Search

Global warming-induced sea ice loss in the Canadian Northwest Passage (NWP) will result in more shipping traffic, increasing the risk of oil spills. Microorganisms inhabiting NWP beach sediments may degrade hydrocarbons, offering a potential bioremediation strategy. In this study, the characterization and genomic analyses of 22 hydrocarbon-biodegradative bacterial isolates revealed that they contained a diverse range of key alkane and aromatic hydrocarbon-degradative genes, as well as cold and salt tolerance genes indicating they are highly adapted to the extreme Arctic environment. Some isolates successfully degraded Ultra Low Sulfur Fuel Oil (ULSFO) at temperatures as low as -5 °C and high salinities (3%-10%). Three isolates were grown in liquid medium containing ULSFO as sole carbon source over 3 months and variation of hydrocarbon concentration was measured at three time points to determine their rate of hydrocarbon biodegradation. Our results demonstrate that two isolates ( Rhodococcus sp. R1B_2T and Pseudarthrobacter sp. R2D_1T) possess complete degradation pathways and can grow on alkane and aromatic components of ULSFO under Arctic conditions. Overall, these results demonstrate that diverse hydrocarbon-degrading microorganisms exist in the NWP beach sediments, offering a potential bioremediation strategy in the events of a marine fuel spill reaching the shores of the NWP., Competing Interests: The authors declare no conflict of interest.

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The extent of fractionation of sulfur isotopes by sulfate-reducing microbes is dictated by genomic and environmental factors. A greater understanding of species-specific fractionations may better inform interpretation of sulfur isotopes preserved in the rock record. To examine whether gene diversity influences net isotopic fractionation in situ, we assessed environmental chemistry, sulfate reduction rates, diversity of putative sulfur-metabolizing organisms by 16S rRNA and dissimilatory sulfite reductase (dsrB) gene amplicon sequencing, and net fractionation of sulfur isotopes along a sediment transect of a hypersaline Arctic spring. In situ sulfate reduction rates yielded minimum cell-specific sulfate reduction rates < 0.3 × 10 -15 moles cell -1  day -1 . Neither 16S rRNA nor dsrB diversity indices correlated with relatively constant (38‰-45‰) net isotope fractionation (ε 34 S sulfide-sulfate ). Measured ε 34 S values could be reproduced in a mechanistic fractionation model if 1%-2% of the microbial community (10%-60% of Deltaproteobacteria) were engaged in sulfate respiration, indicating heterogeneous respiratory activity within sulfate-reducing populations. This model indicated enzymatic kinetic diversity of Apr was more likely to correlate with sulfur fractionation than DsrB. We propose that, above a threshold Shannon diversity value of 0.8 for dsrB, the influence of the specific composition of the microbial community responsible for generating an isotope signal is overprinted by the control exerted by environmental variables on microbial physiology., (© 2019 John Wiley & Sons Ltd.)

