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Polar environments pose extreme challenges for life due to low temperatures, limited water, high radiation, and frozen landscapes. Despite these harsh conditions, numerous macro and microorganisms have developed adaptive strategies to reduce the detrimental effects of extreme cold. A primary survival tactic involves avoiding or tolerating intra and extracellular freezing. Many organisms achieve this by maintaining a supercooled state by producing small organic compounds like sugars, glycerol, and amino acids, or through increasing solute concentration. Another approach is the synthesis of ice-binding proteins, specifically antifreeze proteins (AFPs), which hinder ice crystal growth below the melting point. This adaptation is crucial for preventing intracellular ice formation, which could be lethal, and ensuring the presence of liquid water around cells. AFPs have independently evolved in different species, exhibiting distinct thermal hysteresis and ice structuring properties. Beyond their ecological role, AFPs have garnered significant attention in biotechnology for potential applications in the food, agriculture, and pharmaceutical industries. This review aims to offer a thorough insight into the activity and impacts of AFPs on water, examining their significance in cold-adapted organisms, and exploring the diversity of microbial AFPs. Using a meta-analysis from cultivation-based and cultivation-independent data, we evaluate the correlation between AFP-producing microorganisms and cold environments. We also explore small and large-scale biotechnological applications of AFPs, providing a perspective for future research. [ABSTRACT FROM AUTHOR]

The Barents Sea shelf is one of the most economically promising regions in the Arctic in terms of its resources and geographic location. However, benthic microbial communities of the northeastern Barents Sea are still barely studied. Here, we present a detailed systematic description of the structures of microbial communities located in the sediments and bottom water of the northeastern Barents Sea based on 16S rRNA profiling and a qPCR assessment of the total prokaryotic abundance in 177 samples. Beta- and alpha-diversity analyses revealed a clear difference between the microbial communities of diverse sediment layers and bottom-water fractions. We identified 101 microbial taxa whose representatives had statistically reliable distribution patterns between these ecotopes. Analysis of the correlation between microbial community structure and geological data yielded a number of important results—correlations were found between the abundance of individual microbial taxa and bottom relief, thickness of marine sediments, presence of hydrotrolite interlayers, and the values of pH and Eh. We also demonstrated that a relatively high abundance of prokaryotes in sediments can be caused by the proliferation of Deltaproteobacteria representatives, in particular, sulfate and iron reducers. [ABSTRACT FROM AUTHOR]

Thermokarst lakes are important conduits for organic carbon sequestration, soil organic matter (soil-OM) decomposition and release of atmospheric greenhouse gases in the Arctic. They can be classified as either floating-ice lakes, which sustain a zone of unfrozen sediment (talik) at the lakebed year-round, or as bedfast-ice lakes, which freeze all the way to the lakebed in winter. Another key characteristic of thermokarst lakes are their eroding shorelines, depending on the surrounding landscape, they can play a major role in supplying the lakebeds with sediment and OM. These differences in winter ice regime and eroding shorelines are key factors which determine the quantity and quality of OM in thermokarst lake sediments. We used an array of physical, geochemical, and microbiological tools to identify the differences in the environmental conditions, sedimentary characteristics, carbon stocks and microbial community compositions in the sediments of a bedfast-ice and a floating-ice lake in Far East Siberia with different eroding shorelines. Our data show strong differences across most of the measured parameters between the two lakes. For example, the floating-ice lake contains considerably lower amounts of sediment organic matter and dissolved organic carbon, both of which also appear to be more degraded in comparison to the bedfast-ice lake, based on their stable carbon isotope composition (δ13C). We also document clear differences in the microbial community composition, for both archaea and bacteria. We identified the lake water depth (bedfast-ice vs. floating-ice) and shoreline erosion to be the two most likely main drivers of the sedimentary, microbial and biogeochemical diversity in thermokarst lakes. With ongoing climate warming, it is likely that an increasing number of lakes will shift from a bedfast- to a floating-ice state, and that increasing levels of shoreline erosion will supply the lakes with sediments. Yet, still little is known about the physical, biogeochemical and microbial differences in the sediments of these lake types and how different eroding shorelines impact these lake systems. [ABSTRACT FROM AUTHOR]

Within the Svalbard archipelago, Kongsfjorden is an important marine ecosystem that is recognised as one of the main representative Arctic glacial fjords. Prokaryotic organisms are key drivers of important ecological processes such as carbon fluxes, nutrient mineralisation, and energy transfer, as well as sentinels of environmental pollution, especially in sediments, that are a repository of contaminants. In some areas of the Arctic, the structure and metabolic activity of the microbial community in the organic matter turnover and globally in the functioning of the benthic domain are mostly still unknown. A snapshot of the main microbial parameters such as bacterial abundance (by microscopic and plate counts), structure (by 16S rRNA sequencing), and metabolic activity was provided in Ny-Ålesund harbour, contextually in seawater and sediment samples. Fluorogenic substrates were used to assess the microbial ability to utilise organic substrates such as proteins, polysaccharides, and organic phosphates through specific enzymatic assays (leucine aminopeptidase—LAP, beta-glucosidase—ß-GLU, and alkaline phosphatase—AP, respectively). The metabolic profiles of psychrophilic heterotrophic bacterial isolates were also screened using a qualitative assay. The phylogenetic analysis of the microbial community revealed that Proteobacteria prevailed among the observed taxonomic groups. Several of the observed sequences were assigned to clones found in harbours, microbial biofilms, antifouling paints, or oil-polluted facilities of cold environments, highlighting a signature of human pressure on the polar habitat of Ny-Ålesund harbour. [ABSTRACT FROM AUTHOR]

