Characterization and temperature dependence of Arctic Micromonas polaris viruses

Global climate change-induced warming of the Artic seas is predicted to shift the phytoplankton community towards dominance of smaller-sized species due to global warming. Yet, little is known about their viral mortality agents despite the ecological importance of viruses regulating phytoplankton host dynamics and diversity. Here we report the isolation and basic characterization of four prasinoviruses infectious to the common Arctic picophytoplankter Micromonas. We furthermore assessed how temperature influenced viral infectivity and production. Phylogenetic analysis indicated that the putative double-stranded DNA (dsDNA) Micromonas polaris viruses (MpoVs) are prasinoviruses (Phycodnaviridae) of approximately 120 nm in particle size. One MpoV showed intrinsic differences to the other three viruses, i.e., larger genome size (205 ± 2 vs. 191 ± 3 Kb), broader host range, and longer latent period (39 vs. 18 h). Temperature increase shortened the latent periods (up to 50%), increased the burst size (up to 40%), and affected viral infectivity. However, the variability in response to temperature was high for the different viruses and host strains assessed, likely affecting the Arctic picoeukaryote community structure both in the short term (seasonal cycles) and long term (global warming)

Atlantic Advection Driven Changes in Glacial Meltwater: Effects on Phytoplankton Chlorophyll-a and Taxonomic Composition in Kongsfjorden, Spitsbergen

Phytoplankton biomass and composition was investigated in a high Arctic fjord (Kongsfjorden, 79◦N, 11◦40′E) using year round weekly pigment samples collected from October 2013 to December 2014. In addition, phytoplankton dynamics supplemented with physical and chemical characteristics of the 2014 spring bloom (April–June 2014) were assessed in two locations in Kongsfjorden. The goal was to elucidate effects of Atlantic advection on spatial phytoplankton chlorophyll-a (chl-a) and taxonomic composition. Chl-a declined during the polar night to a minimum of 0.01mg m−3, followed by a 1000-fold increase until May 28. Atlantic advection prevented sea ice formation and increased springtime melting of marine terminating glaciers. This coincided with spatial and temporal differences in abundances of flagellates (prasinophytes, haptophytes, cryptophytes, and chrysophytes) and diatoms in early spring. More flagellated phytoplankton were observed in the non-stratified central Kongsfjorden, whereas diatoms were more abundant in the stratified inner fjord. Contrasting conditions between locations were reduced when glacial melt water stratification expanded toward the mouth of the fjord, mediating a diatom dominated surface bloom at both locations. We suggest that glacial melt water governs spring bloom spatial timing and composition in the absence of sea ice driven stratification. The spring bloom exhausted surface nutrient concentrations by the end of May. The nutrient limited post bloom period (June–October) was characterized by reduced biomass and pigments of flagellated phytoplankton, consisting of prasinophytes, haptophytes, chrysophytes, and to a lesser extent cryptophytes and peridinin-containing dinoflagellates

Metabolic background determines the importance of NOS3 polymorphisms in restenosis after percutaneous coronary intervention:A study in patients with and without the metabolic syndrome

Variation in the NOS3 gene has been related to the development of restenosis. The Glu298Asp polymorphism has previously been investigated for its effect on NO levels and the development of restenosis. However, the variability of findings gave rise to the hypothesis that the functional significance of this polymorphism may only become manifest under conditions of endothelial dysfunction. Since patients with the metabolic syndrome are known to have endothelial dysfunction, we aimed to investigate if the significance of NOS3 polymorphisms may depend on the presence of the metabolic syndrome

Physical, chemical, and biological water column characteristics from April to June 2014 of Kongsfjorden (Spitsbergen)

Physical, chemical, and biological water column (upper 100 m) characteristics of Kongsfjorden (Spitsbergen) were measured from April to June 2014 at 3 stations. Profiles of temperature, salinity, irradiance chlorophyll fluorescence and turbidity were obtained by CTD. Nuntrient concentrations (phosphate, nitrate, ammonium, and silicate) and phytoplankton characteristics were measured in samples obtained by Niskin bottle. Phytoplankton pigments were determined by HPLC. Phytoplankton composition was calculated from marker pigments using CHEMTAX

Chemical and biological water column characteristics from April to June 2014 in Kongsfjorden (Spitsbergen)

Physical, chemical, and biological water column (upper 100 m) characteristics of Kongsfjorden (Spitsbergen) were measured from April to June 2014 at 3 stations. Profiles of temperature, salinity, irradiance chlorophyll fluorescence and turbidity were obtained by CTD. Nuntrient concentrations (phosphate, nitrate, ammonium, and silicate) and phytoplankton characteristics were measured in samples obtained by Niskin bottle. Phytoplankton pigments were determined by HPLC. Phytoplankton composition was calculated from marker pigments using CHEMTAX

Physical water column characteristics from April to June 2014 in Kongsfjorden (Spitsbergen)