Microbial metabolism of the thawing organic carbon stores in permafrost results in a positive feedback loop of greenhouse gas emissions. CO 2 and CH 4 fluxes and the associated microbial communities in Arctic cryosols are important in predicting future warming potential of the Arctic. We demonstrate that topography had an impact on CH 4 and CO 2 flux at a high Arctic ice-wedge polygon terrain site, with higher CO 2 emissions and lower CH 4 uptake at troughs compared to polygon interior soils. The pmoA sequencing suggested that USCα cluster of uncultured methanotrophs is likely responsible for observed methane sink. Community profiling revealed distinct assemblages across the terrain at different depths. Deeper soils contained higher abundances of Verrucomicrobia and Gemmatimonadetes, whereas the polygon interior had higher Acidobacteria and lower Betaproteobacteria and Deltaproteobacteria abundances. Genome sequencing of isolates from the terrain revealed presence of carbon cycling genes including ones involved in serine and ribulose monophosphate pathways. A novel hybrid network analysis identified key members that had positive and negative impacts on other species. Operational Taxonomic Units (OTUs) with numerous positive interactions corresponded to Proteobacteria, Candidatus Rokubacteria and Actinobacteria phyla, while Verrucomicrobia and Acidobacteria members had negative impacts on other species. Results indicate that topography and microbial interactions impact community composition., (© 2019 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Water tracks in the Antarctic Dry Valleys are dark linear features of increased soil moisture that flow downslope over the spring and summer, providing a source of moisture in a cold-arid desert. They are typically sourced from melting snow, ground ice, and deliquescence (Levy et al. , 2011 ). This research presents the first in-depth study of the activity potential and diversity of microbial communities of Antarctic water tracks. We investigated whether these water track soils are more habitable to microbial communities by ascertaining the differences in diversity, total and culturable cell counts, and microbial respiratory activity in water track soils compared with the adjacent dry soils in Pearse Valley. Total cell counts ranged from 1.47 × 10 3 to 4.17 × 10 5 cells/g dry weight soil. Water track soils had higher total and culturable biomass, in addition to higher microbial activity at 5° and -5°C, compared with adjacent dry soils. Microbial respiration was positively correlated with soil moisture content, but total cell counts and plate counts were not. Surprisingly, microbial community composition did not differ between wet and dry soil communities, and was not related to soil moisture content. The microbial community composition instead appeared to differ spatially based on location and depth. Overall, the data suggest that cold water tracks are more habitable than the surrounding cold-arid soils. Our results suggest that recurring slope lineae, which are dark linear features that grow downslope on Mars over the spring and summer, where liquid water might be a recurring phenomenon, could be sites of astrobiological potential.

Permafrost accounts for 27% of all soil ecosystems and harbors diverse microbial communities. Our understanding of microorganisms in permafrost, their activities and adaptations, remains limited. Using five subzero-growing (cryophilic) permafrost bacteria, we examined features of cold adaptation through comparative genomic analyses with mesophilic relatives. The cryophiles possess genes associated with cold adaptation, including cold shock proteins, RNA helicases, and oxidative stress and carotenoid synthesis enzymes. Higher abundances of genes associated with compatible solutes were observed, important for osmoregulation in permafrost brine veins. Most cryophiles in our study have higher transposase copy numbers than mesophiles. We investigated amino acid (AA) modifications in the cryophiles favoring increased protein flexibility at cold temperatures. Although overall there were few differences with the mesophiles, we found evidence of cold adaptation, with significant differences in proline, serine, glycine and aromaticity, in several cryophiles. The use of cold/hot AA ratios of >1, used in previous studies to indicate cold adaptation, was found to be inadequate on its own. Comparing the average of all cryophiles to all mesophiles, we found that overall cryophiles had a higher ratio of cold adapted proteins for serine (more serine), and to a lesser extent, proline and acidic residues (fewer prolines/acidic residues).

The lost hammer (LH) spring perennially discharges subzero hypersaline reducing brines through thick layers of permafrost and is the only known terrestrial methane seep in frozen settings on Earth. The present study aimed to identify active microbial communities that populate the sediments of the spring outlet, and verify whether such communities vary seasonally and spatially. Microcosm experiments revealed that the biological reduction of sulfur compounds (SR) with hydrogen (e.g., sulfate reduction) was potentially carried out under combined hypersaline and subzero conditions, down to -20 °C, the coldest temperature ever recorded for SR. Pyrosequencing analyses of both 16S rRNA (i.e., cDNA) and 16S rRNA genes (i.e., DNA) of sediments retrieved in late winter and summer indicated fairly stable bacterial and archaeal communities at the phylum level. Potentially active bacterial and archaeal communities were dominated by clades related to the T78 Chloroflexi group and Halobacteria species, respectively. The present study indicated that SR, hydrogenotrophy (possibly coupled to autotrophy), and short-chain alkane degradation (other than methane), most likely represent important, previously unaccounted for, metabolic processes carried out by LH microbial communities. Overall, the obtained findings provided additional evidence that the LH system hosts active communities of anaerobic, halophilic, and cryophilic microorganisms despite the extreme conditions in situ.

