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Background and Methods: We assessed the prokaryotic and eukaryotic diversity present in non-vegetated and vegetated soils on King George Island, Maritime Antarctic, in combination with measurements of carbon dioxide fluxes. Results: For prokaryotes, 381 amplicon sequence variants (ASVs) were assigned, dominated by the phyla Actinobacteriota, Acidobacteriota, Pseudomonadota, Chloroflexota, and Verrucomicrobiota. A total of 432 eukaryotic ASVs were assigned, including representatives from seven kingdoms and 21 phyla. Fungi dominated the eukaryotic communities, followed by Viridiplantae. Non-vegetated soils had higher diversity indices compared with vegetated soils. The dominant prokaryotic ASV in non-vegetated soils was Pyrinomonadaceae sp., while Pseudarthrobacter sp. dominated vegetated soils. Mortierella antarctica (Fungi) and Meyerella sp. (Viridiplantae) were dominant eukaryotic taxa in the non-vegetated soils, while Lachnum sp. (Fungi) and Polytrichaceae sp. (Viridiplantae) were dominant in the vegetated soils. Measured CO₂ fluxes indicated that the net ecosystem exchange values measured in vegetated soils were lower than ecosystem respiration in non-vegetated soils. However, the total flux values indicated that the region displayed positive ecosystem respiration values, suggesting that the soils may represent a source of CO₂ in the atmosphere. Conclusions: Our study revealed the presence of rich and complex communities of prokaryotic and eukaryotic organisms in both soil types. Although non-vegetated soils demonstrated the highest levels of diversity, they had lower CO₂ fluxes than vegetated soils, likely reflecting the significant biomass of photosynthetically active plants (mainly dense moss carpets) and their resident organisms. The greater diversity detected in exposed soils may influence future changes in CO₂ flux in the studied region, for which comparisons of non-vegetated and vegetated soils with different microbial diversities are needed. This reinforces the necessity for studies to monitor the impact of resident biota on CO₂ flux in different areas of Maritime Antarctica, a region strongly impacted by climatic changes. Full article

The genus Pogonatum stands out as the most diverse within the family Polytrichaceae, encompassing over 50 species. Pogonatum tahitense has been recorded across various Pacific regions, including Hawaii in the United States and Tahiti in French Polynesia, as well as in Asia, such as in Taiwan in China, Java in Indonesia, and Sabah in Malaysia. In the current study, a specimen collected in Tibet, China, is described, confirming its taxonomic classification as P. tahitense through a comprehensive analysis integrating morphological evidence and molecular study based on sequences from the plastid (rbcL, rps4, trnL-F), mitochondrial (nad5), and nuclear (ITS2) regions. This documentation represents the first record of the species within mainland China. A time-calibrated, molecular-based phylogenetic analysis was conducted, employing various approaches for ancestral range inference. The findings suggest that P. tahitense originated during the Pleistocene epoch, approximately 1.8 mya, in Tibet, China. Full article

Mosses from the genus Polytrichum have been shown to contain rare benzonaphthoxanthenones compounds, and many of these have been reported to have important biological activities. In this study, extracts from Polytrichum formosum were analyzed in vitro for their inhibitory properties on collagenase and tyrosinase activity, two important cosmetic target enzymes involved respectively in skin aging and pigmentation. The 70% ethanol extract showed a dose-dependent inhibitory effect against collagenase (IC₅₀ = 4.65 mg/mL). The methanol extract showed a mild inhibitory effect of 44% against tyrosinase at 5.33 mg/mL. Both extracts were investigated to find the constituents having a specific affinity to the enzyme targets collagenase and tyrosinase. The known compounds ohioensin A (1), ohioensin C (3), and communin B (4), together with nor-ohioensin D (2), a new benzonaphthoxanthenone, were isolated from P. formosum. Their structures were determined by mass spectrometry and NMR spectroscopy. Compounds 1 (IC₅₀ = 71.99 µM) and 2 (IC₅₀ = 167.33 µM) showed inhibitory activity against collagenase. Compound 1 also exhibited inhibition of 30% against tyrosinase activity at 200 µM. The binding mode of the active compounds was theoretically generated by an in-silico approach against the 3D structures of collagenase and tyrosinase. These current results present the potential application from the moss P. formosum as a new natural source of collagenase and tyrosinase inhibitors. Full article

In this study, the organelle genomes of Polytrichum juniperinum Hedw. and Polytrichum strictum Menzies ex Brid. (Polytrichaceae, Bryophyta) from Antarctica were sequenced and compared with the plastomes of the model moss species Physcomitrella patens Brid. The sizes of the cpDNA in P. juniperinum and P. strictum were estimated to be 55,168 and 20,183 bp, respectively; the sizes of the mtDNA were 88,021 and 58,896 bp, respectively. The genomes are very similar to each other, with the possible loss of petN in the cpDNA, which also showed some gene inversions when compared with the cpDNAs of P. patens Brid. In the mtDNA, it is possible that rps10 was lost. In contrast, Antarctic Polytrichaceae species have nad7 and orf187, without the occurrence of rearrangement events. Phylogenomic analyses of the plastid and mitochondria revealed that the majority-rule tree suggests some differences in the plastids ancestry, however, P. juniperinum and P. strictum were grouped in the same clade in chloroplast, but in mitochondria P. strictum was grouped with Atrichum angustatum (Brid.) Bruch & Schimp. This study helped us understand the evolution of plastomes and chondriosomes in the family Polytrichaceae, and suggest a hybridization event with relation to the mitochondrial data. Full article