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1.
Sci Data ; 8(1): 221, 2021 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-34413318

RESUMO

Thermokarst activity at permafrost sites releases considerable amounts of ancient carbon to the atmosphere. A large part of this carbon is released via thermokarst ponds, and fungi could be an important organismal group enabling its recycling. However, our knowledge about aquatic fungi in thermokarstic systems is extremely limited. In this study, we collected samples from five permafrost sites distributed across circumpolar Arctic and representing different stages of permafrost integrity. Surface water samples were taken from the ponds and, additionally, for most of the ponds also the detritus and sediment samples were taken. All the samples were extracted for total DNA, which was then amplified for the fungal ITS2 region of the ribosomal genes. These amplicons were sequenced using PacBio technology. Water samples were also collected to analyze the chemical conditions in the ponds, including nutrient status and the quality and quantity of dissolved organic carbon. This dataset gives a unique overview of the impact of the thawing permafrost on fungal communities and their potential role on carbon recycling.


Assuntos
Fungos/classificação , Micobioma , Pergelissolo/microbiologia , Lagoas/microbiologia , Regiões Árticas , Código de Barras de DNA Taxonômico , DNA Fúngico/genética , DNA Fúngico/isolamento & purificação , DNA Espaçador Ribossômico/genética , Congelamento , Fungos/genética , Fungos/isolamento & purificação , Lagoas/química
2.
Appl Environ Microbiol ; 87(20): e0133921, 2021 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-34347514

RESUMO

Permafrost soils store approximately twice the amount of carbon currently present in Earth's atmosphere and are acutely impacted by climate change due to the polar amplification of increasing global temperature. Many organic-rich permafrost sediments are located on large river floodplains, where river channel migration periodically erodes and redeposits the upper tens of meters of sediment. Channel migration exerts a first-order control on the geographic distribution of permafrost and floodplain stratigraphy and thus may affect microbial habitats. To examine how river channel migration in discontinuous permafrost environments affects microbial community composition, we used amplicon sequencing of the 16S rRNA gene on sediment samples from floodplain cores and exposed riverbanks along the Koyukuk River, a large tributary of the Yukon River in west-central Alaska. Microbial communities are sensitive to permafrost thaw: communities found in deep samples thawed by the river closely resembled near-surface active-layer communities in nonmetric multidimensional scaling analyses but did not resemble floodplain permafrost communities at the same depth. Microbial communities also displayed lower diversity and evenness in permafrost than in both the active layer and permafrost-free point bars recently deposited by river channel migration. Taxonomic assignments based on 16S and quantitative PCR for the methyl coenzyme M reductase functional gene demonstrated that methanogens and methanotrophs are abundant in older permafrost-bearing deposits but not in younger, nonpermafrost point bar deposits. The results suggested that river migration, which regulates the distribution of permafrost, also modulates the distribution of microbes potentially capable of producing and consuming methane on the Koyukuk River floodplain. IMPORTANCE Arctic lowlands contain large quantities of soil organic carbon that is currently sequestered in permafrost. With rising temperatures, permafrost thaw may allow this carbon to be consumed by microbial communities and released to the atmosphere as carbon dioxide or methane. We used gene sequencing to determine the microbial communities present in the floodplain of a river running through discontinuous permafrost. We found that the river's lateral movement across its floodplain influences the occurrence of certain microbial communities-in particular, methane-cycling microbes were present on the older, permafrost-bearing eroding riverbank but absent on the newly deposited river bars. Riverbank sediment had microbial communities more similar to those of the floodplain active-layer samples than permafrost samples from the same depth. Therefore, spatial patterns of river migration influence the distribution of microbial taxa relevant to the warming Arctic climate.


