| 1. |
- Annenkova, Nataliia V., et al.
(författare)
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Delineating closely related dinoflagellate lineages using phylotranscriptomics
- 2018
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 54:4, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- Recently radiated dinoflagellates Apocalathium aciculiferum (collected in Lake Erken, Sweden), Apocalathium malmogiense (Baltic Sea) and Apocalathium aff. malmogiense (Highway Lake, Antarctica) represent a lineage with an unresolved phylogeny. We determined their phylogenetic relationships using phylotranscriptomics based on 792 amino acid sequences. Our results showed that A. aciculiferum diverged from the other two closely related lineages, consistent with their different morphologies in cell size, relative cell length and presence of spines. We hypothesized that A. aff. malmogiense and A. malmogiense, which inhabit different hemispheres, are evolutionarily more closely related because they diverged from a marine common ancestor, adapting to a wide salinity range, while A. aciculiferum colonized a freshwater habitat, by acquiring adaptations to this environment, in particular, salinity intolerance. We show that phylotranscriptomics can resolve the phylogeny of recently diverged protists. This has broad relevance, given that many phytoplankton species are morphologically very similar, and single genes sometimes lack the information to determine species’ relationships.
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| 2. |
- Bråte, Jon, et al.
(författare)
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Freshwater Perkinsea and marine-freshwater colonizations revealed by pyrosequencing and phylogeny of environmental rDNA
- 2010
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Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 4:9, s. 1144-1153
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Tidskriftsartikel (refereegranskat)abstract
- Protist parasites are ecologically important, as they can have great impact on host population dynamics and functioning of entire ecosystems. Nevertheless, little is known about their prevalence in aquatic habitats. Here, we investigate the diversity and distributional patterns of the protist parasites Perkinsus and Parvilucifera (Perkinsea). Our approach included 454 pyrosequencing of the 18S rDNA gene obtained from a high-altitude lake (Lake Finsevatn, Norway) and phylogenetic analyses of all publicly available sequences related to Perkinsea. The applied PCR primers target a 450 bp region that encompass the variable V4 region of the 18S rDNA gene and have been optimized for the Titanium upgrade of the 454 technology. Nearly 5000 sequences longer than 150 bp were recovered from nearly all eukaryotic supergroups, and of those, 13 unique sequences were affiliated to Perkinsea. Thus, our new strategy for 454 amplicon sequencing was able to recover a large diversity of distantly related eukaryotes and previously unknown species of Perkinsea. In addition, we identified 40 Perkinsea sequences in GenBank generated by other recent diversity surveys. Importantly, phylogenetic analyses of these sequences identified 17 habitat-specific marine and freshwater clades (PERK 1-17). Hence, only a few successful transitions between these habitats have taken place over the entire history of Perkinsea, suggesting that the boundary between marine and fresh waters may constitute a barrier to cross-colonizations for intracellular parasites.
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| 3. |
- Dinasquet, Julie, et al.
(författare)
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Mixing of water masses caused by a drifting iceberg affects bacterial activity, community composition and substrate utilization capability in the Southern Ocean
- 2017
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Ingår i: Environmental Microbiology. - : Wiley-Blackwell. - 1462-2912 .- 1462-2920. ; 19:6, s. 2453-2467
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Tidskriftsartikel (refereegranskat)abstract
- The number of icebergs produced from ice-shelf disintegration has increased over the past decade in Antarctica. These drifting icebergs mix the water column, influence stratification and nutrient condition, and can affect local productivity and food web composition. Data on whether icebergs affect bacterioplankton function and composition are scarce, however. We assessed the influence of iceberg drift on bacterial community composition and on their ability to exploit carbon substrates during summer in the coastal Southern Ocean. An elevated bacterial production and a different community composition were observed in iceberg-influenced waters relative to the undisturbed water column nearby. These major differences were confirmed in short-term incubations with bromodeoxyuridine followed by CARD-FISH. Furthermore, one-week bottle incubations amended with inorganic nutrients and carbon substrates (a mix of substrates, glutamine, Nacetylglucosamine, or pyruvate) revealed contrasting capacity of bacterioplankton to utilize specific carbon substrates in the iceberg-influenced waters compared with the undisturbed site. Our study demonstrates that the hydrographical perturbations introduced by a drifting iceberg can affect activity, composition, and substrate utilization capability of marine bacterioplankton. Consequently, in a context of global warming, increased frequency of drifting icebergs in polar regions holds the potential to affect carbon and nutrient biogeochemistry at local and possibly regional scales.
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| 4. |
- Leblond, Jeffrey D., et al.
(författare)
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A data mining approach to dinoflagellate clustering according to sterol composition : correlations with evolutionary history
- 2010
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Ingår i: International journal of data mining and bioinformatics. - 1748-5673. ; 4:4, s. 431-451
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Tidskriftsartikel (refereegranskat)abstract
- This study examined the sterol compositions of 102 dinoflagellates using clustering and cluster validation techniques, as a means of determining the relatedness of the organisms. In addition, dinoflagellate sterol-based relationships were compared statistically to 18S rDNA-based phylogenetic relationships using the Mantel test. Our results indicated that the examined dinoflagellates formed six clusters based on sterol composition and that several, but not all, dinoflagellate genera, which formed discrete clusters in the 18S rDNA-based phylogeny, shared similar sterol compositions. This and other correspondences suggest that the sterol compositions of dinoflagellates are explained, to a certain extent, by the evolutionary history of this lineage.
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| 5. |
- Leblond, J D, et al.
