| 1. |
- Bravo, Andrea Garcia, et al.
(författare)
-
Geobacteraceae are important members of mercury-methylating microbial communities of sediments impacted by waste water releases
- 2018
-
Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 12, s. 802-812
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Tidskriftsartikel (refereegranskat)abstract
- Microbial mercury (Hg) methylation in sediments can result in bioaccumulation of the neurotoxin methylmercury (MMHg) in aquatic food webs. Recently, the discovery of the gene hgcA, required for Hg methylation, revealed that the diversity of Hg methylators is much broader than previously thought. However, little is known about the identity of Hg-methylating microbial organisms and the environmental factors controlling their activity and distribution in lakes. Here, we combined high-throughput sequencing of 16S rRNA and hgcA genes with the chemical characterization of sediments impacted by a waste water treatment plant that releases significant amounts of organic matter and iron. Our results highlight that the ferruginous geochemical conditions prevailing at 1–2 cm depth are conducive to MMHg formation and that the Hgmethylating guild is composed of iron and sulfur-transforming bacteria, syntrophs, and methanogens. Deltaproteobacteria, notably Geobacteraceae, dominated the hgcA carrying communities, while sulfate reducers constituted only a minor component, despite being considered the main Hg methylators in many anoxic aquatic environments. Because iron is widely applied in waste water treatment, the importance of Geobacteraceae for Hg methylation and the complexity of Hgmethylating communities reported here are likely to occur worldwide in sediments impacted by waste water treatment plant discharges and in iron-rich sediments in general.
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| 2. |
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| 3. |
- Bravo, Andrea G., et al.
(författare)
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Methanogens and iron-reducing bacteria : the overlooked members of mercury-methylating microbial communities in boreal lakes
- 2018
-
Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 84:23
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Methylmercury is a potent human neurotoxin which biomagnifies in aquatic food webs. Although anaerobic microorganisms containing the hgcA gene potentially mediate the formation of methylmercury in natural environments, the diversity of these mercury-methylating microbial communities remains largely unexplored. Previous studies have implicated sulfate-reducing bacteria as the main mercury methylators in aquatic ecosystems. In the present study, we characterized the diversity of mercury-methylating microbial communities of boreal lake sediments using high-throughput sequencing of 16S rRNA and hgcA genes. Our results show that in the lake sediments, Methanomicrobiales and Geobacteraceae also represent abundant members of the mercury-methylating communities. In fact, incubation experiments with a mercury isotopic tracer and molybdate revealed that only between 38% and 45% of mercury methylation was attributed to sulfate reduction. These results suggest that methanogens and iron-reducing bacteria may contribute to more than half of the mercury methylation in boreal lakes.IMPORTANCE: Despite the global awareness that mercury, and methylmercury in particular, is a neurotoxin to which millions of people continue to be exposed, there are sizable gaps in the understanding of the processes and organisms involved in methylmercury formation in aquatic ecosystems. In the present study, we shed light on the diversity of the microorganisms responsible for methylmercury formation in boreal lake sediments. All the microorganisms identified are associated with the processing of organic matter in aquatic systems. Moreover, our results show that the well-known mercury-methylating sulfate-reducing bacteria constituted only a minor portion of the potential mercury methylators. In contrast, methanogens and iron-reducing bacteria were important contributors to methylmercury formation, highlighting their role in mercury cycling in the environment.
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| 4. |
- Bravo, Andrea Garcia, et al.
(författare)
-
Methanogens and Iron-Reducing Bacteria : the Overlooked Members of Mercury-Methylating Microbial Communities in Boreal Lakes
- 2018
-
Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 84:23
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury is a potent human neurotoxin which biomagnifies in aquatic food webs. Although anaerobic microorganisms containing the hgcA gene potentially mediate the formation of methylmercury in natural environments, the di- versity of these mercury-methylating microbial communities remains largely unex- plored. Previous studies have implicated sulfate-reducing bacteria as the main mer- cury methylators in aquatic ecosystems. In the present study, we characterized the diversity of mercury-methylating microbial communities of boreal lake sediments us- ing high-throughput sequencing of 16S rRNA and hgcA genes. Our results show that in the lake sediments, Methanomicrobiales and Geobacteraceae also represent abun- dant members of the mercury-methylating communities. In fact, incubation experi- ments with a mercury isotopic tracer and molybdate revealed that only between 38% and 45% of mercury methylation was attributed to sulfate reduction. These re- sults suggest that methanogens and iron-reducing bacteria may contribute to more than half of the mercury methylation in boreal lakes.
