Anders Priemé

Peary Land, northern-most Greenland, is a cold desert region whose soil microbiome remains underexplored. This is the first study to explore the halotolerant soil microbiome of this region with culture-dependent methods. Forty-nine taxonomically diverse bacterial isolates were obtained from dry soil biocrust, surface soil and permafrost soil. Nine isolates were selected for whole genome sequencing; these genomes showed adaptations to their cold, saline native environment, such as cold shock proteins and a large number of osmoprotectant transporters. The genomes also contained several biosynthetic gene clusters, including a large variety of clusters putatively involved in the production of antimicrobial compounds. Furthermore, most of the sequenced genomes showed low digital DNA-DNA hybridisation to their closest relatives, suggesting that they represent novel species. Overall, this study demonstrates the unexplored potential of High Arctic deserts as a source of novel halotolerant bacteria and their secondary metabolites.

How climate change impacts pathogens in the natural environment is a critical ecological question. Yet, little is known of how rapid ongoing climate change in Antarctica and Patagonia will influence the fungal pathogens in the barren soils typical of these regions. Here, using DNA metabarcoding and LASSO regression, we identify climatic factors—and notably mean annual air temperature—as the best predictors for the taxonomic richness and relative abundance of fungal pathogens of plants and animals in barren soils sampled from along a 1900‐km transect through sub‐ and Maritime Antarctica and Patagonia. Projected changes to climate under three shared socioeconomic pathway scenarios (SSP1‐2.6, SSP3‐7.0, and SSP5‐8.5) were used to predict how soilborne pathogenic fungal communities will alter by 2071–2100. The SSP3‐7.0 and SSP5‐8.5 scenarios were projected to cause approximate doublings to the richness and abundance of phytopathogenic fungi in southern Maritime Antarctic soils. Weaker effects of these two scenarios were found on phytopathogens elsewhere on the transect and on animal pathogenic fungi. Changes to climate under the SSP1‐2.6 scenario had negligible impacts on both guilds. Edaphic factors explained lower amounts of variance in soil pathogenic fungal diversity and relative abundance than climatic factors. Our findings indicate higher frequencies of fungi causing grey molds, stem necroses, blights, scabs and leaf spots in warmer soils. They foreshadow end‐of‐century increases in the richness and abundance of phytopathogenic fungi inhabiting the barren soils of southern Maritime Antarctica, posing a threat to the region's flora as it colonizes these soils.

Inhalation of fungi in an indoor environment is a known respiratory irritant. Xerophilic/xerotolerant (following called xerophilic) fungal growth in heritage sites is a documented phenomenon. The potential health impact of spores of xerophilic fungi remains unclear. The aim of this study is to obtain knowledge about the potential of xerophilic Aspergillus species to induce production of reactive oxygen species (ROS) in a human cell line. Museum-derived isolates of A. pseudogracilis, 17 different xerophilic Aspergillus species from a fungal collection, and A. fumigatus (positive reference) were grown in pure culture and put into a standardized, single spore suspension. Granulocyte-like cells (HL-60) were exposed to these spore suspensions, and ROS production was monitored for 3 hours. Cytotoxicity and inflammatory cytokine expression were also determined after exposure to selected fungal species. For the 107 spores mL-1 exposure concentration, the museum isolates and 16 of 17 species induced a significant ROS production with different responses between species. Aspergillus domesticus induced the highest response, which was 3.5x higher than that of A. fumigatus. Of eight tested xerophilic species, all caused increased expression of the cytokines TNFα, CXCL8, IL-1β, and CCL2. Exposure to seven of the eight species decreased HL-60 cell viability significantly. Overall, this systematic comparison of xerophilic species suggests that they have the potential to initiate an inflammatory response in human leukocytes, and this potential varies between species and is dose-dependent. This study further demonstrates the importance of species identification for accurate occupational risk assessment.

