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- Dupont, Chris L., et al.
(författare)
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Functional Tradeoffs Underpin Salinity-Driven Divergence in Microbial Community Composition
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:2, s. e89549-
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial community composition and functional potential change subtly across gradients in the surface ocean. In contrast, while there are significant phylogenetic divergences between communities from freshwater and marine habitats, the underlying mechanisms to this phylogenetic structuring yet remain unknown. We hypothesized that the functional potential of natural bacterial communities is linked to this striking divide between microbiomes. To test this hypothesis, metagenomic sequencing of microbial communities along a 1,800 km transect in the Baltic Sea area, encompassing a continuous natural salinity gradient from limnic to fully marine conditions, was explored. Multivariate statistical analyses showed that salinity is the main determinant of dramatic changes in microbial community composition, but also of large scale changes in core metabolic functions of bacteria. Strikingly, genetically and metabolically different pathways for key metabolic processes, such as respiration, biosynthesis of quinones and isoprenoids, glycolysis and osmolyte transport, were differentially abundant at high and low salinities. These shifts in functional capacities were observed at multiple taxonomic levels and within dominant bacterial phyla, while bacteria, such as SAR11, were able to adapt to the entire salinity gradient. We propose that the large differences in central metabolism required at high and low salinities dictate the striking divide between freshwater and marine microbiomes, and that the ability to inhabit different salinity regimes evolved early during bacterial phylogenetic differentiation. These findings significantly advance our understanding of microbial distributions and stress the need to incorporate salinity in future climate change models that predict increased levels of precipitation and a reduction in salinity.
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- Akner, Gunnar, 1953-, et al.
(författare)
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Vi står gärna bakom en utfallsbaserad vård
- 2017
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Ingår i: Dagens Samhälle. - 1652-6511.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Jörgen Nordenström försöker få det till att vår kritik av värdebaserad vård egentligen handlar om att vi vill ha mer resurser. Han har helt missuppfattat oss, skriver 26 specialistläkare i en replik.
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- Granéli, Edna, et al.
(författare)
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The ecophysiology and bloom dynamics of Prymnesium spp.
- 2012
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 14:SI, s. 260-270
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Tidskriftsartikel (refereegranskat)abstract
- Members of Prymnesium belong to the division Haptophyta, class Prymnesiophyceae, order Prymnesialesand family Prymnesiaceae. As most haptophytes, members of the genus Prymnesium are unicellular andplanktonic. The most known of these species is the ichthyotoxic P. parvum, which may form nearlymonospecific dense blooms in coastal and inland waters. This species possesses extraordinary plasticityconcerning life survival strategies, and is specifically addressed in this review.Toxins produced by P. parvum have hemolytic properties, that not only kill fish but also co-existingplankton. These substances are allelopathic (when other algae are killed) and grazer deterrent (whengrazers are killed). Allelopathy enables P. parvum to utilize inorganic nutrients present in the surroundingwater without competition from other algal species; and by eliminating its grazers P. parvum reduces celllosses. The paralized microalgae and/or zooplankton, are therefter ingested by the P. parvum cells, aprocess called phagotrophy. P. parvum is also able of osmotrophy, i.e. utilization of dissolved organicmatter. In this review, the cellular characteristics, life cycles, bloom formation, and factors affectingtoxicity, allelopathy, phagotrophy, and osmotrophy of P. parvum are discussed.
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- Hagström, Johannes, et al.
(författare)
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Domoic acid production and elemental composition of two Pseudo-nitzschia multiseries strains, from the NW and SW Atlantic Ocean, growing in phosphorus- or nitrogen-limited chemostat cultures.
- 2011
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 33:2, s. 297-308
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Tidskriftsartikel (refereegranskat)abstract
- Here we compare cell physiology and domoic acid (DA) production for two strains of the diatom Pseudo-nitzschia multiseries originating from two opposite latitudes: Canada (CA) and Brazil (BR). The algae were grown as chemostat cultures at 0.2, 0.3 and 0.4 day−1 under nitrogen (N)- and phosphorus (P)-deficient conditions. The level of deficiency significantly affected the atomic C:N, C:P, C:Si and N:P ratios in both strains. In both strains, P per cell was 2–4× higher in the N- than in the P-deficient cultures. The opposite was not found for N in the P-deficient cultures, as shown by the N:P ratios and C:N ratios. The C:N and C:P ratios were significantly lower in the CA strain, and this did not change due to the level of deficiency. The concentration and production of DA per cell per day were significantly higher for both strains under P deficiency as expected since the toxin is rich in N. However, DA was also produced by both strains during continuous cell division under N deficiency. High or low bacterial densities associated with P. multiseries did not increase or decrease DA production. Our data imply that more attention needs to be given to the N:P ratios and concentrations in the waters where these algae occur, as both N and P deficiencies affect DA production and cellular DA concentrations.
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- Hagström, Johannes, et al.
(författare)
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Potential methods for managing Prymnesium parvum blooms and toxicity, with emphasis on clay and barley straw: A review
- 2010
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Ingår i: Journal of the American Water Resources Association. - : Wiley. - 1093-474X .- 1752-1688. ; 46:1, s. 187-198
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Tidskriftsartikel (refereegranskat)abstract
- Harmful algal bloom (HAB) control and mitigation is a complex problem in ecosystem management. Phytoplankton play an important role in aquatic ecosystems as primary producers and food sources for many commercially important shellfish and there are limited options for targeting just a single species within the community. Chemical treatments (e.g., algaecides), rotting barley straw, nitrogen and phosphorus manipulation, and clay and/or flocculants are but a few techniques tested or used to reduce fish kills or shellfish contamination during a HAB event. Prymnesium parvum control has focused on the use of chemicals, nutrient manipulation, and clay flocculation. However, many HAB control methods have been rejected due to their effects on ecosystems, high costs, or limited effects on target organisms. For example, rotting barley straw (Hordeum vulgare) is considered to be an environmentally friendly alternative, but has been found to have very different results on the phytoplankton community depending on the dominating taxa and is ineffective against P. parvum and dinoflagellate blooms. Clay flocculation is a useful control/mitigation technique during fish kills in marine aquaculture sites in South Korea and can be effective in freshwater if the correct combination of clay and flocculent is used. Toxins produced by P. parvum and Karenia brevis also bind to phosphatic clay, thereby removing and/or neutralizing the toxins, but there is concern that the clay will have a negative effect on sessile organisms. Some shellfish suffer high mortalities and significant impacts on somatic and reproductive tissue growth at high clay loads; however, benthic communities appear to be unchanged after five years of clay treatment in South Korea. There are likely site-specific and ecosystem-specific characteristics that make generalizations about control options difficult and require careful assessment of options at each location.
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