Most lakes in the world are permanently or seasonally covered with ice. However, little is known about the distribution of microbes and their influencing factors in ice-covered lakes worldwide. Here we analyzed the microbial community composition in the waters of 14 ice-covered lakes in the Hoh Xil region of northern Qing-Tibetan Plateau (QTP), and conducted a meta-analysis by integrating published microbial community data of ice-covered lakes in the tripolar regions (the Arctic, Antarctica and QTP). The results showed that there were significant differences in microbial diversity, community composition and distribution patterns in the ice-covered tripolar lakes. Microbial diversity and richness were lower in the ice-covered QTP lakes (including the studied lakes in the Hoh Xil region) than those in the Arctic and Antarctica. In the ice-covered lakes of Hoh Xil, prokaryotes are mainly involved in S-metabolic processes, making them more adaptable to extreme environmental conditions. In contrast, prokaryotes in the ice-covered lakes of the Arctic and Antarctica were predominantly involved in carbon/nitrogen metabolic processes. Deterministic (salinity and nutrients) and stochastic processes (dispersal limitation, homogenizing dispersal and drift) jointly determine the geographical distribution patterns of microorganisms in ice-covered lakes, with stochastic processes dominating. These results expand the understanding of microbial diversity, distribution patterns, and metabolic processes in polar ice-covered lakes. • Microbial distribution patterns differed significantly in the tripolar ice-covered lakes. • Microbial diversity and metabolism were greatly limited by nutrients in ice-covered lakes. • Salinity and nutrients were deterministic factors that shaped microbial assembly. • Stochastic processes predominated over deterministic processes in shaping the biogeographic distribution. [ABSTRACT FROM AUTHOR]

Cryoconite holes, supraglacial depressions containing water and microbe-mineral aggregates, are known to be hotspots of microbial diversity on glacial surfaces. Cryoconite holes form in a variety of locations and conditions, which impacts both their structure and the community that inhabits them. Using high-throughput 16S and 18S rRNA gene sequencing, we have investigated the communities of a wide range of cryoconite holes from 15 locations across the Arctic and Antarctic. Around 24 bacterial and 11 eukaryotic first-rank phyla were observed in total. The various biotic niches (grazer, predator, photoautotroph, and chemotroph), are filled in every location. Significantly, there is a clear divide between the bacterial and microalgal communities of the Arctic and that of the Antarctic. We were able to determine the groups contributing to this difference and the family and genus level. Both polar regions contain a "core group" of bacteria that are present in the majority of cryoconite holes and each contribute >1% of total amplicon sequence variant (ASV) abundance. Whilst both groups contain Microbacteriaceae, the remaining members are specific to the core group of each polar region. Additionally, the microalgal communities of Arctic cryoconite holes are dominated by Chlamydomonas whereas the Antarctic cryoconite holes are dominated by Pleurastrum. Therefore cryoconite holes may be a global feature of glacier landscapes, but they are inhabited by regionally distinct microbial communities. Our results are consistent with the notion that cryoconite microbiomes are adapted to differing conditions within the cryosphere. [ABSTRACT FROM AUTHOR]

Understanding microbial niche variability in polar regions can provide insights into the adaptive diversification of microbial lineages in extreme environments. Compositions of microbial communities in Arctic soils are well documented but a comprehensive multidomain diversity assessment of rocks remains insufficiently studied. In this study, we obtained two types of rocks (sandstone and limestone) and soils around the rocks in a high Arctic polar desert (Svalbard), and examined the compositions of archaeal, bacterial, fungal, and protistan communities in the rocks and soils. The microbial community structure differed significantly between rocks and soils across all microbial groups at higher taxonomic levels, indicating that Acidobacteria, Gemmatimonadetes, Latescibacteria, Rokubacteria, Leotiomycetes, Pezizomycetes, Mortierellomycetes, Sarcomonadea, and Spirotrichea were more abundant in soils, whereas Cyanobacteria, Deinococcus-Thermus, FBP, Lecanoromycetes, Eurotiomycetes, Trebouxiophyceae, and Ulvophyceae were more abundant in rocks. Interestingly, fungal communities differed markedly between two different rock types, which is likely to be ascribed to the predominance of distinct lichen-forming fungal taxa (Verrucariales in limestone, and Lecanorales in sandstone). This suggests that the physical or chemical properties of rocks could be a major determinant in the successful establishment of lichens in lithic environments. Furthermore, the biotic interactions among microorganisms based on co-occurrence network analysis revealed that Polyblastia and Verrucaria in limestone, and Atla , Porpidia , and Candelariella in sandstone play an important role as keystone taxa in the lithic communities. Our study shows that even in niches with the same climate regime and proximity to each other, heterogeneity of edaphic and lithic niches can affect microbial community assembly, which could be helpful in comprehensively understanding the effects of niche on microbial assembly in Arctic terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

We assessed the microbial community structure of six arctic lakes in West Greenland and investigated relationships to lake physical and chemical characteristics. Lakes from the ice sheet region exhibited the highest species richness, while inland and plateau lakes had lower observed taxonomical diversity. Lake habitat differentiation during summer stratification appeared to alter within lake microbial community composition in only a subset of lakes, while lake variability across regions was a consistent driver of microbial community composition in these arctic lakes. Principal coordinate analysis revealed differentiation of communities along two axes: each reflecting differences in morphometric (lake surface area), geographic (latitude and distance from the ice sheet), physical lake variables (water clarity), and lakewater chemistry (dissolved organic carbon [DOC], dissolved oxygen [DO], total nitrogen [TN], and conductivity). Understanding these relationships between environmental variables and microbial communities is especially important as heterotrophic microorganisms are key to organic matter decomposition, nutrient cycling, and carbon flow through nutrient poor aquatic environments in the Arctic. [ABSTRACT FROM AUTHOR]

