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

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

Highly heterogeneous mycobiota shape fungal diversity in two globally distributed lichens

Lichens are multi-kingdom symbioses in which fungi, algae and bacteria interact to develop a stable selection unit. In addition to the mycobiont forming the symbiosis, fungal communities associated with lichens represent the lichen mycobiota. Because lichen mycobiota diversity is still largely unknown, we aimed to characterize it in two cosmopolitan lichens, Rhizoplaca melanophthalma and Tephromela atra. The mycobiota were investigated across a broad distribution using both a culture-dependent approach and environmental DNA metabarcoding. The variation of the mycobiota associated with the two lichen species was extremely high, and a stable species-specific core mycobiota was not detected with the methods we applied. Most taxa were present in a low fraction of the samples, and no fungus was ubiquitously present in either lichen species. The mycobiota are thus composed of heterogeneous fungi, and some taxa are detectable only by culture-dependent approaches. We suspect that lichens act as niches in which these fungi may exploit thallus resources and only a few may establish more stable trophic relationships with the major symbiotic partners

Integrated eDNA metabarcoding and morphological analyses assess spatio-temporal patterns of airborne fungal spores

Fungi represent relevant allergens and plant pathogens that can disperse on long ranges, potentially producing severe consequences on public health and agriculture. Up to 11% of the bioaerosol particles are fungal spores and mycelium fragments. Estimation of fungal species diversity in time and space is decisive but may be biased by abiotic conditions and sampling methods. Traditional morphological analyses of fungal spores have been widely applied in aerobiology in the past, while recently eDNA metabarcoding can complement these studies. Here, we used both morphological analysis (spore count and taxon identification) and high-throughput sequencing to disentangle spatio-temporal variation of fungi across Northern and Central Italy and to evaluate the detection efficiency of the two approaches. Our results showed that eDNA metabarcoding detects about three times more genera and has a higher detection efficiency than the morphological analyses. However, the efficiency is high in both spore count and eDNA metabarcoding methods when the most abundant or the rarest genera are considered but it can substantially vary between the two approaches when moderately abundant genera are analyzed. Furthermore, morphological spore determination resulted in higher variance explained by PERMANOVA analysis with respect to eDNA metabarcoding (26% and 13%, respectively), which leads to a better spatio-temporal characterization of the fungal genera. As both morphological analyses and eDNA metabarcoding methods capture significant interactions between seasons and sites, they could be preferably used as complementing approaches to reliably study airborne fungal diversity and variation