scholarly journals Mechanisms of <i>Trichodesmium</i> bloom demise within the New Caledonia Lagoon during the VAHINE mesocosm experiment

2016 ◽  
Author(s):  
D. Spungin ◽  
U. Pfreundt ◽  
H. Berthelot ◽  
S. Bonnet ◽  
D. AlRoumi ◽  
...  
Keyword(s):  
Surface Waters ◽  
New Caledonia ◽  
Specific Activity ◽  
Rapid Decline ◽  
Ambient Conditions ◽  
Nutrient Storage ◽  
Cellular Processes ◽  
Extensive Surface ◽  
High Concentrations ◽  
Transparent Exopolymeric Particles

Abstract. The globally important marine diazotrophic cyanobacterium Trichodesmium blooms regularly in the New Caledonian lagoons (Sowthwestern Pacific). We exploited the development of a Trichodesmium bloom in the lagoon waters outside the enclosed VAHINE mesocosms to specifically investigate the cellular processes mediating its decline. Trichodesmium cells (and associated microbiota) were sampled from the time of surface accumulation to biomass demise using a series of enclosed incubations to elucidate the stressors and subcellular underpinning of rapid (~ 24 h) biomass demise and disappearance. The development and decline of Trichodesmium populations was rapid with extensive surface accumulations (blooms) appearing within 24 h on the surface waters of the lagoon. Rapid decline of > 90 % biomass after 24 h of peak accumulation was observed in p opulations that were collected and incubated under ambient conditions. Metatranscriptomic profiling of Trichodesmium biomass 8 h and 22 h after bottle incubation of surface accumulations revealed evidence for phosphorus (P) and iron (Fe) stress, with upreg ulation of genes required to increase their availability and transport. In contrast, genes responsible for nutrient storage were downregulated. Total viral abundance, assessed by SYBR-green staining and analytical flow cytometry, oscillated throughout the experiment and showed no significant relationship with Trichodesmium bloom development or demise. Enhanced caspase-specific activity and upregulation of a suite of metacaspase genes during bloom demise implicated autocatalytic programmed cell death (PCD) as the mechanistic cause. At the same time, genes associated with buoyancy and gas-vesicle production were strongly downregulated concomitant with high concentrations of transparent exopolymeric particles (TEP), greatly aiding aggregation and expediting vertical flux to depth. Our results demonstrate that the rapid demise of this high-density, Trichodesmium surface bloom over 24 h was not caused by specific lytic infection but was rather induced by PCD in response to combined nutrient and oxidative stressors.

scholarly journals Mechanisms of <i>Trichodesmium</i> demise within the New Caledonian lagoon during the VAHINE mesocosm experiment

2016 ◽  
Vol 13 (14) ◽  
pp. 4187-4203 ◽  
Author(s):  
Dina Spungin ◽  
Ulrike Pfreundt ◽  
Hugo Berthelot ◽  
Sophie Bonnet ◽  
Dina AlRoumi ◽  
...  
Keyword(s):  
Specific Activity ◽  
Ambient Conditions ◽  
Nutrient Storage ◽  
Viral Abundance ◽  
Austral Spring ◽  
Cellular Processes ◽  
Expression Of Genes ◽  
High Concentrations ◽  
Transparent Exopolymeric Particles

Abstract. The globally important marine diazotrophic cyanobacterium Trichodesmium is abundant in the New Caledonian lagoon (southwestern Pacific Ocean) during austral spring/summer. We investigated the cellular processes mediating Trichodesmium mortality from large surface accumulations (blooms) in the lagoon. Trichodesmium cells (and associated microbiota) were collected at the time of surface accumulation, enclosed under simulated ambient conditions, and sampled over time to elucidate the stressors and subcellular underpinning of rapid biomass demise (> 90 % biomass crashed within  ∼  24 h). Metatranscriptomic profiling of Trichodesmium biomass, 0, 8 and 22 h after incubations of surface accumulations, demonstrated upregulated expression of genes required to increase phosphorus (P) and iron (Fe) availability and transport, while genes responsible for nutrient storage were downregulated. Total viral abundance oscillated throughout the experiment and showed no significant relationship with the development or demise of the Trichodesmium biomass. Enhanced caspase-specific activity and upregulated expression of a suite of metacaspase genes, as the Trichodesmium biomass crashed, implied autocatalytic programmed cell death (PCD) as the mechanistic cause. Concurrently, genes associated with buoyancy and gas vesicle production were strongly downregulated concomitant with increased production and high concentrations of transparent exopolymeric particles (TEP). The rapid, PCD-mediated, decline of the Trichodesmium biomass, as we observed from our incubations, parallels mortality rates reported from Trichodesmium blooms in situ. Our results suggest that, whatever the ultimate factor, PCD-mediated death in Trichodesmium can rapidly terminate blooms, facilitate aggregation, and expedite vertical flux to depth.