Coverage: EVENT LABEL: * LATITUDE: 78.945650 * LONGITUDE: 12.018810 * DATE/TIME START: 2014-04-09T00:00:00 * DATE/TIME END: 2014-06-10T00:00:00 * LOCATION: Kongsfjorden, Spitsbergen, Arctic * CAMPAIGN: JF2014 * BASIS: Jean Floch * DEVICE: CTD/Rosette EVENT LABEL: * LATITUDE: 78.905710 * LONGITUDE: 12.375480 * DATE/TIME START: 2014-04-09T00:00:00 * DATE/TIME END: 2014-06-10T00:00:00 * LOCATION: Kongsfjorden, Spitsbergen, Arctic * CAMPAIGN: JF2014 * BASIS: Jean Floch * DEVICE: CTD/Rosette EVENT LABEL: * LATITUDE: 79.007960 * LONGITUDE: 11.308910 * DATE/TIME START: 2014-04-20T00:00:00 * DATE/TIME END: 2014-05-10T00:00:00 * LOCATION: Kongsfjorden, Spitsbergen, Arctic * CAMPAIGN: JF2014 * BASIS: Jean Floch * DEVICE: CTD/Rosett

Chemical and biological water column characteristics from April to June 2014 in Kongsfjorden (Spitsbergen)

Coverage: EVENT LABEL: * LATITUDE: 78.945650 * LONGITUDE: 12.018810 * DATE/TIME START: 2014-04-09T00:00:00 * DATE/TIME END: 2014-06-10T00:00:00 * LOCATION: Kongsfjorden, Spitsbergen, Arctic * CAMPAIGN: JF2014 * BASIS: Jean Floch * DEVICE: CTD/Rosette EVENT LABEL: * LATITUDE: 78.905710 * LONGITUDE: 12.375480 * DATE/TIME START: 2014-04-09T00:00:00 * DATE/TIME END: 2014-06-10T00:00:00 * LOCATION: Kongsfjorden, Spitsbergen, Arctic * CAMPAIGN: JF2014 * BASIS: Jean Floch * DEVICE: CTD/Rosette EVENT LABEL: * LATITUDE: 79.007960 * LONGITUDE: 11.308910 * DATE/TIME START: 2014-04-20T00:00:00 * DATE/TIME END: 2014-05-10T00:00:00 * LOCATION: Kongsfjorden, Spitsbergen, Arctic * CAMPAIGN: JF2014 * BASIS: Jean Floch * DEVICE: CTD/Rosett

Influence of Irradiance and Temperature on the Virus MpoV-45T Infecting the Arctic Picophytoplankter <i>Micromonas polaris</i>

Arctic marine ecosystems are currently undergoing rapid changes in temperature and light availability. Picophytoplankton, such as Micromonas polaris, are predicted to benefit from such changes. However, little is known about how these environmental changes affect the viruses that exert a strong mortality pressure on these small but omnipresent algae. Here we report on one-step infection experiments, combined with measurements of host physiology and viability, with 2 strains of M. polaris and the virus MpoV-45T under 3 light intensities (5, 60 and 160 &#956;mol quanta m&#8722;2 s&#8722;1), 2 light period regimes (16:8 and 24:0 h light:dark cycle) and 2 temperatures (3 and 7 &#176;C). Our results show that low light intensity (16:8 h light:dark) delayed the decline in photosynthetic efficiency and cell lysis, while decreasing burst size by 46%. In contrast, continuous light (24:0 h light:dark) shortened the latent period by 5 h for all light intensities, and even increased the maximum virus production rate and burst size under low light (by 157 and 69%, respectively). Higher temperature (7 &#176;C vs 3 &#176;C) led to earlier cell lysis and increased burst size (by 19%), except for the low light conditions. These findings demonstrate the ecological importance of light in combination with temperature as a controlling factor for Arctic phytoplankton host and virus dynamics seasonally, even more so in the light of global warming

Genome-Wide Association Studies of Ischemic Stroke

The intact polar lipid (IPL) composition of phytoplankton is plastic and dependent on environmental factors. Previous studies have shown that phytoplankton under low phosphorus (P) availability substitutes phosphatidylglycerols (PGs) with sulfoquinovosyldiacylglycerols (SQDGs) and digalactosyldiacylglycerols (DGDGs). However, these studies focused merely on P depletion, while phytoplankton in the natural environment often experience P limitation whereby the strength depends on the supply rate of the limiting nutrient. Here we report on the IPL composition of axenic cultures of the picophotoeukaryote Micromonas pusilla under different degrees of P limitation, i.e., P-controlled chemostats at 97 and 32 % of the maximum growth rate, and P starvation (obtained by stopping P supply to these chemostats). P-controlled cultures were also grown at elevated partial carbon dioxide pressure (pCO2) to mimic a future scenario of strengthened vertical stratification in combination with ocean acidification. Additionally, we tested the influence of viral infection for this readily infected phytoplankton host species. Results show that both SQDG : PG and DGDG : PG ratios increased with enhanced P limitation. Lipid composition was, however, not affected by enhanced (750 vs. 370 µatm) pCO2. In the P-starved virally infected cells the increase in SQDG : PG and DGDG : PG ratios was lower, whereby the extent depended on the growth rate of the host cultures before infection. The lipid membrane of the virus MpV-08T itself lacked some IPLs (e.g., monogalactosyldiacylglycerols; MGDGs) in comparison with its host. This study demonstrates that, besides P concentration, also the P supply rate, viral infection and even the history of the P supply rate can affect phytoplankton lipid composition (i.e., the non-phospholipid : phospholipid ratio), with possible consequences for the nutritional quality of phytoplankton