Arctic soils store large amounts of organic matter (OM) and its decomposition by microorganisms and subsequent release of greenhouse gases (GHG) are sensitive to both temperature and moisture. Here, we use a temperature and moisture gradient across Greenland to decipher microbial emissions of CO2, N2O and CH4 as well as OM (cellulose, green tea and rooibos tea) decomposition under climate change. GHG fluxes and OM decomposition rates were linked to climatic and edaphic parameters, microbial functional genes, extracellular enzyme activities as well as prokaryotic ecological strategies based on a range of phenotypic and genomic traits. A prokaryotic ecological trait cluster with large genomes and long cells, the ability to form spores and high potential growth rates was associated with high in situ CO2 emissions, but not OM decomposition rates, presumably because activity alternated with inactivity due to spore formation. The large genomes suggest metabolic versatility such as the ability to degrade complex OM and may therefore mediate a positive effect of phenol oxidase activities on CO2 emissions. OM decomposition was promoted by a cluster with stress response traits such as high salinity tolerance, which may allow continuous activity throughout harsh conditions thereby sustaining continuous OM decomposition. Conversely, a cluster with small genomes and no stress response traits was associated with low CO2 emissions and litter decomposition rates which may be attributed to an efficient metabolism with low resource demand as well as periods of dormancy. Phenol oxidase activities were moreover key predictors of N2O emissions, indicating degradation of lignocellulosic OM to access N-rich compounds as a driver of N-cycling activities in N-limited Arctic soils. Collectively, our study unravels linkages between climate, microbial activities, prokaryotic traits and C- and N-cycling in Arctic soils highlighting that microbial ecological strategies can modulate OM decomposition.

Associations between feather mosses and cyanobacteria are crucial sources of new biologically available nitrogen (N) in arctic and subarctic ecosystems. The physiology of both mosses and cyanobacteria is strongly influenced by environmental factors such as temperature and moisture, which directly affect N ₂ fixation rates. These associations may be threatened by climate change, since it leads to warmer and drier conditions in polar regions. In this study, we investigated the N ₂ ‐fixing microbial communities associated with two common feather mosses across a precipitation gradient in the subarctic tundra, followed by a temperature and moisture experiment. Using acetylene reduction assays, nifH gene sequencing and qPCR, we evaluated how shifts in temperature and moisture influence nitrogenase activity and N ₂ ‐fixing community structure. Our results showed that N ₂ fixation was highest in sites with greater precipitation and increased with both temperature and moisture. Cyanobacteria dominated N ₂ ‐fixing communities, but currently unclassified bacteria also seemed to play a significant role, particularly at higher temperatures. The number of cyanobacterial nifH copies tended to remain stable or decrease with temperature, while the relative abundance of unclassified bacteria increased. These findings suggest that the N ₂ ‐fixing activity, abundance, and diversity of cyanobacteria associated with feather mosses in the subarctic will decline under warmer and drier conditions, potentially leading to a shift in the composition of feather moss‐associated microbial communities in a warmer Arctic, with potential consequences for N input into the ecosystem.