Bank filtration: a suitable process for the removal of iodinated X-ray contrast media?

2004 ◽  
Vol 50 (5) ◽  
pp. 261-268 ◽  
Author(s):  
S. Schittko ◽  
A. Putschew ◽  
M. Jekel
Keyword(s):  
Drinking Water ◽  
Contrast Media ◽  
Surface Waters ◽  
Sampling Period ◽  
Transformation Products ◽  
Bank Filtration ◽  
Anoxic Conditions ◽  
X Ray ◽  
High Concentrations ◽  
Media Concentration

After bank filtration, effluent influenced surface waters are often used as raw drinking water. It is known that high concentrations of iodinated X-ray contrast media are detectable in such surface waters and thus, more knowledge about the behaviour of the contrast media during bank filtration is necessary and the subject of investigations in this study. The adsorbable organic iodine (AOI), four widely used iodinated X-ray contrast media and four possible transformation products were quantified in an influenced lake, five groundwater wells and a drinking water well. Under anoxic conditions the AOI as well as the concentration of the contrast media are decreased by bank filtration, whereby the AOI is decreased by 64% and the contrast media concentration can be reduced up to 95%, depending on the compound. In the raw drinking water the following average concentrations were determined: Iopromid &lt;20 ng/L, Diatrizote 166 ng/L, Iopamidol 166 ng/L and Iohexol 34 ng/L. Instationary conditions during the sampling period indicate that, at least under anoxic conditions, a large part of the contrast media and transformation products, which are still iodinated, may be associated to colloids and/or humic material.

Binding of 3-phosphoglycerate leads to both activation and stabilisation of ADP-glucose pyrophosphorylase from apple leaves

2005 ◽  
Vol 32 (9) ◽  
pp. 839
Author(s):  
Rui Zhou ◽  
Lailiang Cheng
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Enzyme Activity ◽  
Inorganic Phosphate ◽  
Thermal Inactivation ◽  
Specific Activity ◽  
Apple Leaves ◽  
Apparent Homogeneity ◽  
Adp Glucose Pyrophosphorylase ◽  
High Concentrations

Apple leaf ADP-glucose pyrophosphorylase was purified 1436-fold to apparent homogeneity with a specific activity of 58.9 units mg–1. The enzyme was activated by 3-phosphoglycerate (PGA) and inhibited by inorganic phosphate (Pi) in the ADPG synthesis direction. In the pyrophosphorolytic direction, however, high concentrations of PGA (> 2.5 mm) inhibited the enzyme activity. The enzyme was resistant to thermal inactivation with a T0.5 (temperature at which 50% of the enzyme activity is lost after 5 min incubation) of 52°C. Incubation with 2 mm PGA or 2 mm Pi increased T0.5 to 68°C. Incubation with 2 mm dithiothreitol (DTT) decreased T0.5 to 42°C, whereas inclusion of 2 mm PGA in the DTT incubation maintained T0.5 at 52°C. DTT-induced decrease in thermal stability was accompanied by monomerisation of the small subunits. Presence of PGA in the DTT incubation did not alter the monomerisation of the small subunits of the enzyme induced by DTT. These findings indicate that binding of PGA renders apple leaf AGPase with a conformation that is not only more efficient in catalysis but also more stable to heat treatment. The physiological significance of the protective effect of PGA on thermal inactivation of AGPase is discussed.

scholarly journals Ribonucleic acid stimulation of mammalian liver nuclear-envelope nucleoside triphosphatase. A possible enzymic marker for the nuclear envelope