Increased exploration and exploitation of resources in the Arctic is leading to a higher risk of petroleum contamination. A number of Arctic microorganisms can use petroleum for growth-supporting carbon and energy, but traditional approaches for stimulating these microorganisms (for example, nutrient addition) have varied in effectiveness between sites. Consistent environmental controls on microbial community response to disturbance from petroleum contaminants and nutrient amendments across Arctic soils have not been identified, nor is it known whether specific taxa are universally associated with efficient bioremediation. In this study, we contaminated 18 Arctic soils with diesel and treated subsamples of each with monoammonium phosphate (MAP), which has successfully stimulated degradation in some contaminated Arctic soils. Bacterial community composition of uncontaminated, diesel-contaminated and diesel+MAP soils was assessed through multiplexed 16S (ribosomal RNA) rRNA gene sequencing on an Ion Torrent Personal Genome Machine, while hydrocarbon degradation was measured by gas chromatography analysis. Diversity of 16S rRNA gene sequences was reduced by diesel, and more so by the combination of diesel and MAP. Actinobacteria dominated uncontaminated soils with <10% organic matter, while Proteobacteria dominated higher-organic matter soils, and this pattern was exaggerated following disturbance. Degradation with and without MAP was predictable by initial bacterial diversity and the abundance of specific assemblages of Betaproteobacteria, respectively. High Betaproteobacteria abundance was positively correlated with high diesel degradation in MAP-treated soils, suggesting this may be an important group to stimulate. The predictability with which bacterial communities respond to these disturbances suggests that costly and time-consuming contaminated site assessments may not be necessary in the future.

Lost Hammer (LH) spring is a unique hypersaline, subzero, perennial high Arctic spring arising through thick permafrost. In the present study, the microbial and geochemical characteristics of the LH outflow channels, which remain unfrozen at ≥-18°C and are more aerobic/less reducing than the spring source were examined and compared to the previously characterized spring source environment. LH channel sediments contained greater microbial biomass (~100-fold) and greater microbial diversity reflected by the 16S rRNA clone libraries. Phylotypes related to methanogenesis, methanotrophy, sulfur reduction and oxidation were detected in the bacterial clone libraries while the archaeal community was dominated by phylotypes most closely related to THE ammonia-oxidizing Thaumarchaeota. The cumulative percent recovery of (14)C-acetate mineralization in channel sediment microcosms exceeded ~30% and ~10% at 5 and -5°C, respectively, but sharply decreased at -10°C (≤1%). Most bacterial isolates (Marinobacter, Planococcus, and Nesterenkonia spp.) were psychrotrophic, halotolerant, and capable of growth at -5°C. Overall, the hypersaline, subzero LH spring channel has higher microbial diversity and activity than the source, and supports a variety of niches reflecting the more dynamic and heterogeneous channel environment.

Produced water is one of the largest waste products routinely discharged into the ocean from offshore oil and gas platforms. This study analyzed bacterial communities and metals in the produced water, surrounding seawater, and sediment around the Thebaud platform. The bacterial community within the produced water was different from the seawater (SAB=13.3), but the discharge had no detectable effect on the bacterial communities in the seawater (SAB>97). In contrast, genomic analysis of sediments revealed that the bacterial community from 250 m was different (SAB=70) from other locations further from the discharge, suggesting that the produced water had a detectable effect on the bacterial community in the sediment closest to the discharge. These near-field sediments contained elevated concentrations of manganese and iron that are associated with the produced water effluent. The results suggested that the discharge of produced water has influenced the bacterial community structure of sediments adjacent to the platform., (Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.)

