subturgida thrives are not so extreme, its climatic optimum is in areas with low rainfall and prolonged summer drought [47].…”

“…The selection of GenBank sequences was based on the BLAST searches. Most of them were generated by [44,[55][56][57]. Three ITS sequences of Lobosphaera incisa [58], Trebouxia lynnae [59], and Vulcanochloris guanchorum [10] were used as outgroups.…”

Fungal–Algal Association Drives Lichens’ Mutualistic Symbiosis: A Case Study with Trebouxia-Related Lichens

“…Scale in 0.02 substitutions per site. Figure S3: Phylogeny of lichen-forming algae Trebouxia species based on the Randomized Axelerated Maximum Likelihood (RAxML) analysis of a concatenated two-locus dataset including internal transcribed spacer region (ITS) and chloroplast ribulose-bisphosphate carboxylase-RuBisCO (rbcL) gene sequences, with reference sequences from the studies of [5,[93][94][95][96] marked in black. The number in each node represents bootstrap support (BS).…”