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| 5. |
- Buck, Moritz, et al.
(författare)
-
16S rRNA gene sequences of Candidatus Methylumidiphilus (Methylococcales), a putative methanotrophic genus in lakes and ponds
- 2022
-
Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 88, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- A putative novel methanotrophic genus, Candidatus Methylumidiphilus (Methylococcales), was recently shown to be ubiquitous and one of the most abundant methanotrophic genera in water columns of oxygen-stratified lakes and ponds in boreal and subarctic areas. However, it has probably escaped detection in many previous studies that used 16S rRNA gene amplicon sequencing due to insufficient database coverage, as previously analysed metagenome-assembled genomes (MAGs) affiliated with Ca. Methylumidiphilus do not contain 16S rRNA genes. Therefore, we screened MAGs affiliated with the genus for their 16S rRNA gene sequences in a recently published lake and pond MAG data set. Among 66 MAGs classified as Ca. Methylumidiphilus (with completeness over 40% and contamination less than 5 %) originating from lakes in Finland, Sweden and Switzerland as well as from ponds in Canada, we found 5 MAGs, each containing one 1532 bp sequence spanning the V1-V9 regions of the 16S rRNA gene. After removal of sequence redundancy, this resulted in 2 unique 16S rRNA gene sequences. These sequences represented 2 different putative species: Ca. Methylumidiphilus alinenensis (GenBank accession OK236221) and another unnamed species of Ca. Methylumidiphilus (GenBank accession OK236220). We suggest that including these 2 sequences in reference databases will enhance 16S rRNA gene-based detection of members of this genus from environmental samples.
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| 6. |
- Buck, Moritz, et al.
(författare)
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Comprehensive dataset of shotgun metagenomes from oxygen stratified freshwater lakes and ponds
- 2021
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Stratified lakes and ponds featuring steep oxygen gradients are significant net sources of greenhouse gases and hotspots in the carbon cycle. Despite their significant biogeochemical roles, the microbial communities, especially in the oxygen depleted compartments, are poorly known. Here, we present a comprehensive dataset including 267 shotgun metagenomes from 41 stratified lakes and ponds mainly located in the boreal and subarctic regions, but also including one tropical reservoir and one temperate lake. For most lakes and ponds, the data includes a vertical sample set spanning from the oxic surface to the anoxic bottom layer. The majority of the samples were collected during the open water period, but also a total of 29 samples were collected from under the ice. In addition to the metagenomic sequences, the dataset includes environmental variables for the samples, such as oxygen, nutrient and organic carbon concentrations. The dataset is ideal for further exploring the microbial taxonomic and functional diversity in freshwater environments and potential climate change impacts on the functioning of these ecosystems.
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| 7. |
- Buck, Moritz, et al.
(författare)
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mOTUpan: a robust Bayesian approach to leverage metagenome-assembled genomes for core-genome estimation
- 2022
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Ingår i: NAR genomics and bioinformatics. - : Oxford University Press (OUP). - 2631-9268. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in sequencing and bioinformatics have expanded the tree of life by providing genomes for uncultured environmentally relevant clades, either through metagenome-assembled genomes or through single-cell genomes. While this expanded diversity can provide novel insights into microbial population structure, most tools available for core-genome estimation are sensitive to genome completeness. Consequently, a major portion of the huge phylogenetic diversity uncovered by environmental genomic approaches remains excluded from such analyses. We present mOTUpan, a novel iterative Bayesian method for computing the core genome for sets of genomes of highly diverse completeness range. The likelihood for each gene cluster to belong to core or accessory genome is estimated by computing the probability of its presence/absence pattern in the target genome set. The core-genome prediction is computationally efficient and can be scaled up to thousands of genomes. It has shown comparable estimates to state-of-the-art tools Roary and PPanGGOLiN for high-quality genomes and is capable of using genomes at lower completeness thresholds. mOTUpan wraps a bootstrapping procedure to estimate the quality of a specific core-genome prediction, as the accuracy of each run will depend on the specific completeness distribution and the number of genomes in the dataset under scrutiny. mOTUpan is implemented in the mOTUlizer software package, and available at github.com/moritzbuck/mOTUlizer, under GPL 3.0 license.