Assuntos
Microbiota , Pergelissolo/microbiologia , Rios/microbiologia , Alaska , Ciclo do Carbono , Movimentos da Água
3.
Appl Environ Microbiol ; 87(19): e0097221, 2021 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-34288700

RESUMO

Permafrost microbes may be metabolically active in microscopic layers of liquid brines, even in ancient soil. Metagenomics can help discern whether permafrost microbes show adaptations to this environment. Thirty-three metagenome-assembled genomes (MAGs) were obtained from six depths (3.5 m to 20 m) of freshly cored permafrost from the Siberian Kolyma-Indigirka Lowland region. These soils have been continuously frozen for ∼20,000 to 1,000,000 years. Eight of these MAGs were ≥80% complete with <10% contamination and were taxonomically identified as Aminicenantes, Atribacteria, Chloroflexi, and Actinobacteria within bacteria and Thermoprofundales within archaea. MAGs from these taxa have been obtained previously from nonpermafrost environments and have been suggested to show adaptations to long-term energy starvation, but they have never been explored in ancient permafrost. The permafrost MAGs had greater proportions in the Clusters of Orthologous Groups (COGs) categories of energy production and conversion and carbohydrate transport and metabolism than did their nonpermafrost counterparts. They also contained genes for trehalose synthesis, thymine metabolism, mevalonate biosynthesis, and cellulose degradation, which were less prevalent in nonpermafrost genomes. Many of these genes are involved in membrane stabilization and osmotic stress responses, consistent with adaptation to the anoxic, high-ionic-strength, cold environments of permafrost brine films. Our results suggest that this ancient permafrost contains DNA of high enough quality to assemble MAGs from microorganisms with adaptations to survive long-term freezing in this extreme environment. IMPORTANCE Permafrost around the world is thawing rapidly. Many scientists from a variety of disciplines have shown the importance of understanding what will happen to our ecosystem, commerce, and climate when permafrost thaws. The fate of permafrost microorganisms is connected to these predicted rapid environmental changes. Studying ancient permafrost with culture-independent techniques can give a glimpse into how these microorganisms function under these extreme low-temperature and low-energy conditions. This will facilitate understanding how they will change with the environment. This study presents genomic data from this unique environment ∼20,000 to 1,000,000 years of age.


Assuntos
Metagenoma , Pergelissolo/microbiologia , Adaptação Fisiológica , Sibéria
5.
Microb Genom ; 7(4)2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33848236

RESUMO

The warming-induced thawing of permafrost promotes microbial activity, often resulting in enhanced greenhouse gas emissions. The ability of permafrost microorganisms to survive the in situ sub-zero temperatures, their energetic strategies and their metabolic versatility in using soil organic materials determine their growth and functionality upon thawing. Hence, functional characterization of the permafrost microbiome, particularly in the underexplored mid-latitudinal alpine regions, is a crucial first step in predicting its responses to the changing climate, and the consequences for soil-climate feedbacks. In this study, for the first time, the functional potential and metabolic capabilities of a temperate mountain permafrost microbiome from central Europe has been analysed using shotgun metagenomics. Permafrost and active layers from the summit of Muot da Barba Peider (MBP) [Swiss Alps, 2979 m above sea level (a.s.l.)] revealed a strikingly high functional diversity in the permafrost (north-facing soils at a depth of 160 cm). Permafrost metagenomes were enriched in stress-response genes (e.g. cold-shock genes, chaperones), as well as in genes involved in cell defence and competition (e.g. antiviral proteins, antibiotics, motility, nutrient-uptake ABC transporters), compared with active-layer metagenomes. Permafrost also showed a higher potential for the synthesis of carbohydrate-active enzymes, and an overrepresentation of genes involved in fermentation, carbon fixation, denitrification and nitrogen reduction reactions. Collectively, these findings demonstrate the potential capabilities of permafrost microorganisms to thrive in cold and oligotrophic conditions, and highlight their metabolic versatility in carbon and nitrogen cycling. Our study provides a first insight into the high functional gene diversity of the central European mountain permafrost microbiome. Our findings extend our understanding of the microbial ecology of permafrost and represent a baseline for future investigations comparing the functional profiles of permafrost microbial communities at different latitudes.


