scholarly journals The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation

2007 ◽  
Vol 104 (18) ◽  
pp. 7705-7710 ◽  
Author(s):  
Brian Palenik ◽  
Jane Grimwood ◽  
Andrea Aerts ◽  
Pierre Rouzé ◽  
Asaf Salamov ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Surface Characteristics ◽  
Marine Phytoplankton ◽  
Major Protein ◽  
Ostreococcus Tauri ◽  
New Genes ◽  
Small Cell Size ◽  
Catalytically Active ◽  
Paradox Of Plankton ◽  
Ostreococcus Lucimarinus

The smallest known eukaryotes, at ≈1-μm diameter, are Ostreococcus tauri and related species of marine phytoplankton. The genome of Ostreococcus lucimarinus has been completed and compared with that of O. tauri. This comparison reveals surprising differences across orthologous chromosomes in the two species from highly syntenic chromosomes in most cases to chromosomes with almost no similarity. Species divergence in these phytoplankton is occurring through multiple mechanisms acting differently on different chromosomes and likely including acquisition of new genes through horizontal gene transfer. We speculate that this latter process may be involved in altering the cell-surface characteristics of each species. In addition, the genome of O. lucimarinus provides insights into the unique metal metabolism of these organisms, which are predicted to have a large number of selenocysteine-containing proteins. Selenoenzymes are more catalytically active than similar enzymes lacking selenium, and thus the cell may require less of that protein. As reported here, selenoenzymes, novel fusion proteins, and loss of some major protein families including ones associated with chromatin are likely important adaptations for achieving a small cell size.

scholarly journals Effect of Li2O Doping on the Surface and Catalytic Properties of the Fe2O3–NiO/Al2O3 System

1998 ◽  
Vol 16 (1) ◽  
pp. 21-32 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
N.M. Deraz
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Mixed Oxide ◽  
Active Sites ◽  
Catalytic Properties ◽  
Surface Characteristics ◽  
Appreciable Change ◽  
Surface Areas ◽  
Catalytically Active ◽  
Specific Surface Areas

Ferric–nickel/aluminium mixed oxide solids have the formula Fe2O3–0.42NiO/Al2O3 were treated with Li2O (0.75–3 mol%) and heated in air for 4 h at 500°C and 800°C, respectively. The effects of this treatment on the surface characteristics of these solids and their catalytic properties in relation to CO oxidation by O2 have been investigated. The results reveal that Li2O doping at 0.75 mol% concentration resulted in an increase of 24% and 18%, respectively, in the value of the specific surface areas, SBET, of the solids precalcined at 500°C and 800°C, while the addition of 3 mol% Li2O led to a slight decrease of ca. 10% in the SBET value of the same solids. In contrast, irrespective of whether the doping process involved solids precalcined at 500°C or 800°C, a significant decrease of 37% and 78%, respectively, was observed in the catalytic activity of these materials. This decrease in catalytic activity was not accompanied by any appreciable change in the magnitude of the activation energy for the catalytic reaction, i.e. Li2O doping brings about a decrease in the concentration of catalytically active sites without changing their energetic nature.

Catalytically Active Tetramodular 6-Deoxyerythonolide B Synthase Fusion Proteins

ChemBioChem ◽  
2003 ◽  
Vol 4 (11) ◽  
pp. 1225-1228 ◽  
Author(s):  
Corinne M. Squire ◽  
Rebecca J. M. Goss ◽  
Hui Hong ◽  
Peter F. Leadlay ◽  
James Staunton
Keyword(s):  
Fusion Proteins ◽  
Catalytically Active

scholarly journals Surface and Catalytic Properties of NiO and Fe2O3 Solids

1997 ◽  
Vol 15 (8) ◽  
pp. 593-607 ◽  
Author(s):  
A. Abd. El-Aal ◽  
A.M. Ghozza ◽  
G.A. El-Shobaky
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Active Sites ◽  
Pore Radius ◽  
Total Pore Volume ◽  
Surface Characteristics ◽  
Oxidation Of Co ◽  
Catalytic Activities ◽  
Catalytically Active ◽  
The Mean