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| 8. |
- Capo, Eric, et al.
(författare)
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A consensus protocol for the recovery of mercury methylation genes from metagenomes
- 2023
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Ingår i: Molecular Ecology Resources. - : John Wiley & Sons. - 1755-098X .- 1755-0998. ; 23:1, s. 190-204
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) methylation genes (hgcAB) mediate the formation of the toxic methylmercury and have been identified from diverse environments, including freshwater and marine ecosystems, Arctic permafrost, forest and paddy soils, coal-ash amended sediments, chlor-alkali plants discharges and geothermal springs. Here we present the first attempt at a standardized protocol for the detection, identification and quantification of hgc genes from metagenomes. Our Hg-cycling microorganisms in aquatic and terrestrial ecosystems (Hg-MATE) database, a catalogue of hgc genes, provides the most accurate information to date on the taxonomic identity and functional/metabolic attributes of microorganisms responsible for Hg methylation in the environment. Furthermore, we introduce "marky-coco", a ready-to-use bioinformatic pipeline based on de novo single-metagenome assembly, for easy and accurate characterization of hgc genes from environmental samples. We compared the recovery of hgc genes from environmental metagenomes using the marky-coco pipeline with an approach based on coassembly of multiple metagenomes. Our data show similar efficiency in both approaches for most environments except those with high diversity (i.e., paddy soils) for which a coassembly approach was preferred. Finally, we discuss the definition of true hgc genes and methods to normalize hgc gene counts from metagenomes.
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| 9. |
- Capo, Eric, et al.
(författare)
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Deltaproteobacteria andSpirochaetes-Like Bacteria AreAbundant Putative MercuryMethylators in Oxygen-DeficientWater and Marine Particles in theBaltic Sea
- 2020
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; , s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury (MeHg), a neurotoxic compound biomagnifying in aquatic food webs, can be a threat to human health via fish consumption. However, the compositionand distribution of the microbial communities mediating the methylation of mercury (Hg) to MeHg in marine systems remain largely unknown. In order to fill this knowledge gap, we used the Baltic Sea Reference Metagenome (BARM) dataset to study the abundance and distribution of the genes involved in Hg methylation (the hgcAB gene cluster). We determined the relative abundance of the hgcAB genes and their taxonomic identity in 81 brackish metagenomes that cover spatial,seasonal and redox variability in the Baltic Sea water column. The hgcAB genes were predominantly detected in anoxic water, but some hgcAB genes were alsodetected in hypoxic and normoxic waters. Phylogenetic analysis identified putative Hg methylators within Deltaproteobacteria, in oxygen-deficient water layers, but also Spirochaetes-like and Kiritimatiellaeota-like bacteria. Higher relative quantities of hgcAB genes were found in metagenomes from marine particles compared to free-living communities in anoxic water, suggesting that such particles are hotspot habitats for Hg methylators in oxygen-depleted seawater. Altogether, our work unveils the diversityof the microorganisms with the potential to mediate MeHg production in the BalticSea and pinpoint the important ecological niches for these microorganisms within themarine water column.
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| 10. |
- Capo, Eric, et al.
(författare)
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Expression Levels of hgcAB Genes and Mercury Availability Jointly Explain Methylmercury Formation in Stratified Brackish Waters
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:18, s. 13119-13130
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Tidskriftsartikel (refereegranskat)abstract
- Neurotoxic methylmercury (MeHg) is formed by microbial methylation of inorganic divalent Hg (Hg-II) and constitutes severe environmental and human health risks. The methylation is enabled by hgcA and hgcB genes, but it is not know nif the associated molecular-level processes are rate-limiting or enable accurate prediction of MeHg formation in nature. In this study, we investigated the relationships between hgc genes and MeHg across redox-stratified water columns in the brackish Baltic Sea. We showed, for the first time, that hgc transcript abundance and the concentration of dissolved Hg-II-sulfide species were strong predictors of both the Hg-II methylation rate and MeHg concentration, implying their roles as principal joint drivers of MeHg formation in these systems. Additionally, we characterized the metabolic capacities of hgc(+) microorganisms by reconstructing their genomes from metagenomes (i.e., hgc(+) MAGs), which highlighted the versatility of putative Hg-II methylators in the water column of the Baltic Sea. In establishing relationships between hgc transcripts and the Hg-II methylation rate, we advance the fundamental understanding of mechanistic principles governing MeHg formation in nature and enable refined predictions of MeHg levels in coastal seas in response to the accelerating spread of oxygen-deficientzones.