The Arctic ecosystem, a reservoir of genetic microbial diversity, represents a virtually unlimited source of microorganisms that could interact with human beings. Despite continuous exploration of Arctic habitats and description of their microbial communities, bacterial phenotypes commonly associated with pathogenicity, such as hemolytic activity, have rarely been reported. In this study, samples of snow, fresh and marine water, soil, and sediment from several habitats in the Arctic archipelago of Svalbard were collected during Summer, 2017. Bacterial isolates were obtained after incubation on oligotrophic media at different temperatures and their hemolytic potential was assessed on sheep blood agar plates. Partial (α) or true (β) hemolysis was observed in 32 out of 78 bacterial species. Genes expressing cytolytic compounds, such as hemolysins, likely increase the general fitness of the producing microorganisms and confer a competitive advantage over the availability of nutrients in natural habitats. In environmental species, the nutrient-acquisition function of these compounds presumably precedes their function as toxins for mammalian erythrocytes. However, in the light of global warming, the presence of hemolytic bacteria in Arctic environments highlights the possible risks associated with these microorganisms in the event of habitat melting/destruction, ecosystem transition, and re-colonization. [ABSTRACT FROM AUTHOR]

Oil spilled in marine environments can settle to the seafloor through aggregation and sedimentation processes. This has been predicted to be especially relevant in the Arctic due to plankton blooms initiated by melting sea ice. These conditions exist in the Kivalliq region in Nunavut, Canada, where elevated shipping traffic has increased the risk of accidental spills. Experimental microcosms combining surface sediment and crude oil were incubated at 4 °C over 21 weeks to evaluate the biodegradation potential of seabed microbiomes. Sediments sampled near the communities of Arviat and Chesterfield Inlet were assessed for biodegradation capabilities by combining hydrocarbon geochemistry with 16S rRNA gene and metagenomic sequencing, revealing decreased microbial diversity but enrichment of oil-degrading taxa. Alkane and aromatic hydrocarbon losses corresponded to detection of genes and genomes that encode enzymes for aerobic biodegradation of these compounds, pointing to the utility of marine microbiome surveys for predicting the fate of oil released into Arctic marine environments. [Display omitted] • Marine oil spill risks are linked to shipping in Kivalliq, Nunavut. • Permanently cold sediment microbiomes degrade alkane and aromatic hydrocarbons. • Biodegradation genes point to natural attenuation potential in the baseline microbiome. • Crude oil exposure enriches some taxa but causes decrease in microbial diversity. [ABSTRACT FROM AUTHOR]

Global warming induced sea ice loss increases Arctic maritime traffic, enhancing the risk of ecosystem contamination from fuel spills and nutrient loading. The impact of marine diesel on bacterial metabolic activity and diversity, assessed by colorimetric assay, 16S rRNA and metagenomic sequencing, of Northwest Passage (Arctic Ocean) beach sediments was assessed with nutrient amendment at environmentally relevant temperatures (5 and 15 °C). Higher temperature and nutrients stimulated microbial activity, while diesel reduced it, with metabolism inhibited at and above 0.01 % (without nutrients) and at 1 % (with nutrients) diesel inclusions. Diesel exposure significantly decreased microbial diversity and selected for Psychrobacter genus. Microbial hydrocarbon degradation, organic compound metabolism, and exopolysaccharide production gene abundances increased under higher diesel concentrations. Metagenomic binning recovered nine MAGs/bins with hydrocarbon degradation genes. We demonstrate a nutrients' rescue-type effect in diesel contaminated microbial communities via enrichment of microorganisms with stress response, aromatic compound, and ammonia assimilation metabolisms. [Display omitted] • Diesel exposure reduces microbial diversity in Arctic beach sediments • Selection for the Psychrobacter genus at higher diesel concentrations • Nutrients help maintain microbial activity when sediment is exposed to marine diesel • Diesel enriched for phenylalanine metabolism & malate synthesis microbial functions • Diesel selected for microorganisms with (an)aerobic hydrocarbon degradation potential [ABSTRACT FROM AUTHOR]

Microbial communities in the glacier forefield of Styggedalsbreen, Norway, were investigated along a chronosequence from newly exposed soil to vegetated soils using next-generation sequencing of the 16S rRNA gene. In order to monitor the short-term effect of temperature on community successions along the soil gradient, the soil samples were incubated at three different temperatures (5°C, 10°C and 22°C). The microbial community composition along the chronosequence differed according to distance from the glacial terminus and incubation temperature. Samples close to the glacier terminus were dominated by Proteobacteria at 5°C and 10°C, while at 22°Cmembers of Chloroflexi, Acidobacteria and Verrucomicrobia in addition to Proteobacteria accounted for most of the diversity, indicating that sites close to the glacier terminus are more closely related to former subglacial environments. Within the Archaea domain, members of the phylum Euryarchaeota dominated in samples closer to the glacier terminus with a shift to members of the phyla Thaumarchaeota-Crenarchaeota with increased soil age. Our data indicate that composition and diversity of the microbial communities along the glacier forefield depend not only on exposure time but are also to a large degree influenced by soil surface temperature and soil maturation. [ABSTRACT FROM AUTHOR]