The surface characteristics, viz., the specific surface area SBET, the total pore volume Vp and the mean pore radius r̄, of NiO and Fe2O3 were determined from N2 adsorption isotherms conducted at −196°C for the different adsorbents preheated in air at temperatures in the range 300–800°C. The catalytic activities exhibited in CO oxidation by O2 on the various solids were investigated at temperatures varying between 150°C and 400°C. The effect of heating the NiO and Fe2O3 solids in CO and O2 atmospheres at 175–275°C on their catalytic activities was also studied. The results showed that increasing the calcination temperature in the range 300–800°C resulted in a progressive decrease in the SBET value of NiO and Fe2O3. The computed values of the apparent activation energy for the sintering of the oxides were 71 and 92 kJ/mol, respectively. The sintering of NiO and Fe2O3 took place mainly via a particle adhesion mechanism. The catalytic activity of NiO decreased progressively on increasing its calcination temperature from 300°C to 800°C, due to a decrease in its SBET value and the progressive removal of excess O2 which was present as non-stoichiometric NiO. This treatment also decreased the catalytic activity of Fe2O3. The decrease was, however, more pronounced when the temperature increased from 300°C to 400°C which was a result of the crystallization of the ferric oxide into the α-Fe2O3 phase. An increase in the calcination temperature for both oxides from 300°C to 800°C did not modify the mechanism of oxidation of CO by O2 over the various solids but rather changed the concentration of catalytically active sites. Heating NiO and Fe2O3 in CO and O2 atmospheres at 175–275°C modified their catalytic activities, with Fe2O3 being influenced to a greater extent than NiO.

scholarly journals Genome Resolved Biogeography of Mamiellales

Genes ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 66
Author(s):  
Jade Leconte ◽  
L. Felipe Benites ◽  
Thomas Vannier ◽  
Patrick Wincker ◽  
Gwenael Piganeau ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Single Gene ◽  
Marine Phytoplankton ◽  
Taxonomic Resolution ◽  
Mating Types ◽  
Gene Markers ◽  
High Prevalence ◽  
Different Temperatures ◽  
Micromonas Pusilla ◽  
Ostreococcus Lucimarinus

Among marine phytoplankton, Mamiellales encompass several species from the genera Micromonas, Ostreococcus and Bathycoccus, which are important contributors to primary production. Previous studies based on single gene markers described their wide geographical distribution but led to discussion because of the uneven taxonomic resolution of the method. Here, we leverage genome sequences for six Mamiellales species, two from each genus Micromonas, Ostreococcus and Bathycoccus, to investigate their distribution across 133 stations sampled during the Tara Oceans expedition. Our study confirms the cosmopolitan distribution of Mamiellales and further suggests non-random distribution of species, with two triplets of co-occurring genomes associated with different temperatures: Ostreococcus lucimarinus, Bathycoccus prasinos and Micromonas pusilla were found in colder waters, whereas Ostreococcus spp. RCC809, Bathycoccus spp. TOSAG39-1 and Micromonas commoda were more abundant in warmer conditions. We also report the distribution of the two candidate mating-types of Ostreococcus for which the frequency of sexual reproduction was previously assumed to be very low. Indeed, both mating types were systematically detected together in agreement with either frequent sexual reproduction or the high prevalence of a diploid stage. Altogether, these analyses provide novel insights into Mamiellales’ biogeography and raise novel testable hypotheses about their life cycle and ecology.

scholarly journals Effect of γ-Irradiation on Some Surface and Catalytic Properties of Cr2O3/Al2O3 Solids Precalcined at 700°C

1998 ◽  
Vol 16 (3) ◽  
pp. 163-174 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
G.M. Mohamed
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Opposite Effect ◽  
Catalytic Properties ◽  
Surface Characteristics ◽  
Mechanical Mixing ◽  
Γ Irradiation ◽  
Untreated Sample ◽  
Surface Parameters ◽  
Catalytically Active

The effects of γ-irradiation (20–160 Mrad) on the surface characteristics (SBET, VP and r) and catalytic properties (in CO oxidation by O2) of chromia/ alumina solids have been investigated. The solids were prepared by mechanical mixing of CrO3 with finely powdered Al(OH)3, followed by drying at 120°C and calcination in air at 700°C. The amounts of chromia in the samples were 8.2 wt% and 27.1 wt%, respectively. The results obtained show that doses of 20–40 Mrad brought about a measurable increase in the surface characteristics (SBET, 46%; VP, 93%; r, 31%) of the sample containing 27.1 wt% Cr2O3 but doses above this limit had the opposite effect. However, the various surface parameters of the sample treated with 160 Mrad were still higher than those of the untreated sample. With the sample containing 8.2 wt% Cr2O3, varying the dosage of γ-irradiation in the range 20–160 Mrad led to smaller variations in the surface parameters. The catalytic activities of both types of sample were decreased by γ-irradiation, with the decrease being more pronounced for samples rich in chromia. Curves relating catalytic activity to dosage exhibited minima at 40 Mrad. The observed decrease in catalytic activity with γ-irradiation was attributed to a decrease in the concentration of catalytically active sites taking part in chemisorption and catalysis of the oxidation of CO by O2 without any change in their energetic nature.

scholarly journals Presence of a resident species aids invader evolution

2020 ◽  
Author(s):  
Josianne Lachapelle ◽  
Elvire Bestion ◽  
Eleanor E Jackson ◽  
C-Elisa Schaum
Keyword(s):  
Small Cell ◽  
Resident Species ◽  
Ostreococcus Tauri ◽  
Extinction Rates ◽  
Invading Species ◽  
Small Cell Size ◽  
Chlamydomonas Moewusii ◽  
Evolutionary Trajectories ◽  
Temperature Preferences ◽  
Ros Tolerance