1977 ◽  
Vol 162 (3) ◽  
pp. 671-679 ◽  
Author(s):  
P S Agutter ◽  
J R Harris ◽  
I Stevenson
Keyword(s):  
Nuclear Envelope ◽  
Specific Activity ◽  
Assay Medium ◽  
Exogenous Rna ◽  
Mammalian Liver ◽  
High Concentrations ◽  
Enzymic Marker ◽  
Stimulation Of ◽  
Nucleoside Triphosphatase

1. The specific activity of rat and pig liver nuclear-envelope nucleoside triphosphatase (EC 3.6.1.3) decreases when the system is depleted of RNA. The activity can be restored by adding high concentrations of yeast RNA to the assay medium. 2. Exogenous RNA also increases the activity of the enzyme in control envelopes (not RNA-depleted). The effect appears to be largely specific for poly(A) and poly(G); it is not stimulated by rRNA or tRNA preparations, ribonuclease-hydrolysed RNA, AMP, or double- or single-stranded DNA. 3. Inhibitors of the enzyme, in concentrations at which half-maximal inhibition of the enzyme is achieved, do not affect the percentage stimulation of the enzyme by yeast RNA. 4. The simulation is abolished by the inclusion of 150 mM-KCl or -NaCl in the assay medium, but not by increasing the assay pH to 8.5. 5. The results are discussed in the light of the possible role of the nucleoside triphosphatase in vivo in nucleo-cytoplasmic ribonucleoprotein translocation. 6. It is proposed that poly(G)-stimulated Mg2+-activated adenosine triphosphatase activity should be adopted as an enzymic marker for the nuclear envelope.

The influence of hydrological pathways on the transport of the herbicide, isoproturon, through an underdrained clay soil

1999 ◽  
Vol 39 (12) ◽  
pp. 77-84 ◽  
Author(s):  
C. M. Heppell ◽  
T. P. Burt ◽  
R. J. Williams ◽  
A. H. Haria
Keyword(s):  
Surface Waters ◽  
Clay Soil ◽  
Quality Standard ◽  
Early Spring ◽  
Hydrological Response ◽  
Macropore Flow ◽  
Ephemeral Stream ◽  
Low Intensity ◽  
Flow Through ◽  
High Concentrations

This paper reports the findings of a 12 month field monitoring programme at Wytham (Oxfordshire, UK), which examined the leaching of the phenylurea herbicide, isoproturon, from an agricultural clay hillslope to the adjacent ephemeral stream. Isoproturon was shown to reach the drains (at 50 cm depth) through a combination of vertical and lateral macropore flow through wormholes and inter-pedal cracks. Seasonal changes in hydrological response were also observed at the site, with lateral flow through inter-pedal cracks providing an important route by which herbicide was transported during autumn and early spring when the clay soils were wetting up. Concentrations of isoproturon in drainflow frequently exceeded the Environment Agency's (EA) non-statutory Environmental Quality Standard (EQS) of 20 μg/l for isoproturon in surface waters. Even under low intensity rainfall (&lt; 1 mm/hr) the saturated region at the base of the hillslope was shown to conduct macropore flow containing significantly high concentrations of herbicide to the drain. The results of this study suggest that those regions close to surface waters which are areas of converging hydrological flow may be key contributors to the problem of isoproturon contamination of surface waters.

scholarly journals Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development

2009 ◽  
Vol 6 (2) ◽  
pp. 3803-3850 ◽  
Author(s):  
E. Breitbarth ◽  
J. Gelting ◽  
J. Walve ◽  
L. J. Hoffmann ◽  
D. R. Turner ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Surface Waters ◽  
Cyanobacterial Bloom ◽  
Euphotic Zone ◽  
Strong Wind ◽  
Ferrous Ions ◽  
The Baltic Sea ◽  
High Concentrations ◽  
Wind Events ◽  
The Baltic