Assuntos
Bactérias/genética , Bactérias/metabolismo , Microbiota , Pergelissolo/microbiologia , Bactérias/classificação , Bactérias/isolamento & purificação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Carbono/metabolismo , Ciclo do Carbono , Metagenoma , Metagenômica , Nitrogênio/metabolismo , Pergelissolo/química , Filogenia , Microbiologia do Solo , Suíça
7.
Astrobiology ; 20(6): 754-765, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32525738

RESUMO

Microbial ecology of permafrost, due to its ecological and astrobiological importance, has been in the focus of studies in past decades. Although permafrost is an ancient and stable environment, it is also subjected to current climate changes. Permafrost degradation often results in generation of thaw ponds, a phenomenon not only reported mainly from polar regions but also present in high-altitude permafrost environments. Our knowledge about microbial communities of thaw ponds in these unique, remote mountain habitats is sparse. This study presents the first culture collection and results of the next-generation DNA sequencing (NGS) analysis of bacterial communities inhabiting a high-altitude permafrost thaw pond. In February 2016, a permafrost thaw pond on the Ojos del Salado at 5900 m a.s.l. (meters above sea level) was sampled as part of the Hungarian Dry Andes Research Programme. A culture collection of 125 isolates was established, containing altogether 11 genera belonging to phyla Bacteroidetes, Actinobacteria, and Proteobacteria. Simplified bacterial communities with a high proportion of candidate and hitherto uncultured bacteria were revealed by Illumina MiSeq NGS. Water of the thaw pond was dominated by Bacteroidetes and Proteobacteria, while in the sediment of the lake and permafrost, members of Acidobacteria, Actinobacteria, Bacteroidetes, Patescibacteria, Proteobacteria, and Verrucomicrobia were abundant. This permafrost habitat can be interesting as a potential Mars analog.


Assuntos
Altitude , Bactérias/genética , Variação Genética , Pergelissolo/microbiologia , Lagoas/microbiologia , Bactérias/crescimento & desenvolvimento , Bactérias/isolamento & purificação , Contagem de Colônia Microbiana , Sedimentos Geológicos/microbiologia , Sequenciamento de Nucleotídeos em Larga Escala , Filogenia , Análise de Componente Principal , América do Sul , Água
8.
Bull Exp Biol Med ; 169(1): 67-70, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32488774

RESUMO

We studied the effect of a single intraperitoneal injection of metabolites from Bacillus sp. M3 strain isolated from permafrost (from 5×103 to 50×103 microbial bodies) on differentiation of T cells in the thymus of F1(CBA/Black-6) mice. On day 21 after the injection of metabolites, a dose-dependent decrease in the level of CD34+CD44+ and an increase in the number of CD34+CD44-, CD25-TCR+, CD25+TCR+max, CD4+CD8-, CD4-CD8+, and CD44+TCR+ lymphocytes were observed in the thymus. The increase in thymus level of mature (CD25+TCR+max) and migration-ready (CD44+TCR+) T cells in combination with a moderate decrease in the level of T cell precursors entering the thymus from the bone marrow (CD34+CD44+) can indicate a modulating influence of Bacillus sp. metabolites on functional activity of the thymus aimed at maintenance of the T cell balance in the body.


Assuntos
Bacillus , Extratos Celulares/farmacologia , Pergelissolo/microbiologia , Linfócitos T/efeitos dos fármacos , Animais , Bacillus/química , Bacillus/isolamento & purificação , Bacillus/metabolismo , Diferenciação Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Hematopoese/efeitos dos fármacos , Masculino , Metaboloma/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Linfócitos T/fisiologia , Timo/citologia , Timo/efeitos dos fármacos , Timo/imunologia
9.
Environ Microbiol ; 22(8): 3463-3477, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32510727