Arctic soils are increasingly susceptible to petroleum hydrocarbon contamination, as exploration and exploitation of the Arctic increase. Bioremediation in these soils is challenging due to logistical constraints and because soil temperatures only rise above 0°C for ∼2 months each year. Nitrogen is often added to contaminated soil in situ to stimulate the existing microbial community, but little is known about how the added nutrients are used by these microorganisms. Microbes vary widely in their ability to metabolize petroleum hydrocarbons, so the question becomes: which hydrocarbon-degrading microorganisms most effectively use this added nitrogen for growth? Using [(15)N]DNA-based stable isotope probing, we determined which taxonomic groups most readily incorporated nitrogen from the monoammonium phosphate added to contaminated and uncontaminated soil in Canadian Forces Station-Alert, Nunavut, Canada. Fractions from each sample were amplified with bacterial 16S rRNA and alkane monooxygenase B (alkB) gene-specific primers and then sequenced using large-scale parallel-pyrosequencing. Sequence data was combined with 16S rRNA and alkB gene C quantitative PCR data to measure the presence of various phylogenetic groups in fractions at different buoyant densities. Several families of Proteobacteria and Actinobacteria that are directly involved in petroleum degradation incorporated the added nitrogen in contaminated soils, but it was the DNA of Sphingomonadaceae that was most enriched in (15)N. Bacterial growth in uncontaminated soils was not stimulated by nutrient amendment. Our results suggest that nitrogen uptake efficiency differs between bacterial groups in contaminated soils. A better understanding of how groups of hydrocarbon-degraders contribute to the catabolism of petroleum will facilitate the design of more targeted bioremediation treatments.

The abundance and structure of archaeal and bacterial communities from the active layer and the associated permafrost of a moderately acidic (pH < 5.0) High Arctic wetland (Axel Heiberg Island, Nunavut, Canada) were investigated using culture- and molecular-based methods. Aerobic viable cell counts from the active layer were ∼100-fold greater than those from the permafrost (2.5 × 10(5) CFU·(g soil dry mass)(-1)); however, a greater diversity of isolates were cultured from permafrost, as determined by 16S rRNA gene sequencing. Isolates from both layers demonstrated growth characteristics of a psychrotolerant, halotolerant, and acidotolerant community. Archaea constituted 0.1% of the total 16S rRNA gene copy number and, in the 16S rRNA gene clone library, predominantly (71% and 95%) consisted of Crenarchaeota related to Group I. 1b. In contrast, bacterial communities were diverse (Shannon's diversity index, H = ∼4), with Acidobacteria constituting the largest division of active layer clones (30%) and Actinobacteria most abundant in permafrost (28%). Direct comparisons of 16S rRNA gene sequence data highlighted significant differences between the bacterial communities of each layer, with the greatest differences occurring within Actinobacteria. Comparisons of 16S rRNA gene sequences with those from other Arctic permafrost and cold-temperature wetlands revealed commonly occurring taxa within the phyla Chloroflexi, Acidobacteria, and Actinobacteria (families Intrasporangiaceae and Rubrobacteraceae).

We report the first microbiological characterization of a terrestrial methane seep in a cryo-environment in the form of an Arctic hypersaline (∼24% salinity), subzero (-5 °C), perennial spring, arising through thick permafrost in an area with an average annual air temperature of -15 °C. Bacterial and archaeal 16S rRNA gene clone libraries indicated a relatively low diversity of phylotypes within the spring sediment (Shannon index values of 1.65 and 1.39, respectively). Bacterial phylotypes were related to microorganisms such as Loktanella, Gillisia, Halomonas and Marinobacter spp. previously recovered from cold, saline habitats. A proportion of the bacterial phylotypes were cultured, including Marinobacter and Halomonas, with all isolates capable of growth at the in situ temperature (-5 °C). Archaeal phylotypes were related to signatures from hypersaline deep-sea methane-seep sediments and were dominated by the anaerobic methane group 1a (ANME-1a) clade of anaerobic methane oxidizing archaea. CARD-FISH analyses indicated that cells within the spring sediment consisted of ∼84.0% bacterial and 3.8% archaeal cells with ANME-1 cells accounting for most of the archaeal cells. The major gas discharging from the spring was methane (∼50%) with the low CH(4)/C(2+) ratio and hydrogen and carbon isotope signatures consistent with a thermogenic origin of the methane. Overall, this hypersaline, subzero environment supports a viable microbial community capable of activity at in situ temperature and where methane may behave as an energy and carbon source for sustaining anaerobic oxidation of methane-based microbial metabolism. This site also provides a model of how a methane seep can form in a cryo-environment as well as a mechanism for the hypothesized Martian methane plumes.