Abstract. Iron chemistry measurements were conducted during summer 2007 at two distinct locations in the Baltic Sea (Gotland Deep and Landsort Deep) to evaluate the role of iron for cyanobacterial bloom development in these estuarine waters. Depth profiles of Fe(II) were measured by chemiluminescent flow injection analysis (CL-FIA) and reveal several origins of Fe(II) to the water column. Photoreduction of Fe(III)-complexes and deposition by rain are main sources of Fe(II) (up to 0.9 nmol L−1) in light penetrated surface waters. Indication for organic Fe(II) complexation resulting in prolonged residence times in oxygenated water was observed. Surface dwelling heterocystous cyanobacteria where mainly responsible for Fe(II) consumption in comparison to other phytoplankton. The significant Fe(II) concentrations in surface waters apparently play a major role in cyanobacterial bloom development in the Baltic Sea and are a major contributor to the Fe requirements of diazotrophs. Second, Fe(II) concentrations up to 1.44 nmol L−1 were observed at water depths below the euphotic zone, but above the oxic anoxic interface. Finally, all Fe(III) is reduced to Fe(II) in anoxic deep water. However, only a fraction thereof is present as ferrous ions (up to 28 nmol L−1) and was detected by the CL-FIA method applied. Despite their high concentrations, it is unlikely that ferrous ions originating from sub-oxic waters could be a temporary source of bioavailable iron to the euphotic zone since mixed layer depths after strong wind events are not deep enough in summer time.

scholarly journals Exposure of the Main Italian River Basin to Pharmaceuticals

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Federico Ferrari ◽  
Agata Gallipoli ◽  
Matteo Balderacchi ◽  
Maria M. Ulaszewska ◽  
Ettore Capri ◽  
...  
Keyword(s):  
Surface Waters ◽  
Point Sources ◽  
Preliminary Survey ◽  
Italian Economy ◽  
Sediment Samples ◽  
Pharmaceutical Contamination ◽  
Low Levels ◽  
High Concentrations ◽  
River Po ◽  
Sources Of Contamination

This study give a preliminary survey of pharmaceutical contamination and accumulation in surface waters and sediments along the river Po basin (74,000 km2, the largest in Italy), a strategic region for the Italian economy: it collects sewage from a vast industrialized area of Italy (Autorità di Baciono del fiume Po, 2006, 2009). 10 pharmaceuticals (atenolol, propanolol, metoprolol, nimesulide, furosemide, carbamazepine, ranitidine, metronidazole, paracetamol, and atorvastatin) from several therapeutic classes were searched in 54 sampling points along the river Po from the source to the delta, and at the mouth of its major effluents. In water samples were found pharmaceuticals in the range of 0.38–0.001 μg/L, except for furosemide (max conc. 0.605 μg/L), paracetamol (max conc. 3.59 μg/L), metoprolol (never detected) and for atenolol (not analysed). In sediment samples, only paracetamol was not detected, while the others were generally found in the range of 0.4–0.02 μg/kgwwwith high concentrations for atenolol (max conc. 284μg/kgww) and furosemide (max conc. 98.4μg/kgww). The findings confirm also STPs as point sources of contamination. Despite of the much evidence for the adverse effects of pharmaceuticals in the aquatic environment, the observed low levels cannot be considered to pose a serious risk to human health; further studies are necessary for a comprehensive risk assessment.

Distribution of Nutrients in the Gulf of St. Lawrence

1979 ◽  
Vol 36 (2) ◽  
pp. 122-131 ◽  
Author(s):  
A. R. Coote ◽  
P. A. Yeats
Keyword(s):  
Surface Waters ◽  
General Pattern ◽  
Nutrient Concentrations ◽  
Physical Processes ◽  
Nutrient Distribution ◽  
General Increase ◽  
Dissolved Organics ◽  
Phosphate Nitrate ◽  
High Concentrations ◽  
Nitrate Distribution

The general pattern of nutrient distribution in the Gulf of St. Lawrence results from regeneration processes being superimposed on the physical processes of estuarine circulation within the Gulf. This leads to a general increase in nutrient concentration with depth and with distance into the Gulf from Cabot Strait. Nutrient concentrations in the Laurentian Channel are higher inside the Gulf than at equal or even greater depths in the Atlantic Ocean some distance outside Cabot Strait. Summer nutrient concentrations in the surface layer are generally low. However, during the winter when biological activity is low, quite high concentrations of the nutrients are found in the surface waters of the Gulf. A balance exists between inward and outward fluxes of all three nutrients through Cabot Strait in the winter. However, in the summer the influxes of both nitrate and silicate at Cabot Strait greatly exceed the outgoing fluxes. Losses of biogenic silica to the sediments may account for the silicate imbalance. Excess nitrate may be accounted for if ammonia or nitrogen bound with dissolved organics had been measured. Key words: nutrients, silicate, phosphate, nitrate, distribution, regeneration, transport, Gulf of St. Lawrence, Cabot Strait, Laurentian Channel