The Arctic region is a unique environment, subject to extreme environmental conditions, shaping life therein and contributing to its sensitivity to environmental change. The Arctic is under increasing environmental pressure from anthropogenic activity and global warming. The unique microbial diversity of Arctic regions, that has a critical role in biogeochemical cycling and in the production of greenhouse gases, will be directly affected by and affect, global changes. This article reviews current knowledge and understanding of microbial taxonomic and functional diversity in Arctic soils, the contributions of microbial diversity to ecosystem processes and their responses to environmental change. [ABSTRACT FROM AUTHOR]

Surface ice and cryoconite holes of two types of polythermal Svalbard Glaciers (Hans Glacier-grounded tidewater glacier and Werenskiold Glacier-land-based valley glacier) were investigated in terms of chemical composition, microbial abundance and diversity. Gathered data served to describe supraglacial habitats and to compare microbe-environment interactions on those different type glaciers. Hans Glacier samples displayed elevated nutrient levels (DOC, nitrogen and seston) compared to Werenskiold Glacier. Adjacent tundra formations, bird nesting sites and marine aerosol were candidates for allochtonic enrichment sources. Microbial numbers were comparable on both glaciers, with surface ice containing cells in the range of 10 mL and cryoconite sediment 10 g dry weight. Denaturating gradient gel electrophoresis band-based clustering revealed differences between glaciers in terms of dominant bacterial taxa structure. Microbial community on Werenskiold Glacier benefited from the snow-released substances. On Hans Glacier, this effect was not as pronounced, affecting mainly the photoautotrophs. Over-fertilization of Hans Glacier surface was proposed as the major factor, desensitizing the microbial community to the snow melt event. Nitrogen emerged as a limiting factor in surface ice habitats, especially to Eukaryotic algae. [ABSTRACT FROM AUTHOR]

This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters ( Bacteroidetes and Firmicutes). [ABSTRACT FROM AUTHOR]

During the spring of 2009, as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population diversity, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the culturing and gene-sequence-based identification approach, we utilized a state-of-the-art genomic next-generation sequencing (NGS) technique to examine the diversity of bacterial communities in Arctic samples. Known phyla or candidate divisions were detected (11-18) with the majority of sequences (12.3-83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The number of genera detected ranged from, 101-245. The highest number of cultivable bacteria was observed in frost flowers (FFs) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU m L-1, respectively; and for cultivable fungi 5 ± 1 CFU m L-1 in windpack (WP) and blowing snow (BS). Morphology/elemental composition and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy with energy-dispersive X-ray spectroscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolates ranged from -20.3 ± 1.5 to -15.7 ± 5.6 °C, and for melted snow samples from -9.5 ± 1.0 to -18.4 ± 0.1 °C. An isolate belonging to the genus Bacillus (96% similarity) had ice nucleation activity of -6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed that a seemingly diverse community of bacteria exists in the Arctic with some taxa possibly originating from distinct ecological environments. We discuss the potential impact of snow microorganisms in the freezing and melting process of the snowpack in the Arctic. [ABSTRACT FROM AUTHOR]

Cryoconite holes are known as foci of microbial diversity and activity on polar glacier surfaces, but are virtually unexplored microbial habitats in alpine regions. In addition, whether cryoconite community structure reflects ecosystem functionality is poorly understood. Terminal restriction fragment length polymorphism and Fourier transform infrared metabolite fingerprinting of cryoconite from glaciers in Austria, Greenland and Svalbard demonstrated cryoconite bacterial communities are closely correlated with cognate metabolite fingerprints. The influence of bacterial-associated fatty acids and polysaccharides was inferred, underlining the importance of bacterial community structure in the properties of cryoconite. Thus, combined application of T-RFLP and FT- IR metabolite fingerprinting promises high throughput, and hence, rapid assessment of community structure-function relationships. Pyrosequencing revealed Proteobacteria were particularly abundant, with Cyanobacteria likely acting as ecosystem engineers in both alpine and Arctic cryoconite communities. However, despite these generalities, significant differences in bacterial community structures, compositions and metabolomes are found between alpine and Arctic cryoconite habitats, reflecting the impact of local and regional conditions on the challenges of thriving in glacial ecosystems. [ABSTRACT FROM AUTHOR]

The polar regions, comprising the Antarctic, Arctic and Tibetan Plateau, represent the most extreme environments on Earth. Soils across the polar regions harbor diverse microorganisms, which dominate the biogeochemical cycling. However, polar soil microbial diversity is largely underrepresented, and has not been directly compared with the non-polar regions at a global scale, which hinders our understanding of the potential importance of polar microbial diversity. In this study, we investigated the global microbial diversity and taxonomy by comparing 1114 soils, derived from the Antarctic (203), Arctic (432), Tibetan Plateau (104) and non-polar regions (375) across all continents. Soil microbial diversity was found to increase gradually from the Antarctic < Arctic < Tibetan Plateau and < non-polar regions. Soil microbial diversity dominantly corresponded to mean summer temperature in the polar regions and to soil pH in non-polar regions, respectively. Soil microbial community structure significantly differed across the different biogeographical regions, while the Antarctic exhibited the highest habitat-specificity. Over 26,000 phylotypes were observed across global soils, of which 21.8% were unique to the three poles, and 21.2% were apparently ubiquitous globally. Polar soils were dominated by fewer phylotypes, but individual phylotype showed greater dominance than that in non-polar regions. Our study reveals unique patterns of soil microbial diversity and taxonomic compositions in polar regions, and highlights the importance of environmental stresses in controlling soil microbial community. [Display omitted] • Polar soil microbial diversity (SMD) was compared with global non-polar regions. • 21% of the phylotypes were globally ubiquitous, 22% were three-poles specific. • Actinobacteria was the most ubiquitous, Firmicutes was predominately endemic. • SMD corresponded to summer temperature in poles and to soil pH in non-poles. • Polar soils were dominated by fewer microbial phylotypes with greater dominance. [ABSTRACT FROM AUTHOR]

