Metabarcoding of Antarctic Lichens from Areas with Different Deglaciation Times Reveals a High Diversity of Lichen-Associated Communities

Lichens have developed numerous adaptations to optimise their survival under harsh abiotic stress, colonise different substrates, and reach substantial population sizes and high coverage in ice-free Antarctic areas, benefiting from a symbiotic lifestyle. As lichen thalli represent consortia with an unknown number of participants, it is important to know about the accessory organisms and their relationships with various environmental conditions. To this end, we analysed lichen-associated communities from Himantormia lugubris, Placopsis antarctica, P. contortuplicata, and Ramalina terebrata, collected from soils with differing deglaciation times, using a metabarcoding approach. In general, many more Ascomycete taxa are associated with the investigated lichens compared to Basidiomycota. Given our sampling, a consistently higher number of lichen-associated eukaryotes are estimated to be present in areas with deglaciation times of longer than 5000 years compared to more recently deglaciated areas. Thus far, members of Dothideomycetes, Leotiomycetes, and Arthoniomycetes have been restricted to the Placopsis specimens from areas with deglaciation times longer than 5000 years. Striking differences between the associated organisms of R. terebrata and H. lugubris have also been discovered. Thus, a species-specific basidiomycete, Tremella, was revealed for R. terebrata, as was a member of Capnodiales for H. lugubris. Our study provides further understanding of the complex terricolous lichen-associated mycobiome using the metabarcoding approach. It also illustrates the necessity to extend our knowledge of complex lichen symbiosis and further improve the coverage of microbial eukaryotes in DNA barcode libraries, including more extended sampling.

UHPLC-MS Metabolomic Fingerprinting, Antioxidant, and Enzyme Inhibition Activities of Himantormia lugubris from Antarctica

Himantormia lugubris is a Chilean native small lichen shrub growing in the Antarctica region. In this study, the metabolite fingerprinting and the antioxidant and enzyme inhibitory potential from this species and its four major isolated compounds were investigated for the first time. Using ultra-high performance liquid chromatography coupled to quadrupole-Orbitrap mass spectrometry analysis (UHPLC-Q-Orbitrap-MS), several metabolites were identified including specific compounds as chemotaxonomical markers, while major metabolites were quantified in this species. A good inhibition activity against cholinesterase (acetylcholinesterase (AChE) IC₅₀: 12.38 ± 0.09 µg/mL, butyrylcholinesterase (BChE) IC₅₀: 31.54 ± 0.20 µg/mL) and tyrosinase (22.32 ± 0.21 µg/mL) enzymes of the alcoholic extract and the main compounds (IC₅₀: 28.82 ± 0.10 µg/mL, 36.43 ± 0.08 µg/mL, and 7.25 ± 0.18 µg/mL, respectively, for the most active phenolic atranol) was found. The extract showed a total phenolic content of 47.4 + 0.0 mg of gallic acid equivalents/g. In addition, antioxidant activity was assessed using bleaching of DPPH and ORAC (IC₅₀: 75.3 ± 0.02 µg/mL and 32.7 ± 0.7 μmol Trolox/g lichen, respectively) and FRAP (27.8 ± 0.0 μmol Trolox equivalent/g) experiments. The findings suggest that H. lugubris is a rich source of bioactive compounds with potentiality in the prevention of neurodegenerative or noncommunicable chronic diseases.