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- Sopanen, S, et al.
(författare)
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Prymnesium parvum exotoxins affect the grazing and viability of the calanoid copepod Eurytemora affinis
- 2008
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 361, s. 191-202
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Tidskriftsartikel (refereegranskat)abstract
- The calanoid copepod Eurytemora affinis from the northern Baltic Sea was exposed to cell-free filtrates of the toxic haptophyte Prymnesium parvum as well as to cell mixtures of P. parvum and Rhodomonas salina. To test the effects of P. parvum exudates and allelopathy on selective grazers, copepods were incubated (1) in increasing concentrations of cell-free filtrates of P. parvum in the presence of good food (R, salina), (2) in 1:1 cell mixtures at 2 cell concentrations of P. parvum and R. salina and (3) in R. salina cell suspension, which was used as a control for good-quality food. P. parvum cultures were grown in nutrient-balanced (+NP) or limited (-N or -P) media to obtain different levels of toxicity. Survival, ingestion, faecal pellet production rates and egg production were measured over 3 d, together with measurements of P. parvum toxicity (hemolytic activity) (HA). Most of the copepods incubated in high-filtrate concentrations died or became severely impaired, although (HA) in filtrates was under the detection limit. Further, the ingestion and faecal pellet production rates were suppressed in the highest filtrate concentrations in nutrient-limited treatments. Higher cell density in cell mixtures resulted in significantly lower faecal pellet production, although survival remained high. Our results show that HA is not a good overall indicator of the total harmful effects of P. parvum on grazers. Besides monospecific P. parvum diets, filtrates and cell mixtures have negative effects on grazers, and these effects are stronger under nutrient-depleted conditions; however, the presence of good-quality food lowers harmful effects for copepods. The negative effects caused either by direct intoxication or by food limitation following from strong allelopathic effects of P. parvum on other components of nano- and microplankton suggest that P. parvum blooms have a realistic potential to be deleterious for copepod secondary production, irrespective of the presence of alternative food sources.
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- Sopanen, S, et al.
(författare)
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Toxic haptophyte Prymnesium parvum affects grazing, survival, egestion and egg production of the calanoid copepods Eurytemora affinis and Acartia bifilosa
- 2006
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 327, s. 223-232
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen- and phosphorus-depleted or NP-balanced toxic haptophyte Prymnesium parvum was fed to 2 dominant copepod species of the northern Baltic Sea (Eurytemora affinis and Acartia bifflosa), and their ingestion, egg and faecal pellet production rates and mortality were measured. The copepods were incubated in 5 different cell concentrations of P. parvum for 3 consecutive days; the cryptophyte Rhodomonas salina was used as a control for non-toxic, nutritionally high-quality food. Toxicity (haemolytic activity) of P. parvum was measured before and after the incubations. The haemolytic activity of R parvum was the highest in cultures grown under nutrient deficiency. The toxicity decreased after 1 d incubation in all treatments, in both the presence and absence of copepods. Neither of the copepod species ingested R parvum, irrespective of the nutrient treatment (toxicity) or cell concentration, and the pellet and egg production rates were correspondingly low. Although there was no significant increase in mortality in P. parvum treatments, copepods that were exposed to P. parvum in any concentration or nutrient treatment soon became inactive. It was evident that the toxicity of even nutrient-replete P. parvum had an indirect and sublethal influence on copepods, although this could not be measured as short-term increased mortality. Our results suggest a strong reduction in secondary production of copepods in an event of a P. parvum bloom.
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- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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- Gyllenberg, M, et al.
(författare)
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New methods for the analysis of binarized BIOLOG GN data of vibrio species : Minimization of stochastic complexity and cumulative classification
- 2002
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Ingår i: Systematic and Applied Microbiology. - : Elsevier BV. - 0723-2020 .- 1618-0984. ; 25:3, s. 403-415
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Tidskriftsartikel (refereegranskat)abstract
- We apply minimization of stochastic complexity and the closely related method of cumulative classification to analyse the extensively studied BIOLOG GN data of Vibrio spp. Minimization of stochastic complexity provides an objective tool of bacterial taxonomy as it produces classifications that are optimal from the point of view of information theory. We compare the outcome of our results with previously published classifications of the same data set. Our results both confirm earlier detected relationships between species and discover new ones.
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- Lissner, Lauren, 1956, et al.
(författare)
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Statement by Members of the Task Force on Prevention and Public Health of the European Association for the Study of Obesity (EASO)
- 2009
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Ingår i: Obesity Facts. - 1662-4025. ; 2:1, s. 54-55
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Tidskriftsartikel (refereegranskat)abstract
- This document is signed by all members of the task force, who will contribute knowledge on the problem of obesity in the various regions of Europe. It is apparent from the wide range of available prevalence estimates that the magnitude of the obesity epidemic varies across Europe. However certain similarities are present, including consistent but varying increases in prevalence in all countries from the end of the 20th century to the present, together with clear inverse socioeconomic gradients. The lack of harmonized surveillance efforts across Europe makes international monitoring and comparative assessments imprecise at best. A particularly worrisome aspect of this epidemic is the recently observed increase in the proportion of European children with overweight and obesity. The Task Force is in agreement that the epidemic reflects changing lifestyles and environments and that prevention can only be achieved by identifying and arresting these trends, a statement that has been repeated by many groups advocating obesity prevention over the years. For instance, in 1999 the Milan Declaration was made on behalf of all members of the EASO, resolving to support the development of coherent national and Europe-wide strategies for the prevention and management of overweight and obesity. Since then, there have been recent steps to develop a public health strategy for obesity prevention across Europe, including most notably the 2006 European Ministerial Conference on Counteracting Obesity in the European Region. At that time, all member states of WHO Europe met in Istanbul and explicitly agreed on an ecological approach to fighting the obesity epidemic, with a charter recognizing that counteracting obesity requires a multidisciplinary effort with a timeline for improvements (www.euro.who.int/ document/E89567.pdf). In this context, the vision of our Task Force is to provide guidance and leadership to researchers, governments, and agencies that are trying to fulfill the charter developed in Istanbul and other recent initiatives. Specifically, we will support and strengthen research and interventions to improve prevention of obesity across Europe, within the framework of the EASO.
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