The Arctic environment is undergoing changes due to climate shifts, receiving contaminants from distant sources and experiencing increased human activity. Climate change may alter microbial functioning by increasing growth rates and substrate use due to increased temperature. This may lead to changes of process rates and shifts in the structure of microbial communities. Biodiversity may increase as the Arctic warms and population shifts occur as psychrophilic/psychrotolerant species disappear in favor of more mesophylic ones. In order to predict how ecological processes will evolve as a function of global change, it is essential to identify which populations participate in each process, how they vary physiologically, and how the relative abundance, activity and community structure will change under altered environmental conditions. This review covers aspects of the importance and implication of snowpack in microbial ecology emphasizing the diversity and activity of these critical members of cold zone ecosystems. [ABSTRACT FROM AUTHOR]

Tundra ecosystem is of importance for its high accumulation of organic carbon and vulnerability to future climate change. Microorganisms play a key role in carbon dynamics of the tundra ecosystem by mineralizing organic carbon. We assessed both ecosystem process rates and community structure of Bacteria, Archaea, and Fungi in different soil layers (surface organic layer and subsurface mineral soil) in an Arctic soil ecosystem located at Spitsbergen, Svalbard during the summer of 2008 by using biochemical and molecular analyses, such as enzymatic assay, terminal restriction fragment length polymorphism (T-RFLP), quantitative polymerase chain reaction (qPCR), and pyrosequencing. Activity of hydrolytic enzymes showed difference according to soil type. For all three microbial communities, the average gene copy number did not significantly differ between soil types. However, archaeal diversities appeared to differ according to soil type, whereas bacterial and fungal diversity indices did not show any variation. Correlation analysis between biogeochemical and microbial parameters exhibited a discriminating pattern according to microbial or soil types. Analysis of the microbial community structure showed that bacterial and archaeal communities have different profiles with unique phylotypes in terms of soil types. Water content and hydrolytic enzymes were found to be related with the structure of bacterial and archaeal communities, whereas soil organic matter (SOM) and total organic carbon (TOC) were related with bacterial communities. The overall results of this study indicate that microbial enzyme activity were generally higher in the organic layer than in mineral soils and that bacterial and archaeal communities differed between the organic layer and mineral soils in the Arctic region. Compared to mineral soil, peat-covered organic layer may represent a hotspot for secondary productivity and nutrient cycling in this ecosystem. [ABSTRACT FROM AUTHOR]

The cryosphere presents some of the most challenging conditions for life on earth. Nevertheless, (micro)biota survive in a range of niches in glacial systems, including water-filled depressions on glacial surfaces termed cryoconite holes (centimetre to metre in diameter and up to 0.5 m deep) that contain dark granular material (cryoconite). In this study, the structure of bacterial and eukaryotic cryoconite communities from ten different locations in the Arctic and Antarctica was compared using T- RFLP analysis of rRNA genes. Community structure varied with geography, with greatest differences seen between communities from the Arctic and the Antarctic. DNA sequencing of rRNA genes revealed considerable diversity, with individual cryoconite hole communities containing between six and eight bacterial phyla and five and eight eukaryotic 'first-rank' taxa and including both bacterial and eukaryotic photoautotrophs. Bacterial Firmicutes and Deltaproteobacteria and Epsilonproteobacteria, eukaryotic Rhizaria, Haptophyta, Choanomonada and Centroheliozoa, and archaea were identified for the first time in cryoconite ecosystems. Archaea were only found within Antarctic locations, with the majority of sequences (77%) related to members of the Thaumarchaeota. In conclusion, this research has revealed that Antarctic and Arctic cryoconite holes harbour geographically distinct highly diverse communities and has identified hitherto unknown bacterial, eukaryotic and archaeal taxa, therein. [ABSTRACT FROM AUTHOR]

Abstract: Climate change is predicted to increase the frequency of freeze-thaw events in Arctic, sub-Arctic, Boreal, and some temperate regions. The aim of this study was to examine the effects of freeze-thaw events on abundance and composition of the soil community, thereby clarifying whether freeze-thaw events act as a distributing factor on microbes and nematodes. We investigated comparable soils from sites with and without seasonal freezing to determine whether the communities in these soils responded differently to freeze-thaw events and whether freeze tolerance of nematodes is adaptive. In a microcosm experiment we assessed microbe and nematode abundances and nematode community composition. Continuous freezing had a greater effect on both abundance and community composition of soil organisms than successive freeze-thaw cycles. In addition, freezing had clearer effects on the nematode community than on microbial biomass. The previous freezing history of the sampling sites played a role in the changes of the nematode community under freezing exposure. In the soil that had never been exposed to freezing, freezing particularly inhibited members of the nematode community that usually colonize patches of high microbial activity very rapidly and limited their ability to fill their niche as extreme colonizers. This may play a role for the ability of non-freezing adapted nematode communities to spread northwards with climate change. [Copyright &y& Elsevier]