AbstractPhytoplankton populations are intrinsically large and genetically variable, and interactions between species in these populations shape their physiological and evolutionary responses. Yet, evolutionary responses of microbial organisms in novel environments are investigated almost exclusively through the lens of species colonising new environments on their own, and invasion studies are often of short duration. Although exceptions exist, neither type of study usually measures ecologically relevant traits beyond growth rates. Here, we experimentally evolved populations of fresh- and seawater phytoplankton as monocultures (the green algae Chlamydomonas moewusii and Ostreococcus tauri, each colonising a novel, unoccupied salinity) and co-cultures (invading a novel salinity occupied by a resident species) for 200 generations. Colonisers and invaders differed in extinction risks, phenotypes (e.g. size, primary production rates) and strength of local adaptation: invaders had systematically lower extinction rates and broader salinity and temperature preferences than colonisers – regardless of the environment that the invader originated from. We emphasise that the presence of a locally adapted species has the potential to alter the invading species’ eco-evolutionary trajectories in a replicable way across environments of differing quality, and that the evolution of small cell size and high ROS tolerance may explain high invader fitness. To predict phytoplankton responses in a changing world, such interspecific relationships need to be accounted for.

The Nature of Rapidly Extracted Phycocyanin from the Blue-Green Alga Plectonema Boryanum

1971 ◽  
Vol 29 ◽  
pp. 366-367
Author(s):  
M. Kessel ◽  
R. MacColl
Keyword(s):  
Self Assembly ◽  
Analytical Ultracentrifugation ◽  
Uranyl Acetate ◽  
The Self ◽  
Major Protein ◽  
Subunit Structure ◽  
Blue Green Alga ◽  
Thin Sections ◽  
Blue Green Algae ◽  
Cacodylate Buffer

The major protein of the blue-green algae is the biliprotein, C-phycocyanin (Amax = 620 nm), which is presumed to exist in the cell in the form of distinct aggregates called phycobilisomes. The self-assembly of C-phycocyanin from monomer to hexamer has been extensively studied, but the proposed next step in the assembly of a phycobilisome, the formation of 19s subunits, is completely unknown. We have used electron microscopy and analytical ultracentrifugation in combination with a method for rapid and gentle extraction of phycocyanin to study its subunit structure and assembly.To establish the existence of phycobilisomes, cells of P. boryanum in the log phase of growth, growing at a light intensity of 200 foot candles, were fixed in 2% glutaraldehyde in 0.1M cacodylate buffer, pH 7.0, for 3 hours at 4°C. The cells were post-fixed in 1% OsO4 in the same buffer overnight. Material was stained for 1 hour in uranyl acetate (1%), dehydrated and embedded in araldite and examined in thin sections.

Reading the phosphorylation code: binding of the 14-3-3 protein to multivalent client phosphoproteins

2020 ◽  
Vol 477 (7) ◽  
pp. 1219-1225 ◽  
Author(s):  
Nikolai N. Sluchanko
Keyword(s):  
Protein Function ◽  
Intrinsically Disordered Protein ◽  
Structural Basis ◽  
Major Protein ◽  
Post Translational Modifications ◽  
Protein Protein Interaction ◽  
Intrinsically Disordered ◽  
Biochemical Journal ◽  
Multiple Binding ◽  
And Control

Many major protein–protein interaction networks are maintained by ‘hub’ proteins with multiple binding partners, where interactions are often facilitated by intrinsically disordered protein regions that undergo post-translational modifications, such as phosphorylation. Phosphorylation can directly affect protein function and control recognition by proteins that ‘read’ the phosphorylation code, re-wiring the interactome. The eukaryotic 14-3-3 proteins recognizing multiple phosphoproteins nicely exemplify these concepts. Although recent studies established the biochemical and structural basis for the interaction of the 14-3-3 dimers with several phosphorylated clients, understanding their assembly with partners phosphorylated at multiple sites represents a challenge. Suboptimal sequence context around the phosphorylated residue may reduce binding affinity, resulting in quantitative differences for distinct phosphorylation sites, making hierarchy and priority in their binding rather uncertain. Recently, Stevers et al. [Biochemical Journal (2017) 474: 1273–1287] undertook a remarkable attempt to untangle the mechanism of 14-3-3 dimer binding to leucine-rich repeat kinase 2 (LRRK2) that contains multiple candidate 14-3-3-binding sites and is mutated in Parkinson's disease. By using the protein-peptide binding approach, the authors systematically analyzed affinities for a set of LRRK2 phosphopeptides, alone or in combination, to a 14-3-3 protein and determined crystal structures for 14-3-3 complexes with selected phosphopeptides. This study addresses a long-standing question in the 14-3-3 biology, unearthing a range of important details that are relevant for understanding binding mechanisms of other polyvalent proteins.

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