(författare)
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Fatty acid and sterol composition of two evolutionarily closely related dinoflagellate morphospecies from cold Scandinavian brackish and freshwaters
- 2006
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Ingår i: European Journal of Phycology. - : Informa UK Limited. - 1469-4433 .- 0967-0262. ; 41:3, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the lipid composition of cold-adapted dinoflagellates. Here, we investigate Peridinium aciculiferum and Scrippsiella hangoei, two cold-adapted dinoflagellate morphospecies that present significant differences in general morphology, physiology and habitat, but which share identical ribosomal DNA (rDNA) sequences, indicating a recent evolutionary divergence between them. Despite their present taxonomic names, it is now known that these two genetically isolated morphospecies are evolutionarily related to the so-called Pfiesteria-like species. We have found that chloroplast-associated glycolipids from P. aciculiferum and S. hangoei contained a higher relative percentage of two polyunsaturated C-18 fatty acids (octadecapentaenoic [18:5(n-3)] and octadecatetraenoic [18:4(n-3)] acids), and a lower relative percentage of hexadecanoic acid (16:0) than typically observed in previously examined warm-adapted dinoflagellate species. This suggests that these two fatty acids provided the requisite membrane fluidity for chloroplasts under a cold growth condition in these two organisms. A similar increase in 18:5(n-3) and 18:4(n-3) over warm-adapted species was also found in the phospholipids and triglycerides. P. aciculiferum and S. hangoei were also examined for the production of unique sterols that may serve as chemical biomarkers. Both were found to have a very similar sterol composition, consisting of two common dinoflagellate sterols, cholestanol and dinostanol, as dominant sterols, along with a number of other common dinoflagellate sterols as minor sterols. This demonstrated the absence of a specific steroidal biomarker but, more importantly, showed that these two morphospecies still produce very similar sterols despite having diverged in several other traits.
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| 6. |
- Logares, Ramiro, et al.
(författare)
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Biogeography of bacterial communities exposed to progressive long-term environmental change
- 2013
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 7:5, s. 937-948
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Tidskriftsartikel (refereegranskat)abstract
- The response of microbial communities to long-term environmental change is poorly understood. Here, we study bacterioplankton communities in a unique system of coastal Antarctic lakes that were exposed to progressive long-term environmental change, using 454 pyrosequencing of the 16S rDNA gene (V3-V4 regions). At the time of formation, most of the studied lakes harbored marine-coastal microbial communities, as they were connected to the sea. During the past 20 000 years, most lakes isolated from the sea, and subsequently they experienced a gradual, but strong, salinity change that eventually developed into a gradient ranging from freshwater (salinity 0) to hypersaline (salinity 100). Our results indicated that present bacterioplankton community composition was strongly correlated with salinity and weakly correlated with geographical distance between lakes. A few abundant taxa were shared between some lakes and coastal marine communities. Nevertheless, lakes contained a large number of taxa that were not detected in the adjacent sea. Abundant and rare taxa within saline communities presented similar biogeography, suggesting that these groups have comparable environmental sensitivity. Habitat specialists and generalists were detected among abundant and rare taxa, with specialists being relatively more abundant at the extremes of the salinity gradient. Altogether, progressive long-term salinity change appears to have promoted the diversification of bacterioplankton communities by modifying the composition of ancestral communities and by allowing the establishment of new taxa. The ISME Journal (2013) 7, 937-948; doi:10.1038/ismej.2012.168; published online 20 December 2012
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| 7. |
- Logares, Ramiro, et al.
(författare)
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Contrasting prevalence of selection and drift in the community structuring of bacteria and microbial eukaryotes
- 2018
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 20:6, s. 2231-2240
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Tidskriftsartikel (refereegranskat)abstract
- Whether or not communities of microbial eukaryotes are structured in the same way as bacteria is a general and poorly explored question in ecology. Here, we investigated this question in a set of planktonic lake microbiotas in Eastern Antarctica that represent a natural community ecology experiment. Most of the analysed lakes emerged from the sea during the last 6000 years, giving rise to waterbodies that originally contained marine microbiotas and that subsequently evolved into habitats ranging from freshwater to hypersaline. We show that habitat diversification has promoted selection driven by the salinity gradient in bacterial communities (explaining approximate to 72% of taxa turnover), while microeukaryotic counterparts were predominantly structured by ecological drift (approximate to 72% of the turnover). Nevertheless, we also detected a number of microeukaryotes with specific responses to salinity, indicating that albeit minor, selection has had a role in the structuring of specific members of their communities. In sum, we conclude that microeukaryotes and bacteria inhabiting the same communities can be structured predominantly by different processes. This should be considered in future studies aiming to understand the mechanisms that shape microbial assemblages.
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| 8. |
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| 9. |
- Logares, Ramiro, et al.
(författare)
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Extensive dinoflagellate phylogenies indicate infrequent marine-freshwater transitions
- 2007
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1095-9513 .- 1055-7903. ; 45:3, s. 887-903
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Tidskriftsartikel (refereegranskat)abstract
- We have constructed extensive 18S–28S rDNA dinoflagellate phylogenies (>200 sequences for each marker) using Maximum Likelihood and Bayesian Inference to study the evolutionary relationships among marine and freshwater species (43 new sequences). Our results indicated that (a) marine and freshwater species are usually not closely related, (b) several freshwater species cluster into monophyletic groups, (c) most marine–freshwater transitions do not seem to have occurred recently and, (d) only a small fraction of the marine lineages seem to have colonized fresh waters. Thus, it becomes apparent that the marine–freshwater boundary has acted as a barrier during the evolutionary diversification of dinoflagellates. Our results also shed light on the phylogenetic positions of several freshwater dinoflagellates which, to date, were uncertain.
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| 10. |
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