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| 11. |
- Capo, Eric, et al.
(författare)
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Oxygen-deficient water zones in the Baltic Sea promote uncharacterized Hg methylating microorganisms in underlying sediments
- 2022
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Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 67:1, s. 135-146
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Tidskriftsartikel (refereegranskat)abstract
- Human-induced expansion of oxygen-deficient zones can have dramatic impacts on marine systems and its resident biota. One example is the formation of the potent neurotoxic methylmercury (MeHg) that is mediated by microbial methylation of inorganic divalent Hg (HgII) under oxygen-deficient conditions. A negative consequence of the expansion of oxygen-deficient zones could be an increase in MeHg production due to shifts in microbial communities in favor of microorganisms methylating Hg. There is, however, limited knowledge about Hg-methylating microbes, i.e., those carrying hgc genes critical for mediating the process, from marine sediments. Here, we aim to study the presence of hgc genes and transcripts in metagenomes and metatranscriptomes from four surface sediments with contrasting concentrations of oxygen and sulfide in the Baltic Sea. We show that potential Hg methylators differed among sediments depending on redox conditions. Sediments with an oxygenated surface featured hgc-like genes and transcripts predominantly associated with uncultured Desulfobacterota (OalgD group) and Desulfobacterales (including Desulfobacula sp.) while sediments with a hypoxic-anoxic surface included hgc-carrying Verrucomicrobia, unclassified Desulfobacterales, Desulfatiglandales, and uncharacterized microbes. Our data suggest that the expansion of oxygen-deficient zones in marine systems may lead to a compositional change of Hg-methylating microbial groups in the sediments, where Hg methylators whose metabolism and biology have not yet been characterized will be promoted and expand.
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| 12. |
- Christel, Stephan, et al.
(författare)
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RNA transcript sequencing reveals inorganic sulfur compound oxidation pathways in the acidophile Acidithiobacillus ferrivorans
- 2016
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 363:7
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Tidskriftsartikel (refereegranskat)abstract
- Acidithiobacillus ferrivorans is an acidophile implicated in low-temperature biomining for the recovery of metals from sulfide minerals. Acidithiobacillus ferrivorans obtains its energy from the oxidation of inorganic sulfur compounds, and genes encoding several alternative pathways have been identified. Next-generation sequencing of At. ferrivorans RNA transcripts identified the genes coding for metabolic and electron transport proteins for energy conservation from tetrathionate as electron donor. RNA transcripts suggested that tetrathionate was hydrolyzed by the tetH1 gene product to form thiosulfate, elemental sulfur and sulfate. Despite two of the genes being truncated, RNA transcripts for the SoxXYZAB complex had higher levels than for thiosulfate quinone oxidoreductase (doxDA genes). However, a lack of heme-binding sites in soxX suggested that DoxDA was responsible for thiosulfate metabolism. Higher RNA transcript counts also suggested that elemental sulfur was metabolized by heterodisulfide reductase (hdr genes) rather than sulfur oxygenase reductase (sor). The sulfite produced as a product of heterodisulfide reductase was suggested to be oxidized by a pathway involving the sat gene product or abiotically react with elemental sulfur to form thiosulfate. Finally, several electron transport complexes were involved in energy conservation. This study has elucidated the previously unknown At. ferrivorans tetrathionate metabolic pathway that is important in biomining.
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| 13. |
- Corcoll, Natàlia, 1981, et al.