Abstract: Technological advances allowing routine nanoparticle (NP) manufacture have enabled their use in electronic equipment, foods, clothing and medical devices. Although some NPs have antibacterial activity, little is known about their environmental impact and there is no information on the influence of NPs on soil in the possibly vulnerable ecosystems of polar regions. The potential toxicity of 0.066% silver, copper or silica NPs on a high latitude (>78°N) soil was determined using community level physiological profiles (CLPP), fatty acid methyl ester (FAME) assays and DNA analysis, including sequencing and denaturing gradient gel electrophoresis (DGGE). The results of these different investigations were amalgamated in order to develop a community toxicity indicator, which revealed that of the three NPs examined, silver NPs could be classified as highly toxic to these arctic consortia. Subsequent culture-based studies confirmed that one of the community-identified plant-associating bacteria, Bradyrhizobium canariense, appeared to have a marked sensitivity to silver NPs. Thus, NP contamination of arctic soils particularly by silver NPs is a concern and procedures for mitigation and remediation of such pollution should be a priority for investigation. [Copyright &y& Elsevier]

In arctic glacier moraines, bioweathering primed by microbial iron oxidizers creates fertility gradients that accelerate soil development and plant establishment. With the aim of investigating the change of bacterial diversity in a pyrite-weathered gradient, we analyzed the composition of the bacterial communities involved in the process by sequencing 16S rRNA gene libraries from different biological soil crusts (BSC). Bacterial communities in three BSC of different morphology, located within 1 m distance downstream a pyritic conglomerate rock, were significantly diverse. The glacier moraine surrounding the weathered site showed wide phylogenetic diversity and high evenness with 15 represented bacterial classes, dominated by Alphaproteobacteria and pioneer Cyanobacteria colonizers. The bioweathered area showed the lowest diversity indexes and only nine bacterial families, largely dominated by Acidobacteriaceae and Acetobacteraceae typical of acidic environments, in accordance with the low pH of the BSC. In the weathered BSC, iron-oxidizing bacteria were cultivated, with counts decreasing along with the increase of distance from the rock, and nutrient release from the rock was revealed by environmental scanning electron microscopy-energy dispersive X-ray analyses. The vegetated area showed the presence of Actinomycetales, Verrucomicrobiales, Gemmatimonadales, Burkholderiales, and Rhizobiales, denoting a bacterial community typical of developed soils and indicating that the lithoid substrate of the bare moraine was here subjected to an accelerated colonization, driven by iron-oxidizing activity. [ABSTRACT FROM AUTHOR]

Abstract: Seacoast to inland soil transects of 1 and 2km were researched over 2years to understand the microbial diversity in a post ice age, isostatically, rebounding, soil environment. Community level substrate utilization analysis and 16S rDNA eubacterial diversity were employed. The community level substrate analysis demonstrated that regardless of the location along the transect from seacoast to forest, sandy or peat soil, the microbial diversity (Shannon diversity index about 3) was virtually the same. Shannon diversity indexes based on PCR-DGGE analysis yielded values between about 0.6 and about 2 depending on the sand or peat soil type and the year the samples were collected and analyzed (2002 and 2003). Regardless of the genetic diversity, the soils exhibited similar metabolic capabilities. This is a good example of redundant, functional, physiology regardless of the species present at each location along the transects. [Copyright &y& Elsevier]

We studied the microbial diversity in the sediment from the Kongsfjorden, Svalbard, Arctic, in the summer of 2005 based on the analysis of 16S rRNA and 18S rRNA gene clone libraries. The sequences of the cloned 16S rRNA and 18S rRNA gene inserts were used to determine the species identity or closest relatives by comparison with sequences of known species. Compared to the other samples acquired in Arctic and Antarctic, which are different from that of ours, the microbial diversity in our sediment is much higher. The bacterial sequences were grouped into 11 major lineages of the domain Bacteria: Proteobacteria (include α-, β-, γ-, δ-, and ε-Proteobacteria); Bacteroidetes; Fusobacteria; Firmicutes; Chloroflexi; Chlamydiae; Acidobacteria; Actinobacteria; Planctomycetes; Verrucomicrobiae and Lentisphaerae. Crenarchaeota were dominant in the archaeal clones containing inserts. In addition, six groups from eukaryotes including Cercozoa, Fungi, Telonema, Stramenopiles, Alveolata, and Metazoa were identified. Remarkably, the novel group Lentisphaerae was reported in Arctic sediment at the first time. Our study suggested that Arctic sediment as a unique habitat may contain substantial microbial diversity and novel species will be discovered. [ABSTRACT FROM AUTHOR]

Bacteriophages are found wherever microbial life is present and play a significant role in aquatic ecosystems. They mediate microbial abundance, production, respiration, diversity, genetic transfer, nutrient cycling and particle size distribution. Most studies of bacteriophage ecology have been undertaken at temperate latitudes. Data on bacteriophages in polar inland waters are scant but the indications are that they play an active and dynamic role in these microbially dominated polar ecosystems. This review summarises what is presently known about polar inland bacteriophages, ranging from subglacial Antarctic lakes to glacial ecosystems in the Arctic. The review examines interactions between bacteriophages and their hosts and the abiotic and biotic variables that influence these interactions in polar inland waters. In addition, we consider the proportion of the bacteria in Arctic and Antarctic lake and glacial waters that are lysogenic and visibly infected with viruses. We assess the relevance of bacteriophages in the microbial loop in the extreme environments of Antarctic and Arctic inland waters with an emphasis on carbon cycling. [ABSTRACT FROM AUTHOR]