RESUMO

A perennially frozen lake at Boulder Clay site (Victoria Land, Antarctica), characterized by the presence of frost mounds, have been selected as an in situ model for ecological studies. Different samples of permafrost, glacier ice and brines have been studied as a unique habitat system. An additional sample of brines (collected in another frozen lake close to the previous one) was also considered. Alpha- and beta-diversity of fungal communities showed both intra- and inter-cores significant (p < 0.05) differences, which suggest the presence of interconnection among the habitats. Therefore, the layers of frost mound and the deep glacier could be interconnected while the brines could probably be considered as an open habitat system not interconnected with each other. Moreover, the absence of similarity between the lake ice and the underlying permafrost suggested that the lake is perennially frozen based. The predominance of positive significant (p < 0.05) co-occurrences among some fungal taxa allowed to postulate the existence of an ecological equilibrium in the habitats systems. The positive significant (p < 0.05) correlation between salt concentration, total organic carbon and pH, and some fungal taxa suggests that a few abiotic parameters could drive fungal diversity inside these ecological niches.


Assuntos
Fungos/classificação , Camada de Gelo/microbiologia , Pergelissolo/microbiologia , Regiões Antárticas , Argila , Ecossistema , Fungos/genética , Camada de Gelo/química , Lagos/química , Lagos/microbiologia , Micobioma , Compostos Orgânicos/análise , Pergelissolo/química , Salinidade , Sais/análise
10.
Microb Genom ; 6(5)2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32392124

RESUMO

The Arctic is warming - fast. Microbes in the Arctic play pivotal roles in feedbacks that magnify the impacts of Arctic change. Understanding the genome evolution, diversity and dynamics of Arctic microbes can provide insights relevant for both fundamental microbiology and interdisciplinary Arctic science. Within this synthesis, we highlight four key areas where genomic insights to the microbial dimensions of Arctic change are urgently required: the changing Arctic Ocean, greenhouse gas release from the thawing permafrost, 'biological darkening' of glacial surfaces, and human activities within the Arctic. Furthermore, we identify four principal challenges that provide opportunities for timely innovation in Arctic microbial genomics. These range from insufficient genomic data to develop unifying concepts or model organisms for Arctic microbiology to challenges in gaining authentic insights to the structure and function of low-biomass microbiota and integration of data on the causes and consequences of microbial feedbacks across scales. We contend that our insights to date on the genomics of Arctic microbes are limited in these key areas, and we identify priorities and new ways of working to help ensure microbial genomics is in the vanguard of the scientific response to the Arctic crisis.


Assuntos
Genômica/métodos , Microbiota , Pergelissolo/microbiologia , Regiões Árticas , Evolução Molecular , Aquecimento Global , Microbiologia do Solo
11.
PLoS One ; 15(4): e0232169, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32353013

RESUMO

Approximately one fourth of the Earth's Northern Hemisphere is underlain by permafrost, earth materials (soil, organic matter, or bedrock), that has been continuously frozen for at least two consecutive years. Numerous studies point to evidence of accelerated climate warming in the Arctic and sub-Arctic where permafrost is located. Changes to permafrost biochemical processes may critically impact ecosystem processes at the landscape scale. Here, we sought to understand how the permafrost metabolome responds to thaw and how this response differs based on location (i.e. chronosequence of permafrost formation constituting diverse permafrost types). We analyzed metabolites from microbial cells originating from Alaskan permafrost. Overall, permafrost thaw induced a shift in microbial metabolic processes. Of note were the dissimilarities in biochemical structure between frozen and thawed samples. The thawed permafrost metabolomes from different locations were highly similar. In the intact permafrost, several metabolites with antagonist properties were identified, illustrating the competitive survival strategy required to survive a frozen state. Interestingly, the intensity of these antagonistic metabolites decreased with warmer temperature, indicating a shift in ecological strategies in thawed permafrost. These findings illustrate the impact of change in temperature and spatial variability as permafrost undergoes thaw, knowledge that will become crucial for predicting permafrost biogeochemical dynamics as the Arctic and Antarctic landscapes continue to warm.