(författare)
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Comparison of different DNA extraction methods for marine periphyton and its implications for ecotoxico-metagenomics
- 2015
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Ingår i: Poster Presentation at the SETAC Europe 25th Annual Meeting, Barcelona, Spain.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This is a time with unprecedented capacity of DNA sequencing technologies for metagenomic analysis (identifying new genes and species living in environmental samples) in natural communities. However, sequencing efforts on non-model organisms or communities, such as marine periphyton communities, are still scarce in ecotoxicology. Also, uncertainties in basic aspects, such as choice of appropriate DNA extraction method, are still not resolved. This study aims to compare the effects of different DNA extraction methods for marine periphyton in terms of DNA yield, purity and integrity, as well as eukaryotic and prokaryotic diversity. Cost-effectiveness among the methods was also assessed. Four different methods (the Plant DNAzol reagent (Invitrogen), the Fast DNA Spin kit for soil (MP Biomedicals), the PowerPlant and the PowerBiofilm DNA Isolation Kits (MoBio Laboratories)) commonly used for DNA extraction of eukaryotic and prokaryotic microorganisms from marine periphyton were compared. Results showed that the commercial method Plant DNAzol reagent and the Fast DNA Spin kit for soil appear to be the best to extract high quantities of DNA (> 50 ng/μL). DNA fragments obtained with these methods cover a wide range of sizes, from 250 to 15000 bp. With the PowerPlant and the PowerBiofilm DNA Isolation Kits, lower amounts of DNA were obtained (< 23 ng/μL), but the purity of these extractions, in terms of protein and polysaccharide contamination, was higher. Extractions from these latter kits also produced DNA size distributions with larger sizes, between 3000 and 15000 bp. Obtained DNA products were used for amplicon sequencing of the 18S rRNA and 16S rRNA genes, targeting eukaryotes and prokaryotes, respectively. Such DNA amplicon sequencing will be a powerful tool to compare community composition and biodiversity across samples, and to select DNA extraction method for further metagenomics of periphyton communities exposed to toxicants.
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| 14. |
- Donis, Daphne, et al.
(författare)
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Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer
- 2021
-
Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:12, s. 4314-4333
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Tidskriftsartikel (refereegranskat)abstract
- To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature.
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| 15. |
- Eklöf, Karin, et al.
(författare)
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Formation of mercury methylation hotspots as a consequence of forestry operations
- 2018
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 613-614, s. 1069-1078
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Tidskriftsartikel (refereegranskat)abstract
- Earlier studies have shown that boreal forest logging can increase the concentration and export of methylmercury (MeHg) in stream runoff. Here we test whether forestry operations create soil environments of high MeHg net formation associated with distinct microbial communities. Furthermore, we test the hypothesis that Hg methylation hotspots are more prone to form after stump harvest than stem-only harvest, because of more severe soil compaction and soil disturbance. Concentrations of MeHg, percent MeHg of total Hg (THg), and bacterial community composition were determined at 200 soil sampling positions distributed across eight catchments. Each catchment was either stem-only harvested (n = 3), stem-and stump-harvested (n = 2) or left undisturbed (n = 3). In support of our hypothesis, higher MeHg to THg ratios was observed in one of the stump-harvested catchments. While the effects of natural variation could not be ruled out, we noted that most of the highest % MeHg was observed in water-filled cavities created by stump removal or driving damage. This catchment also featured the highest bacterial diversity and highest relative abundance of bacterial families known to include Hg methylators. We propose that water-logged and disturbed soil environments associated with stump harvest can favor methylating microorganisms, which also enhance MeHg formation.
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| 16. |
- Garcia, Sarahi L., et al.
(författare)
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Auxotrophy and intrapopulation complementary in the "interactome' of a cultivated freshwater model community
- 2015
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 24:17, s. 4449-4459
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Tidskriftsartikel (refereegranskat)abstract
- Microorganisms are usually studied either in highly complex natural communities or in isolation as monoclonal model populations that we manage to grow in the laboratory. Here, we uncover the biology of some of the most common and yet-uncultured bacteria in freshwater environments using a mixed culture from Lake Grosse Fuchskuhle. From a single shotgun metagenome of a freshwater mixed culture of low complexity, we recovered four high-quality metagenome-assembled genomes (MAGs) for metabolic reconstruction. This analysis revealed the metabolic interconnectedness and niche partitioning of these naturally dominant bacteria. In particular, vitamin- and amino acid biosynthetic pathways were distributed unequally with a member of Crenarchaeota most likely being the sole producer of vitamin B12 in the mixed culture. Using coverage-based partitioning of the genes recovered from a single MAG intrapopulation metabolic complementarity was revealed pointing to social' interactions for the common good of populations dominating freshwater plankton. As such, our MAGs highlight the power of mixed cultures to extract naturally occurring interactomes' and to overcome our inability to isolate and grow the microbes dominating in nature.
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| 17. |
- Garcia, Sarahi L., et al.