A combination of culture-dependent and culture-independent methodologies ( Bacteria and Archaea 16S rRNA gene clone library analyses) was used to determine the microbial diversity present within a geographically distinct high Arctic permafrost sample. Culturable Bacteria isolates, identified by 16S rRNA gene sequencing, belonged to the phyla Firmicutes, Actinobacteria and Proteobacteria with spore-forming Firmicutes being the most abundant; the majority of the isolates (19/23) were psychrotolerant, some (11/23) were halotolerant, and three isolates grew at −5°C. A Bacteria 16S rRNA gene library containing 101 clones was composed of 42 phylotypes related to diverse phylogenetic groups including the Actinobacteria, Proteobacteria, Firmicutes, Cytophaga – Flavobacteria – Bacteroides, Planctomyces and Gemmatimonadetes; the bacterial 16S rRNA gene phylotypes were dominated by Actinobacteria- and Proteobacteria-related sequences. An Archaea 16S rRNA gene clone library containing 56 clones was made up of 11 phylotypes and contained sequences related to both of the major Archaea domains ( Euryarchaeota and Crenarchaeota); the majority of sequences in the Archaea library were related to halophilic Archaea. Characterization of the microbial diversity existing within permafrost environments is important as it will lead to a better understanding of how microorganisms function and survive in such extreme cryoenvironments. [ABSTRACT FROM AUTHOR]

In a high Arctic polar semidesert ecosystem (ambient N deposition c. 0.1 g N m−2 a−1), the effects of N enrichment on the diversity of soil microfungi and on N content and availability in organic and mineral soils were determined. Three N (total: 0, 0.5, 5 g N m−2 a−1) and two P (total 0, 1 g m−2 a−1) treatments were applied, since P may limit response to N in this ecosystem. Organic and mineral soils were sampled in June and August in the second year of treatment for microfungi, pH, moisture content, and total N and P. In the third year, soils were resampled for extractable and total N and P. The fungi isolated were typical of high pH soils in the High Arctic and Antarctic. The species richness and diversity of soil microfungi were very low, with ranges as follows: Shannon diversity, 0.56–1.5; richness, 2–6; evenness, 0.79–0.9. There was no significant effect of treatment on the frequency of occurrence of different taxa of soil microfungi. Time of sampling also had no significant impact on fungal assemblages, although different, more diverse communities were isolated from organic, rather than mineral, soils. Nitrate-N in organic soil decreased significantly when P was added alone, but not when P and N were added together. Addition of 0.5 g N m−2 a−1, a rate deposition already occurring in Greenland and Iceland, appeared to exceed N demand even when P limitation was relieved. There was no apparent soil acidification as a result of the N treatments. [ABSTRACT FROM AUTHOR]

Bacterial biomass and functional diversity in four marine and four freshwater samples, collected from Resolute Bay, Nunavut, Canada, were studied using fluorescent nucleic-acid staining and sole-carbon-source utilization. Viable microbial counts using the LIVE/DEAD BacLight Viability Kit estimated viable marine bacterial numbers from 0.7 to 1.8×106 cells/l, which were lower than viable bacterial numbers in freshwater samples (2.1–9.9×106 cells/l) (RCBD-ANOVA). Calculations of the Shannon-Wiener diversity index and average well colour development were based on substrate utilization in ECO-Biolog plates incubated at 4°C and 20°C for 38 and 24 days, respectively. The Shannon-Wiener diversity of the marine water samples was significantly greater ( x H'=2.40±0.08, P <0.005; RCBD-ANOVA) than that of freshwater samples ( x H'=1.20±0.00, P <0.005; RCBD-ANOVA). Differences in microbial diversity between fresh and marine water samples at 4°C ( x 4°C =2.01) and 20°C (x20°C =2.31) were also detected by RCBD-ANOVA analysis. Interactions between water type and incubation temperature were not significant ( F =1.926, F c=5.12). Principal component analysis revealed differences in metabolic substrate utilization patterns and, consequently, the microbial diversity between water types and samples. [ABSTRACT FROM AUTHOR]

Microbial communities promptly respond to the environmental perturbations, especially in the Arctic and sub-Arctic systems that are highly impacted by climate change, and fluctuations in the diversity level of microbial assemblages could give insights on their expected response. 16S rRNA gene amplicon sequencing was applied to describe the bacterial community composition in water and sediment through the sub-Arctic Pasvik River. Our results showed that river water and sediment harbored distinct communities in terms of diversity and composition at genus level. The distribution of the bacterial communities was mainly affected by both salinity and temperature in sediment samples, and by oxygen in water samples. Glacial meltwaters and runoff waters from melting ice probably influenced the composition of the bacterial community at upper and middle river sites. Interestingly, marine-derived bacteria consistently accounted for a small proportion of the total sequences and were also more prominent in the inner part of the river. Results evidenced that particular conditions occurring at sampling sites (such as algal blooms, heavy metal contamination and anaerobiosis) may select species at local scale from a shared bacterial pool, thus favoring certain bacterial taxa. Conversely, the few phylotypes specifically detected in some sites are probably due to localized external inputs introducing allochthonous microbial groups. [ABSTRACT FROM AUTHOR]