The melting of permafrost and its potential impact on CH(4) emissions are major concerns in the context of global warming. Methanotrophic bacteria have the capacity to mitigate CH(4) emissions from melting permafrost. Here, we used quantitative PCR (qPCR), stable isotope probing (SIP) of DNA, denaturing gradient gel electrophoresis (DGGE) fingerprinting, and sequencing of the 16S rRNA and pmoA genes to study the activity and diversity of methanotrophic bacteria in active-layer soils from Ellesmere Island in the Canadian high Arctic. Results showed that most of the soils had the capacity to oxidize CH(4) at 4 degrees C and at room temperature (RT), but the oxidation rates were greater at RT than at 4 degrees C and were significantly enhanced by nutrient amendment. The DGGE banding patterns associated with active methanotrophic bacterial populations were also different depending on the temperature of incubation and the addition of nutrients. Sequencing of the 16S rRNA and pmoA genes indicated a low diversity of the active methanotrophic bacteria, with all methanotroph 16S rRNA and pmoA gene sequences being related to type I methanotrophs from Methylobacter and Methylosarcina. The dominance of type I methanotrophs over type II methanotrophs in the native soil samples was confirmed by qPCR of the 16S rRNA gene with primers specific for these two groups of bacteria. The 16S rRNA and pmoA gene sequences related to those of Methylobacter tundripaludum were found in all soils, regardless of the incubation conditions, and they might therefore play a role in CH(4) degradation in situ. This work is providing new information supporting the potential importance of Methylobacter spp. in Arctic soils found in previous studies and contributes to the limited body of knowledge on methanotrophic activity and diversity in this extreme environment.

The Gully is the first Fisheries and Oceans Canada marine protected area off the eastern coast of Canada. To ensure success of conservation efforts in this area, it is essential to develop a better understanding of microbial community composition from the euphotic zone to the deep sea in this previously unsurveyed environment. Denaturing gradient gel electrophoresis (DGGE) and nucleotide sequencing were used to characterize microbial community structure. DGGE results showed a clear difference in the microbial community structure between the euphotic zone and the deep sea water. Cluster analysis showed high similarity (>85%) for all the samples taken from below 500 m, but lower similarity (49%-72%) when comparing samples from above and below 500 m. Changes in microbial community structure with depth corresponded well with changes in oceanographic physical parameters. Furthermore, 16S rRNA gene analysis showed that the bacterioplankton sequences generally clustered into 1 of 9 major lineages commonly found in marine systems. However, not all the major lineages were detected at all the different depths. The SAR11 and SAR116 sequences were only present in the surface water, and the SAR324 and Actinobacteria sequences were only present in deep sea water. These findings provide a preliminary characterization of the microbial communities of this unique ecosystem.

High-Arctic soils have low nutrient availability, low moisture content, and very low temperatures and, as such, they pose a particular problem in terms of hydrocarbon bioremediation. An in-depth knowledge of the microbiology involved in this process is likely to be crucial to understand and optimize the factors most influencing bioremediation. Here, we compared two distinct large-scale field bioremediation experiments, located at the Canadian high-Arctic stations of Alert (ex situ approach) and Eureka (in situ approach). Bacterial community structure and function were assessed using microarrays targeting the 16S rRNA genes of bacteria found in cold environments and hydrocarbon degradation genes as well as quantitative reverse transcriptase PCR targeting key functional genes. The results indicated a large difference between sampling sites in terms of both soil microbiology and decontamination rates. A rapid reorganization of the bacterial community structure and functional potential as well as rapid increases in the expression of alkane monooxygenases and polyaromatic hydrocarbon-ring-hydroxylating dioxygenases were observed 1 month after the bioremediation treatment commenced in the Alert soils. In contrast, no clear changes in community structure were observed in Eureka soils, while key gene expression increased after a relatively long lag period (1 year). Such discrepancies are likely caused by differences in bioremediation treatments (i.e., ex situ versus in situ), weathering of the hydrocarbons, indigenous microbial communities, and environmental factors such as soil humidity and temperature. In addition, this study demonstrates the value of molecular tools for the monitoring of polar bacteria and their associated functions during bioremediation.