(författare)
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Freshwater Chlorobia Exhibit Metabolic Specialization among Cosmopolitan and Endemic Populations
- 2021
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Ingår i: mSystems. - : American Society for Microbiology. - 2379-5077. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic bacteria from the class Chlorobia (formerly phylum Chlorobi) sustain carbon fixation in anoxic water columns. They harvest light at extremely low intensities and use various inorganic electron donors to fix carbon dioxide into biomass. Until now, most information on the functional ecology and local adaptations of Chlorobia members came from isolates and merely 26 sequenced genomes that may not adequately represent natural populations. To address these limitations, we analyzed global metagenomes to profile planktonic Chlorobia cells from the oxyclines of 42 freshwater bodies, spanning subarctic to tropical regions and encompassing all four seasons. We assembled and compiled over 500 genomes, including metagenome-assembled genomes (MAGs), single-amplified genomes (SAGs), and reference genomes from cultures, clustering them into 71 metagenomic operational taxonomic units (mOTUs or “species”). Of the 71 mOTUs, 57 were classified within the genus Chlorobium, and these mOTUs represented up to ∼60% of the microbial communities in the sampled anoxic waters. Several Chlorobium-associated mOTUs were globally distributed, whereas others were endemic to individual lakes. Although most clades encoded the ability to oxidize hydrogen, many lacked genes for the oxidation of specific sulfur and iron substrates. Surprisingly, one globally distributed Scandinavian clade encoded the ability to oxidize hydrogen, sulfur, and iron, suggesting that metabolic versatility facilitated such widespread colonization. Overall, these findings provide new insight into the biogeography of the Chlorobia and the metabolic traits that facilitate niche specialization within lake ecosystems.
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| 18. |
- Garcia, Sarahi L, et al.
(författare)
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Model Communities Hint at Promiscuous Metabolic Linkages between Ubiquitous Free-Living Freshwater Bacteria
- 2018
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Ingår i: mSphere. - : AMER SOC MICROBIOLOGY. - 2379-5042. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Genome streamlining is frequently observed in free-living aquatic microorganisms and results in physiological dependencies between microorganisms. However, we know little about the specificity of these microbial associations. In order to examine the specificity and extent of these associations, we established mixed cultures from three different freshwater environments and analyzed the cooccurrence of organisms using a metagenomic time series. Free-living microorganisms with streamlined genomes lacking multiple biosynthetic pathways showed no clear recurring pattern in their interaction partners. Free-living freshwater bacteria form promiscuous cooperative associations. This notion contrasts with the well-documented high specificities of interaction partners in host-associated bacteria. Considering all data together, we suggest that highly abundant free-living bacterial lineages are functionally versatile in their interactions despite their distinct streamlining tendencies at the single-cell level. This metabolic versatility facilitates interactions with a variable set of community members.
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| 19. |
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| 20. |
- Hubalek, Valerie, et al.
(författare)
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Connectivity to the surface determines diversity patterns in subsurface aquifers of the Fennoscandian shield
- 2016
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 10:10, s. 2447-2458
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Tidskriftsartikel (refereegranskat)abstract
- Little research has been conducted on microbial diversity deep under the Earth/'s surface. In this study, the microbial communities of three deep terrestrial subsurface aquifers were investigated. Temporal community data over 6 years revealed that the phylogenetic structure and community dynamics were highly dependent on the degree of isolation from the earth surface biomes. The microbial community at the shallow site was the most dynamic and was dominated by the sulfur-oxidizing genera Sulfurovum or Sulfurimonas at all-time points. The microbial community in the meteoric water filled intermediate aquifer (water turnover approximately every 5 years) was less variable and was dominated by candidate phylum OD1. Metagenomic analysis of this water demonstrated the occurrence of key genes for nitrogen and carbon fixation, sulfate reduction, sulfide oxidation and fermentation. The deepest water mass (5000 year old waters) had the lowest taxon richness and surprisingly contained Cyanobacteria. The high relative abundance of phylogenetic groups associated with nitrogen and sulfur cycling, as well as fermentation implied that these processes were important in these systems. We conclude that the microbial community patterns appear to be shaped by the availability of energy and nutrient sources via connectivity to the surface or from deep geological processes.
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| 21. |
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| 22. |
- Hubalek, Valerie, 1981-, et al.