Assuntos
Pergelissolo/química , Pergelissolo/microbiologia , Regiões Antárticas , Regiões Árticas , Ecossistema , Metaboloma/fisiologia , Solo , Microbiologia do Solo , Temperatura
12.
Curr Microbiol ; 77(6): 1061-1069, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32036395

RESUMO

Alpine permafrost regions are important sources of biogenic CH4 and methanogens play an important role in the methane-producing process. The alpine permafrost on the Qinghai-Tibetan plateau comprises about one-sixth of China's land area, and there are various types of alpine ecosystems. However, the methanogenic communities in the typical alpine ecosystems are poorly understood. In this study, the active layers and permafrost layers of the natural ecosystem of alpine grassland (DZ2-1) and alpine swamp meadow (DZ2-5) were selected to investigate the diversity and abundance of methanogenic communities. Methanobacterium (63.65%) are overwhelmingly dominant in the active layer of the alpine grassland (DZ2-1A). ZC-I cluster (26.13%), RC-I cluster (19.56%), and Methanobacterium (15.02%) are the dominant groups in the permafrost layer of the alpine grassland (DZ2-1P). Methanosaeta (32.92%), Fen cluster (29.59%), Methanosarcina (16.33%), and Methanobacterium (13.95%) are the dominant groups in the active layer of the alpine swamp meadow (DZ2-5A), whereas the Fen cluster (50.85%), ZC-I cluster (27.63%), and RC-I cluster (14.15%) are relatively abundant in the permafrost layer of the alpine swamp meadow (DZ2-5P). qPCR data showed that the abundance of methanogens was higher in the natural ecosystem of alpine swamp meadow than in alpine grassland. We found that the community characteristics of methanogens were related to environmental factors. Pearson correlation analyses indicated that the relative abundance of Methanobacterium had a significantly positive correlation with hydrogen concentration (P < 0.01), while the relative abundances of Methanosaeta and Methanosarcina were positively correlated with acetate concentration (P < 0.05). This study will help us to understand the methanogenic communities and their surrounding environments in alpine ecosystems.


Assuntos
Ecossistema , Euryarchaeota/isolamento & purificação , Microbiota , Pergelissolo/microbiologia , Acetatos/análise , Proteínas de Bactérias/genética , Biodiversidade , Euryarchaeota/classificação , Euryarchaeota/genética , Pradaria , Hidrogênio/análise , Microbiota/genética , Pergelissolo/química , Filogenia , Tibet , Áreas Alagadas
13.
Int J Syst Evol Microbiol ; 70(4): 2334-2338, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32022657

RESUMO

A cryophilic basidiomycetous yeast unable to grow at 18 °C or higher temperatures was isolated from a subsurface permafrost layer collected in the Eastern Swiss Alps and from melted sea ice collected in the Artic at Frobisher Bay, Nunavut, Canada. Phylogenetic analyses employing combined sequences of the D1/D2 domain and ITS region indicated that the two new isolates belong to the family Camptobasidiaceae of the class Microbotryomycetes but are distantly related to any of the currently recognized species and genera. Consequently, the novel genus Cryolevonia, and the novel species Cryolevonia schafbergensis (type strain PYCC 8347T=CBS 16055T) are proposed to accommodate this cryophilic yeast. Although sparse hyphae and teliospore-like stuctures were observed upon prolonged incubation, a sexual cycle was not observed and therefore C. schafbergensis is documented solely from its asexual stage.