Culture-dependent and culture-independent methods were used in an investigation of the microbial diversity in a permafrost/massive ground ice core from the Canadian high Arctic. Denaturing gradient gel electrophoresis as well as Bacteria and Archaea 16S rRNA gene clone libraries showed differences in the composition of the microbial communities in the distinct core horizons. Microbial diversity was similar in the active layer (surface) soil, permafrost table and permafrost horizons while the ground ice microbial community showed low diversity. Bacteria and Archaea sequences related to the Actinobacteria (54%) and Crenarchaeota (100%) respectively were predominant in the active layer while the majority of sequences in the permafrost were related to the Proteobacteria (57%) and Euryarchaeota (76%). The most abundant phyla in the ground ice clone libraries were the Firmicutes (59%) and Crenarchaeota (82%). Isolates from the permafrost were both less abundant and diverse than in the active layer soil, while no culturable cells were recovered from the ground ice. Mineralization of [1-(14)C] acetic acid and [2-(14)C] glucose was used to detect microbial activity in the different horizons in the core. Mineralization was detected at near ambient permafrost temperatures (-15 degrees C), indicating that permafrost may harbour an active microbial population, while the low microbial diversity, abundance and activity in ground ice suggests a less hospitable microbial habitat.

The saline springs of Gypsum Hill in the Canadian high Arctic are a rare example of cold springs originating from deep groundwater and rising to the surface through thick permafrost. The heterotrophic bacteria and autotrophic sulfur-oxidizing bacteria (up to 40% of the total microbial community) isolated from the spring waters and sediments were classified into four phyla (Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria) based on 16S rRNA gene analysis; heterotrophic isolates were primarily psychrotolerant, salt-tolerant, facultative anaerobes. Some of the isolates contained genes for thiosulfate oxidation (soxB) and anoxygenic photosynthesis (pufM), possibly enabling the strains to better compete in these sulfur-rich environments subject to long periods of illumination in the Arctic summer. Although leucine uptake by the spring water microbial community was low, CO(2) uptake was relatively high under dark incubation, reinforcing the idea that primary production by chemoautotrophs is an important process in the springs. The small amounts of hydrocarbons in gases exsolving from the springs (0.38 to 0.51% CH(4)) were compositionally and isotopically consistent with microbial methanogenesis and possible methanotrophy. Anaerobic heterotrophic sulfur oxidation and aerobic autotrophic sulfur oxidation activities were demonstrated in sediment slurries. Overall, our results describe an active microbial community capable of sustainability in an extreme environment that experiences prolonged periods of continuous light or darkness, low temperatures, and moderate salinity, where life seems to rely on chemolithoautotrophy.

The prokaryotic diversity and respiratory activity of microbial mat communities on the Markham Ice Shelf and Ward Hunt Ice Shelf in the Canadian high Arctic were analysed. All heterotrophic isolates and > 95% of bacterial 16S rRNA gene clone library sequences from both ice shelves grouped within the phyla Bacteroidetes, Proteobacteria and Actinobacteria. Clone library analyses showed that the bacterial communities were diverse and varied significantly between the two ice shelves, with the Markham library having a higher estimated diversity (Chao1 = 243; 105 operational taxonomic units observed in 189 clones) than the Ward Hunt library (Chao1 = 106; 52 operational taxonomic units observed in 128 clones). Archaeal 16S rRNA gene clone libraries from both ice shelves were dominated by a single Euryarchaeota sequence, which appears to represent a novel phylotype. Analyses of community activity by radiorespiration assays detected metabolism in mat samples from both ice shelves at temperatures as low as -10 degrees C. These findings provide the first insight into the prokaryotic biodiversity of Arctic ice shelf communities and underscore the importance of these cryo-ecosystems as a rich source of microbiota that are adapted to extreme cold.