(författare)
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Vitamin and Amino Acid Auxotrophy in Anaerobic Consortia Operating under Methanogenic Conditions
- 2017
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Ingår i: mSystems. - 2379-5077. ; 2:5
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Tidskriftsartikel (refereegranskat)abstract
- Syntrophy among Archaea and Bacteria facilitates the anaerobic degra- dation of organic compounds to CH4 and CO2 . Particularly during aliphatic and aro- matic hydrocarbon mineralization, as in the case of crude oil reservoirs and petroleum-contaminated sediments, metabolic interactions between obligate mutu- alistic microbial partners are of central importance. Using micromanipulation com- bined with shotgun metagenomic approaches, we describe the genomes of complex consortia within short-chain alkane-degrading cultures operating under methano- genic conditions. Metabolic reconstruction revealed that only a small fraction of genes in the metagenome-assembled genomes encode the capacity for fermenta- tion of alkanes facilitated by energy conservation linked to H2 metabolism. Instead, the presence of inferred lifestyles based on scavenging anabolic products and inter- mediate fermentation products derived from detrital biomass was a common fea- ture. Additionally, inferred auxotrophy for vitamins and amino acids suggests that the hydrocarbon-degrading microbial assemblages are structured and maintained by multiple interactions beyond the canonical H2 -producing and syntrophic alkane degrader-methanogen partnership. Compared to previous work, our report points to a higher order of complexity in microbial consortia engaged in anaerobic hydrocar- bon transformation. IMPORTANCE
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| 23. |
- Hötzinger, Matthias, et al.
(författare)
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Geographic population structure and distinct intra-population dynamics of globally abundant freshwater bacteria
- 2024
-
Ingår i: ISME Journal. - 1751-7362 .- 1751-7370. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Implications of geographic separation and temporal dynamics on the evolution of free-living bacterial species are widely unclear. However, the vast amount of metagenome sequencing data generated during the last decades from various habitats around the world provides an unprecedented opportunity for such investigations. Here, we exploited publicly available and new freshwater metagenomes in combination with the genomes of abundant freshwater bacteria to reveal geographic and temporal population structure. We focused on species that were detected across broad geographic ranges at high enough sequence coverage for meaningful population genomic analyses, associated with the predominant freshwater taxa acI, LD12, Polynucleobacter, and Candidatus Methylopumilus. Despite the broad geographic ranges, each species appeared as a sequence-discrete cluster, in contrast to abundant marine taxa, for which continuous diversity structures were reported on a global scale. Population differentiation increased significantly with spatial distance in all species, but notable dispersal barriers (e.g. oceanic) were not apparent. Yet, the different species showed contrasting rates of geographic divergence and strikingly different intra-population dynamics in time series within individual habitats. The change in an LD12 population over 7 years was minor (FST = 0.04) compared to differentiation between lakes, whereas a Polynucleobacter population displayed strong changes within merely 2 months (FST up to 0.54), similar in scale to differentiation between populations separated by thousands of kilometers. The slowly and steadily evolving LD12 population showed high strain diversity, whereas the dynamic Polynucleobacter population exhibited alternating clonal expansions of mostly two strains only. Based on the contrasting population structures, we propose distinct models of speciation.
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| 24. |
- Jingying, Xu, 1984-, et al.
(författare)
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Mercury methylating microbial communities in boreal wetlands
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the formation of the potent neurotoxic methylmercury (MeHg) is a major concern due to its threats to wildlife and human health. As boreal wetlands play a crucial role for Hg cycling on a global scale, it is crucial to understand the biogeochemical processes involved in MeHg formation in this landscape. A strategy combining high-throughput hgcA amplicon sequencing with molecular barcoding was used to revealed diverse clades of Hg(II) methylators in a wide range of wetland soils. Our results confirms a predominant role of Deltaproteobacteria, and in particular Geobacteraceae, as important Hg(II) methylators in boreal wetland soils. Firmicutes, and in particular Ruminococcaceae, were also abundant members of the Hg(II) methylating microbial communities. Our survey highlight the importance of nutrient status for the shaping of Hg(II) methylating communities across the four wetlands and reveal that water content and prevailing redox states are key factors determining the local variation in Hg(II) methylating community composition within individual wetlands. Also, our study suggests that high nutrient levels linked to low redox potential seemed to favour Hg(II) methylating methanogens within the Methanoregulaceae. Our findings expand the current knowledge on the Hg(II) methylating microbial community composition in wetland soils and the geochemical factors underpinning spatial heterogeity in such communities.
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| 25. |
- Jingying, Xu, 1984-, et al.
(författare)
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Mercury methylating microbial communities of boreal forest soils
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is linked to the composition of also non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.
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