Assuntos
Basidiomycota/classificação , Camada de Gelo/microbiologia , Pergelissolo/microbiologia , Filogenia , Basidiomycota/isolamento & purificação , Canadá , DNA Fúngico/genética , DNA Espaçador Ribossômico/genética , Técnicas de Tipagem Micológica , Análise de Sequência de DNA , Suíça
14.
Microbiome ; 8(1): 3, 2020 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-31952472

RESUMO

BACKGROUND: It is well-known that global warming has effects on high-latitude tundra underlain with permafrost. This leads to a severe concern that decomposition of soil organic carbon (SOC) previously stored in this region, which accounts for about 50% of the world's SOC storage, will cause positive feedback that accelerates climate warming. We have previously shown that short-term warming (1.5 years) stimulates rapid, microbe-mediated decomposition of tundra soil carbon without affecting the composition of the soil microbial community (based on the depth of 42684 sequence reads of 16S rRNA gene amplicons per 3 g of soil sample). RESULTS: We show that longer-term (5 years) experimental winter warming at the same site altered microbial communities (p < 0.040). Thaw depth correlated the strongest with community assembly and interaction networks, implying that warming-accelerated tundra thaw fundamentally restructured the microbial communities. Both carbon decomposition and methanogenesis genes increased in relative abundance under warming, and their functional structures strongly correlated (R2 > 0.725, p < 0.001) with ecosystem respiration or CH4 flux. CONCLUSIONS: Our results demonstrate that microbial responses associated with carbon cycling could lead to positive feedbacks that accelerate SOC decomposition in tundra regions, which is alarming because SOC loss is unlikely to subside owing to changes in microbial community composition. Video Abstract.


Assuntos
Ciclo do Carbono , Aquecimento Global , Microbiota , Pergelissolo/microbiologia , Microbiologia do Solo , Solo/química , Carbono/metabolismo , Metano/metabolismo , RNA Ribossômico 16S/genética , Estações do Ano
15.
PLoS One ; 15(1): e0226838, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31990908

RESUMO

Lipases comprise a large class of hydrolytic enzymes which catalyze the cleavage of the ester bonds in triacylglycerols and find numerous biotechnological applications. Previously, we have cloned the gene coding for a novel esterase PMGL2 from a Siberian permafrost metagenomic DNA library. We have determined the 3D structure of PMGL2 which belongs to the hormone-sensitive lipase (HSL) family and contains a new variant of the active site motif, GCSAG. Similar to many other HSLs, PMGL2 forms dimers in solution and in the crystal. Our results demonstrated that PMGL2 and structurally characterized members of the GTSAG motif subfamily possess a common dimerization interface that significantly differs from that of members of the GDSAG subfamily of known structure. Moreover, PMGL2 had a unique organization of the active site cavity with significantly different topology compared to the other lipolytic enzymes from the HSL family with known structure including the distinct orientation of the active site entrances within the dimer and about four times larger size of the active site cavity. To study the role of the cysteine residue in GCSAG motif of PMGL2, the catalytic properties and structure of its double C173T/C202S mutant were examined and found to be very similar to the wild type protein. The presence of the bound PEG molecule in the active site of the mutant form allowed for precise mapping of the amino acid residues forming the substrate cavity.


Assuntos
Bactérias/enzimologia , Lipase/química , Lipase/metabolismo , Mutação , Pergelissolo/microbiologia , Motivos de Aminoácidos , Bactérias/química , Bactérias/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Cristalografia por Raios X , Lipase/genética , Metagenoma , Modelos Moleculares , Conformação Proteica , Multimerização Proteica , Serina/metabolismo , Sibéria , Especificidade por Substrato
16.
FEMS Microbiol Ecol ; 96(2)2020 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-31778159