Strains CF4.4 ^T and KK5.5 ^T , previously isolated from samples of biocrust and permafrost, respectively, collected from Northern Greenland, were characterized using a polyphasic approach. Both strains were Gram-stain-positive, non-motile and non-endospore-forming cocci, and showed growth between 4 and 25 °C and 0–20% (w/v) NaCl. Strain CF4.4 ^T showed growth at pH 6–11 [optimal growth at pH 9–10 and 5% (w/v) NaCl]. Its 16S rRNA gene sequence showed similarities over 99% with Nesterenkonia jeogali JG-241 ^T , Nesterenkonia lutea YIM 70081 ^T and Nesterenkonia sandarakina YIM 70009 ^T . Based on digital DNA–DNA hybridization, the closest type strain to strain CF4.4 ^T was Nesterenkonia aurantiaca DSM 27373 ^T (31.8% similarity). The major respiratory menaquinones of strain CF4.4 ^T were MK-7, MK-8, MK-9 and MK-10, and its major cellular fatty acids were anteiso-C _15:0 , anteiso-C _17:0 and iso-C _16:0 . Its cells contained diphosphatidylglycerol, phosphatidylglycerol, an unidentified glycolipid and an unidentified phospholipid. Strain KK5.5 ^T showed growth at pH 6–10, with optimal growth at pH 8–9 and 0–2.5% (w/v) NaCl. Phylogenetic analysis based on its 16S rRNA gene sequence showed that it was most closely related to Arthrobacter halodurans JSM 078085 ^T (99.1%), Arthrobacter ginkgonis SYP-A7299 ^T (97.7%) and Zafaria cholistanensis NCCP-1664 ^T (97.6%). The genome of strain KK5.5 ^T showed the most similarity to A. halodurans DSM 21081 ^T (22.6%) based on digital DNA–DNA hybridization. The major respiratory menaquinones of strain KK5.5 ^T were MK-9(H ₂ ) and MK-10(H ₂ ), with small amounts of MK-11(H ₂ ). Its major cellular fatty acids were anteiso-C _15:0 , anteiso-C _17:0 and iso-C _15:0 , and its cells contained diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and an unidentified phospholipid. Based on the results presented in this study, we conclude that both strains represent novel species, for which we propose the names Nesterenkonia maliinae sp. nov. (type strain CF4.4 ^T =DSM 120326 ^T =LMG 34127 ^T ) and Arthrobacter arnarulunnguaqae sp. nov. (type strain KK5.5 ^T =DSM 120323 ^T =LMG 34129 ^T ).

Developments in the environmental DNA (eDNA) field have revolutionised our ability to map biodiversity by providing cost‐effective and non‐invasive means to survey organisms across the tree of life. In the terrestrial realm, a variety of eDNA sources have been employed, but we lack easily accessible and cosmopolitan sources of terrestrial eDNA. Here we document the value of a novel eDNA source for mapping lifeforms across the tree of life in temperate and tropical ecosystems: mosses (Bryophytes). First, we analysed eDNA from 25 moss patches collected using three sampling methods (swabbing, moss stubs, and washes of moss stubs) across three sites in Denmark. We detected 26 vertebrate species, 54 invertebrate genera, 21 vascular plant genera, and 553 bacterial and 210 fungal genera. Swabbing was sufficient to obtain eDNA, eliminating the need for destructive sampling of mosses. Subsequently, employing the swabbing approach in gallery forest and savanna ecosystems in Côte d'Ivoire we assessed its use for vertebrate detections. Metabarcoding of 29 moss swabs yielded 18 bird, 13 mammal, and two amphibian genera, confirming its applicability in the tropics. Our findings expand the current biodiversity monitoring toolkit by capitalising on a cosmopolitan and readily available terrestrial eDNA source.

The High Arctic deserts of remote northern Greenland are expected to become warmer and wetter due to climate change. Precipitation changes will increase fluctuations in surface soil salinity, and the same happens for thawed permafrost soil where stable salt concentrations are replaced with fluctuating salinity during annual freeze-thaw cycles. Both have unknown effects on the microbial communities and their emissions of microbial volatile organic compounds (MVOCs). These compounds are produced from various pathways mainly as secondary metabolites and have ecological and climatic implications when released into the environment and the atmosphere. Thus, it is important to explore the effects of environmental changes, such as changes in salinity, on soil microbial communities and their MVOC emissions. Here, we characterize the MVOC production of three novel bacterial isolates from northern Greenland throughout their growth period under low, moderate, and high salt concentrations. We demonstrate that salinity significantly alters both the quantity and composition of MVOCs emitted by all three strains, including changes in the emissions of sulphur- and nitrogen-containing compounds, potentially leading to ecosystem nutrient loss. The observed changes in MVOC profiles suggest that changes in soil salinity due to climate change could alter microbial metabolism and MVOC emissions, with potential implications for Arctic nutrient cycling and atmospheric chemistry.