Osmoregulation of GPC:choline phosphodiesterase in MDCK cells: different effects of urea and NaCl

1995 ◽  
Vol 269 (1) ◽  
pp. C35-C41 ◽  
Author(s):  
E. D. Kwon ◽  
K. Zablocki ◽  
K. Y. Jung ◽  
E. M. Peters ◽  
A. Garcia-Perez ◽  
...  
Keyword(s):  
Enzymatic Degradation ◽  
Cell Function ◽  
Specific Activity ◽  
Mdck Cells ◽  
Absolute Rate ◽  
Madin Darby Canine Kidney ◽  
Organic Osmolyte ◽  
The Absolute ◽  
High Concentrations ◽  
Darby Canine Kidney

The organic osmolyte, glycerophosphocholine (GPC), accumulates in renal cells in response to high concentrations of either NaCl or urea, despite the very different effects of these solutes on cell function and volume. Together, high levels of these solutes increase GPC amount in Madin-Darby canine kidney cells by inhibiting its enzymatic degradation. The present study tests the effects of NaCl and urea, individually, on GPC accumulation and its degradation. A technique was developed to determine the absolute rate of GPC degradation by measuring the initial rate of disappearance of [3H]GPC (pulsed into the cells by hypotonic shock) and the specific activity of GPC in the cells. The mass of GPC in the cells was measured by another newly developed method, a sensitive chemiluminescent assay. We find that exposure to high NaCl or urea decreases the absolute rate of cellular GPC degradation by approximately one-half during the first 20.5 h. Reductions in GPC degradation are accompanied by commensurate decreases in the activity of GPC:choline phosphodiesterase (GPC:PDE; EC 3.1.4.2), an enzyme that catalyzes degradation of GPC. Activity of GPC:PDE falls > 50% in cells exposed for 2 h to high osmolality. Inhibition is sustained for 7 days with high urea alone. In contrast, with high NaCl alone, GPC:PDE activity reverts to control values by 7 days, by which time synthesis of GPC is increased, accounting for sustained GPC accumulation. Collectively, these data suggest that GPC accumulation in response to either high NaCl or urea occurs initially by inhibition of its degradation but that the effect of NaCl on degradation differs, in that it is transient, while that of urea is sustained.

X-ray structural studies of the entire extracellular region of the serine/threonine kinase PrkC from Staphylococcus aureus

2011 ◽  
Vol 435 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Alessia Ruggiero ◽  
Flavia Squeglia ◽  
Daniela Marasco ◽  
Roberta Marchetti ◽  
Antonio Molinaro ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Serine Threonine Kinase ◽  
X Ray ◽  
Threonine Kinase ◽  
Extracellular Milieu ◽  
Cellular Processes ◽  
Extracellular Region ◽  
High Concentrations ◽  
Growing Conditions ◽  
Adhesive Proteins

Bacterial serine/threonine kinases modulate a wide number of cellular processes. The serine/threonine kinase PrkC from the human pathogen Staphylococcus aureus was also shown to induce germination of Bacillus subtilis spores, in response to cell wall muropeptides. The presence of muropeptides in the bacterial extracellular milieu is a strong signal that the growing conditions are promising. In the present paper, we report the X-ray structure of the entire extracellular region of PrkC from S. aureus. This structure reveals that the extracellular region of PrkC, EC-PrkC, is a linear modular structure composed of three PASTA (penicillin binding-associated and serine/threonine kinase-associated) domains and an unpredicted C-terminal domain, which presents the typical features of adhesive proteins. Using several solution techniques, we also found that EC-PrkC shows no tendency to dimerize even in the presence of high concentrations of muropeptides. X-ray structural results obtained in the present study provide molecular clues into the mechanism of muropeptide-induced PrkC activation.

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