RESUMO

Arctic soils store vast amounts of carbon and are subject to intense climate change. While the effects of thaw on the composition and activities of Arctic tundra microorganisms has been examined extensively, little is known about the consequences of temperature fluctuations within the subzero range in seasonally frozen or permafrost soils. This study identified tundra soil bacteria active at subzero temperatures using stable isotope probing (SIP). Soils from Kilpisjärvi, Finland, were amended with 13C-cellobiose and incubated at 0, -4 and -16°C for up to 40 weeks. 16S rRNA gene sequence analysis of 13C-labelled DNA revealed distinct subzero-active bacterial taxa. The SIP experiments demonstrated that diverse bacteria, including members of Candidatus Saccharibacteria, Melioribacteraceae, Verrucomicrobiaceae, Burkholderiaceae, Acetobacteraceae, Armatimonadaceae and Planctomycetaceae, were capable of synthesising 13C-DNA at subzero temperatures. Differences in subzero temperature optima were observed, for example, with members of Oxalobacteraceae and Rhizobiaceae found to be more active at 0°C than at -4°C or -16°C, whereas Melioribacteriaceae were active at all subzero temperatures tested. Phylogeny of 13C-labelled 16S rRNA genes from the Melioribacteriaceae, Verrucomicrobiaceae and Candidatus Saccharibacteria suggested that these taxa formed subzero-active clusters closely related to members from other cryo-environments. This study demonstrates that subzero temperatures impact active bacterial community composition and activity, which may influence biogeochemical cycles.


Assuntos
Bactérias/isolamento & purificação , Microbiota , Microbiologia do Solo , Tundra , Bactérias/genética , Carbono , Mudança Climática , Finlândia , Pergelissolo/microbiologia , Filogenia , RNA Ribossômico 16S , Temperatura
17.
Environ Int ; 134: 105330, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31759274

RESUMO

Dissolved organic matter (DOM) released from permafrost thaw greatly influences the biogeochemical cycles of, among others, downstream carbon, nitrogen and phosphorus cycles; yet, knowledge of the linkages between bacterial communities with permafrost DOM heterogeneity is limited. Here, we aim at unravelling the responses of bacterial diversities and metabolic profiles to DOM quantity and composition across permafrost thawing gradients by coupling an extensive field investigation with bio-incubation experiments. Richness, evenness and dissimilarities of the whole and rare communities decreased from thermokarst pits to headstreams and to downstream rivers. The assemblages of the abundant subcommunities were mainly determined by ecological drift-driven stochastic processes. Both the optical and the molecular composition of DOM were significantly related to the changes of the whole (rare) bacterial communities (Mantel's correlation > 0.5, p < 0.01). Diversity indices of the whole and rare communities decreased with decreasing relative abundance of tannins, condensed aromatics and more aromatic and oxidized lignins as well as with decreased dissolved organic carbon and intensities of all fluorescence components. Laboratory DOM bio-incubation experiments further confirmed microbial consumption of more aromatic and oxidized compounds as well as decreasing metabolic diversities in terms of microbial degradation and production along permafrost thawing gradients. Our findings suggest that changes in the sources of permafrost-derived DOM induced by global warming can have different influences on the diversity and metabolism of bacterial communities and thus on permafrost carbon climate feedbacks along permafrost thawing gradients.


Assuntos
Bactérias/classificação , Carbono/química , Pergelissolo/microbiologia , Biodiversidade , Aquecimento Global
18.
FEMS Microbiol Ecol ; 95(12)2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31626297

RESUMO

Hypersaline aqueous environments at subzero temperatures are known to be inhabited by microorganisms, yet information on community structure in subzero brines is very limited. Near Utqiagvik, Alaska, we sampled subzero brines (-6°C, 115-140 ppt) from cryopegs, i.e. unfrozen sediments within permafrost that contain relic (late Pleistocene) seawater brine, as well as nearby sea-ice brines to examine microbial community composition and diversity using 16S rRNA gene amplicon sequencing. We also quantified the communities microscopically and assessed environmental parameters as possible determinants of community structure. The cryopeg brines harbored surprisingly dense bacterial communities (up to 108 cells mL-1) and millimolar levels of dissolved and particulate organic matter, extracellular polysaccharides and ammonia. Community composition and diversity differed between the two brine environments by alpha- and beta-diversity indices, with cryopeg brine communities appearing less diverse and dominated by one strain of the genus Marinobacter, also detected in other cold, hypersaline environments, including sea ice. The higher density and trend toward lower diversity in the cryopeg communities suggest that long-term stability and other features of a subzero brine are more important selective forces than in situ temperature or salinity, even when the latter are extreme.