The springs at Gypsum Hill and Colour Peak on Axel Heiberg Island in the Canadian Arctic originate from deep salt aquifers and are among the few known examples of cold springs in thick permafrost on Earth. The springs discharge cold anoxic brines (7.5 to 15.8% salts), with a mean oxidoreduction potential of -325 mV, and contain high concentrations of sulfate and sulfide. We surveyed the microbial diversity in the sediments of seven springs by denaturing gradient gel electrophoresis (DGGE) and analyzing clone libraries of 16S rRNA genes amplified with Bacteria and Archaea-specific primers. Dendrogram analysis of the DGGE banding patterns divided the springs into two clusters based on their geographic origin. Bacterial 16S rRNA clone sequences from the Gypsum Hill library (spring GH-4) were classified into seven phyla (Actinobacteria, Bacteroidetes, Firmicutes, Gemmatimonadetes, Proteobacteria, Spirochaetes, and Verrucomicrobia); Deltaproteobacteria and Gammaproteobacteria sequences represented half of the clone library. Sequences related to Proteobacteria (82%), Firmicutes (9%), and Bacteroidetes (6%) constituted 97% of the bacterial clone library from Colour Peak (spring CP-1). Most GH-4 archaeal clone sequences (79%) were related to the Crenarchaeota while half of the CP-1 sequences were related to orders Halobacteriales and Methanosarcinales of the Euryarchaeota. Sequences related to the sulfur-oxidizing bacterium Thiomicrospira psychrophila dominated both the GH-4 (19%) and CP-1 (45%) bacterial libraries, and 56 to 76% of the bacterial sequences were from potential sulfur-metabolizing bacteria. These results suggest that the utilization and cycling of sulfur compounds may play a major role in the energy production and maintenance of microbial communities in these unique, cold environments.

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 degrees 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.

Permafrost represents 26% of terrestrial soil ecosystems; yet its biology, essentially microbiology, remains relatively unexplored. The permafrost environment is considered extreme because indigenous microorganisms must survive prolonged exposure to subzero temperatures and background radiation for geological time scales in a habitat with low water activity and extremely low rates of nutrient and metabolite transfer. Yet considerable numbers and biodiversity of bacteria exist in permafrost, some of which may be among the most ancient viable life on Earth. This review describes the permafrost environment as a microbial habitat and reviews recent studies examining microbial biodiversity found in permafrost as well as microbial growth and activity at ambient in situ subzero temperatures. These investigations suggest that functional microbial ecosystems exist within the permafrost environment and may have important implications on global biogeochemical processes as well as the search for past or extant life in permafrost presumably present on Mars and other bodies in our solar system.

Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM) fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal) alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI), and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS) region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas), metal sequestration (Brevundimonas and Caulobacter) and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas) increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN) assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude) and mineralization (five-fold). Genomic techniques proved useful in investigating tripartite (plant-bacteria-fungi) interactions during phytostabilization, contributing to our knowledge in this field of study. [ABSTRACT FROM AUTHOR]

Intermicrobial competition is known to occur in many natural environments, and can result from direct conflict between organisms, or from differential rates of growth, colonization, and/or nutrient acquisition. It has been difficult to extensively examine intermicrobial competition in situ, but these interactions may play an important role in the regulation of the many biogeochemical processes that are tied to microbial communities in polar soils. A greater understanding of how competition influences productivity will improve projections of gas and nutrient flux as the poles warm, may provide biotechnological opportunities for increasing the degradation of contaminants in polar soil, and will help to predict changes in communities of higher organisms, such as plants. [ABSTRACT FROM AUTHOR]

Reports on the selection of specific endophytic bacterial genotypes by plants in response to soil contamination. Effect of the addition of petroleum to sediment; Plant and contaminant dependence of the enrichment of catabolic genotypes in the root interior.