Biology subjects

Prieme, A.

Publications and source records attributed to Prieme, A..

6 recordsLinked to original sources

bioRxiv2026

Exploring Volatile Sulfur Production by Arctic Soil Bacteria and Emissions from Thawing Permafrost

Warming of the Arctic enhances microbial activity and the decomposition of large stocks of organic matter retained in permafrost soil. Resulting changes in the availability of sulfur may lead to increased emissions of volatile sulfur compounds (VSCs), which impact atmospheric particle and cloud formation, terrestrial and aquatic acidification, and malodor. Marine microbial production of dimethyl sulfide (DMS) has been studied for decades but other VSCs have been largely ignored, while VSC emissions from terrestrial ecosystems are even less studied. Currently, we lack fundamental understanding of the metabolic processes behind VSC production in permafrost soil bacteria, essential for estimating how emissions may change due to thawing. To fill this knowledge gap, we measured VSC emissions from thawing permafrost and three bacterial strains isolated from Greenlandic permafrost and biological soil crust. We show that the bacterial strains produced high levels of VSCs in vitro - including hydrogen sulfide, methanethiol, DMS, dimethyl disulfide, and dimethyl trisulfide. We further show that the same VSCs were also emitted from permafrost upon thaw. Metabolic pathway mapping of the bacterial strains revealed both inorganic sulfate reduction pathways and amino acid metabolism behind bacterial VSC production. High production of VSCs in the late-active and stationary phase suggests connection to secondary metabolism, except for DMS which was linked to early growth, and possibly, primary energy metabolism. Our findings suggest that thawing increases VSC emissions from permafrost soil, possibly leading to higher input of sulfur into the atmosphere from the warming Arctic in the future.

microbiology↗

bioRxiv2025

Aridity drives global convergence of desert microbiomes and biogeochemical activities

Deserts cover a third of the worlds surface, supporting unique biomes and ecosystem services. Yet, we lack a comprehensive assessment of what defines and drives the microbial communities that dominate life in these regions. Here, we conducted a standardized field survey in contrasting cold, hot, and polar deserts across the seven continents, and observed geographically distant deserts share similar structure, function, and activities. Desert communities are dominated by genomically streamlined Actinobacteriota and Chloroflexota, and compared with non-desert soils, are significantly enriched with stress tolerance genes, mobile genetic elements, and antiviral strategies, revealing previously unknown ecological and evolutionary dynamics. Metabolically, these communities exhibit reduced capacity for carbohydrate and protein degradation, and instead are enriched for chemosynthetic carbon fixation, continuous energy harvesting using atmospheric trace gases and sunlight, and energy reserve biosynthesis. All sampled soils mediated respiration, trace gas oxidation, and carbon fixation, with detectable activity even in hyper-arid Atacama and Antarctic soils at the margins of life. Driver analyses identified aridity as the primary overriding driver of the microbial communities and biogeochemical activities. Collectively, these findings suggest that aridity selects for metabolically self-sufficient taxa capable of continuously meeting energy and carbon needs independently of vegetation-derived inputs, while enduring physicochemical stressors and potentially elevated viral pressure. These new insights are integral to forecast the future of soils amid increasing desertification. Significance statementDesert soils occupy a vast and expanding portion of Earth, yet what defines and governs their dominant microbial life remains incompletely defined. By assessing the composition, capabilities, and activities of microbial communities across deserts on all seven continents, we identify unifying signatures of life under extreme water limitation. We show microbial communities are highly self-sufficient, capable of acquiring energy and carbon even where plant inputs are minimal. This planetary-scale understanding of the desert microbiome has important ramifications for forecasting potential shifts of microbial communities and the services they provide as desertification intensifies.

microbiology↗

bioRxiv2025

Volatilomic complexity of three Northern Greenland bacterial isolates across a salt gradient

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.

microbiology↗

bioRxiv2025

Genomic adaptations of novel halotolerant bacteria from extreme North Greenland

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 biological soil crust, 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 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.

microbiology↗

bioRxiv2025

Climate change impacts the structure and nitrogen-fixing activities of subarctic feather moss microbiomes across a precipitation gradient

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 N2 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 N2-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 N2-fixing community structure. Our results showed that N2 fixation was highest in sites with greater precipitation and increased with both temperature and moisture. Cyanobacteria dominated N2-fixing communities, but currently unclassified bacteria also seemed to play a significant role, particularly at high temperatures. The number of cyanobacterial nifH copies tended to decrease with temperature, while the relative abundance of unclassified bacteria increased. These findings suggest that the N2-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.

ecology↗

bioRxiv2019

Transcriptomic responses to warming and cooling of an Arctic tundra soil microbiome

BackgroundArctic surface soils experience pronounced seasonal changes in temperature and chemistry. However, it is unclear how these changes affect microbial degradation of organic matter, nitrogen cycling and microbial stress responses. We combined measurements of microbiome transcriptional activity, CO2 production, and pools of carbon and nitrogen to investigate the microbial response to warming in the laboratory, from -10 {degrees}C to 2 {degrees}C, and subsequent cooling, from 2 {degrees}C to -10 {degrees}C, of a high Arctic tundra soil from Svalbard, Norway.\n\nResultsGene expression was unaffected by warming from -10 {degrees}C to -2 {degrees}C and by cooling from -2 {degrees}C to -10 {degrees}C, while upon freezing (2 {degrees}C to -2 {degrees}C) a defense response against oxidative stress was observed. Following modest transcriptional changes one day after soil thaw, a more pronounced response was observed after 17 days, involving numerous functions dominated by an upregulation of genes involved in transcription, translation and chaperone activity. Transcripts related to carbohydrate metabolism and degradation of complex polymers (e.g. cellulose, hemicellulose and chitin) were also enhanced following 17 days of soil thaw, which was accompanied by a four-fold increase in CO2 production. In addition, anaerobic ammonium oxidation and turnover of organic nitrogen were upregulated. In contrast, nitrification, denitrification and assimilatory nitrate reduction were downregulated leading to an increase in the concentration of soil inorganic nitrogen.\n\nConclusionthe microorganisms showed negligible response to changes in sub-zero temperatures and a delayed response to thaw, which after 17 days led to upregulation of soil organic matter degradation and enhanced CO2 production, as well as downregulation of key pathways in nitrogen cycling and a concomitant accumulation of inorganic nitrogen available for plants.

microbiology↗