Assuntos
Bactérias/classificação , Camada de Gelo/microbiologia , Pergelissolo/microbiologia , Água do Mar/microbiologia , Alaska , Regiões Árticas , Bactérias/genética , Bactérias/isolamento & purificação , Temperatura Baixa , Microbiota , Filogenia , RNA Ribossômico 16S/genética , Salinidade , Sais , Temperatura
19.
Extremophiles ; 23(6): 747-757, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31489482

RESUMO

16S rRNA gene profiling is a powerful method for characterizing microbial communities; however, no universal primer pair can target all bacteria and archaea, resulting in different primer pairs which may impact the diversity profile obtained. Here, we evaluated three pairs of high-throughput sequencing primers for characterizing archaeal communities from deep-sea sediments and permafrost soils. The results show that primer pair Arch519/Arch915 (V4-V5 regions) produced the highest alpha diversity estimates, followed by Arch349f/Arch806r (V3-V4 regions) and A751f/AU1204r (V5-V7 regions) in both sample types. The archaeal taxonomic compositions and the relative abundance estimates of archaeal communities are influenced by the primer pairs. Beta diversity of the archaeal community detected by the three primer pairs reveals that primer pairs Arch349f/Arch806r and Arch519f/Arch915r are biased toward detection of Halobacteriales, Methanobacteriales and MBG-E/Hydrothermarchaeota, whereas the primer pairs Arch519f/Arch915r and A751f/UA1204r are biased to detect MBG-B/Lokiarchaeota, and the primers pairs Arch349f/Arch806r and A751f/UA1204r are biased to detect Methanomicrobiales and Methanosarcinales. The data suggest that the alpha and beta diversities of archaeal communities as well as the community compositions are influenced by the primer pair choice. This finding provides researchers with valuable experimental insight for selection of appropriate archaeal primer pairs to characterize archaeal communities.


Assuntos
Archaea , Primers do DNA , DNA Arqueal , Sedimentos Geológicos/microbiologia , Pergelissolo/microbiologia , Microbiologia do Solo , Archaea/classificação , Archaea/genética , Primers do DNA/química , Primers do DNA/genética , DNA Arqueal/química , DNA Arqueal/genética
20.
ISME J ; 13(12): 2901-2915, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31384013

RESUMO

The susceptibility of soil organic carbon (SOC) in tundra to microbial decomposition under warmer climate scenarios potentially threatens a massive positive feedback to climate change, but the underlying mechanisms of stable SOC decomposition remain elusive. Herein, Alaskan tundra soils from three depths (a fibric O horizon with litter and course roots, an O horizon with decomposing litter and roots, and a mineral-organic mix, laying just above the permafrost) were incubated. Resulting respiration data were assimilated into a 3-pool model to derive decomposition kinetic parameters for fast, slow, and passive SOC pools. Bacterial, archaeal, and fungal taxa and microbial functional genes were profiled throughout the 3-year incubation. Correlation analyses and a Random Forest approach revealed associations between model parameters and microbial community profiles, taxa, and traits. There were more associations between the microbial community data and the SOC decomposition parameters of slow and passive SOC pools than those of the fast SOC pool. Also, microbial community profiles were better predictors of model parameters in deeper soils, which had higher mineral contents and relatively greater quantities of old SOC than in surface soils. Overall, our analyses revealed the functional potential of microbial communities to decompose tundra SOC through a suite of specialized genes and taxa. These results portray divergent strategies by which microbial communities access SOC pools across varying depths, lending mechanistic insights into the vulnerability of what is considered stable SOC in tundra regions.


Assuntos
Archaea/isolamento & purificação , Bactérias/isolamento & purificação , Carbono/análise , Fungos/isolamento & purificação , Microbiota , Microbiologia do Solo , Archaea/classificação , Archaea/genética , Bactérias/classificação , Bactérias/genética , Carbono/metabolismo , Mudança Climática , Fungos/classificação , Fungos/genética , Pergelissolo/microbiologia , Solo/química , Tundra
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