The considerable microbial diversity of soils and key role in biogeochemical cycling have led to growing interest in their global distribution and the impact that environmental change might have at the regional level. In the broadest study of Arctic soil bacterial communities to date, we used high-throughput DNA sequencing to investigate the bacterial diversity from 200 independent Arctic soil samples from 43 sites. We quantified the impact of spatial and environmental factors on bacterial community structure using variation partitioning analysis, illustrating a nonrandom distribution across the region. pH was confirmed as the key environmental driver structuring Arctic soil bacterial communities, while total organic carbon (TOC), moisture and conductivity were shown to have little effect. Specialist taxa were more abundant in acidic and alkaline soils while generalist taxa were more abundant in acidoneutral soils. Of the 48 147 bacterial taxa, a core microbiome composed of only 13 taxa that were ubiquitously distributed and present within 95% of samples was identified, illustrating the high potential for endemism in the region. Overall, our results demonstrate the importance of spatial and edaphic factors on the structure of Arctic soil bacterial communities., (© FEMS 2019.)

Comparing the functional gene composition of soils at opposite extremes of environmental gradients may allow testing of hypotheses about community and ecosystem function. Here, we were interested in comparing how tropical microbial ecosystems differ from those of polar climates. We sampled several sites in the equatorial rainforest of Malaysia and Brunei, and the high Arctic of Svalbard, Canada, and Greenland, comparing the composition and the functional attributes of soil biota between the two extremes of latitude, using shotgun metagenomic Illumina HiSeq2000 sequencing. Based upon "classical" views of how tropical and higher latitude ecosystems differ, we made a series of predictions as to how various gene function categories would differ in relative abundance between tropical and polar environments. Results showed that in some respects our predictions were correct: the polar samples had higher relative abundance of dormancy related genes, and lower relative abundance of genes associated with respiration, and with metabolism of aromatic compounds. The network complexity of the Arctic was also lower than the tropics. However, in various other respects, the pattern was not as predicted; there were no differences in relative abundance of stress response genes or in genes associated with secondary metabolism. Conversely, CRISPR genes, phage-related genes, and virulence disease and defense genes, were unexpectedly more abundant in the Arctic, suggesting more intense biotic interaction. Also, eukaryote diversity and bacterial diversity were higher in the Arctic of Svalbard compared to tropical Brunei, which is consistent with what may expected from amplicon studies in terms of the higher pH of the Svalbard soil. Our results in some respects confirm expectations of how tropical versus polar nature may differ, and in other respects challenge them.

The Arctic Baffin Bay between Canada and Greenland is sea ice-covered during the majority of the year, restricting primary production to the summer months. Sediments receive low amounts of mostly terrestrial- and less marine-derived organic matter. To study microbial communities constrained by physicochemical conditions changing with distance from land and ocean depth, we applied high-throughput 16S rRNA gene sequencing and compared sequence diversity with biogeochemical parameters in 40 different sediment samples. Samples originated from seven cores down to 470 cm below seafloor along a shelf-to-basin transect. Bacterial diversity decreased faster with depth in basin than in shelf sediments, suggesting higher organic matter content sustained diversity into greater depths. All samples were dominated by Betaproteobacteria (mostly order Burkholderiales), which were especially abundant in basin sediments with low organic carbon and high Mn and Fe pore water concentrations. Strong statistical correlations between concentrations of reduced Mn and/or Fe and the relative abundances of Betaproteobacteria suggest that this group is involved in metal reduction in Baffin Bay sediments. Dehalococcoidia (phylum Chloroflexi) were abundant in all samples, especially in shelf sediments with high organic content. This study indicates that Mn and/or Fe play important roles structuring microbial communities in Arctic sediments poor in organic matter., (© FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The article presents a biogeographical study of soil microbial communities in the Arctic region. It mentions that researchers have analyzed genetic diversity among and within soil bacterial communities gathered from different locations across Arctic. The study shows that oil communities in Arctic are just as diverse as in temperate soils. It mentions that in spite of the harsh conditions soil microbial diversity flourishes in the Arctic.

Stamukhi lakes are vast but little-explored Arctic ecosystems. They occur throughout winter, spring, and early summer near large river inflows along the Arctic coastline, and are the result of freshwater retention behind the thick barrier of rubble ice (stamukhi) that forms at the outer limit of land-fast sea ice. We examined the molecular biodiversity within all three microbial domains (Bacteria, Archaea, and Eukaryota) and the heterotrophic productivity in Lake Mackenzie, a stamukhi lake in the western Canadian Arctic, and made comparative measurements in the freshwater (Mackenzie River) and marine (Beaufort Sea) source waters. Bacterial and eukaryotic communities in the stamukhi lake differed in composition and diversity from both marine and riverine environments, whereas the archaeal communities were similar in the lake and river. Bacteria 16S ribosomal RNA sequences from the lake were mostly within freshwater clusters of Betaproteobacteria and Bacteroidetes and the Archaea were within the Lake Dagow sediment and Rice cluster-V clusters of Euryarchaeota. The eukaryotes were mainly ciliates from the subclass Choreotrichia, and there was a notable lack of flagellates. Heterotrophic production rates in the lake were lower than in the river and more similar to those in the sea, despite much higher bacterial concentrations than in either. The lake samples had markedly higher ratios of ³H leucine to ³H thymidine incorporation than in the river and sea, implying some physiological stress. Lake Mackenzie is an active microbial ecosystem with distinct physical and microbiological properties. This circumpolar ecosystem type, vulnerable to the ongoing effects of climate change, likely plays a key functional role in processing riverine inputs to the Arctic Ocean. [ABSTRACT FROM AUTHOR]