Risk of Multiple Sclerosis: Analysis of Interactions between Variants of Nuclear and Mitochondrial Genomes

Molecular Biology - There is increasing evidence that the interaction of the mitochondrial and nuclear genomes substantially affects the risk of neurodegenerative diseases. The role of mitonuclear...     

A new subarctic strain of <Emphasis Type="Italic">Tetradesmus obliquus</Emphasis>—part I: identification and fatty acid profiling

We isolated a new subarctic strain Tetradesmus obliquus IPPAS S-2023 (Scenedesmaceae, Chlorophyceae) from rock baths in the White Sea. To verify its taxonomic assignment, internal transcribed spacer 2 (ITS2) of the strain was sequenced and its secondary structure was compared with predicted ITS2 secondary structures of Scenedesmaceae. The analysis of the ITS2 made it possible to assign the new strain IPPAS S-2023 to the species T. obliquus. The ultrastructural studies and energy-dispersive X-ray spectroscopy (EDX) analysis revealed a marked accumulation of vacuolar inclusions enriched in phosphorus and nitrogen (N) as well as cytoplasmiс oil bodies. Most of predicted properties of biodiesel derived from the fatty acids profile of the strain grown in the N-free medium complied with the requirements of European and American standards. The results suggest that the new subarctic strain T. obliquus IPPAS S-2023 is a promising candidate for nutrients biosequestration and for biodiesel production. In a companion paper, we assess its biomass production capability and suitability and demonstrated suitability of IPPAS S-2023 as a reference strain for studies on elevated CO₂ stress effects selection of carbon dioxide-tolerant microalgae by comparison with a CO₂-tolerant strain IPPAS S-2014.     

Variability of the MIR196A2 Gene as a Risk Factor in Primary-Progressive Multiple Sclerosis Development

Molecular Biology - Multiple sclerosis is a chronic disease of the central nervous system, combining in its pathogenesis both autoimmune and neurodegenerative components, and is characterized by a...     

Changes in the cell ultrastructure of the haloalkaliphilic endoevaporite cyanobacterium <Emphasis Type="Italic">‘Euhalothece natronophila’</Emphasis> during fossilization

The ultrastructure of the haloalkaliphilic endoevaporite cyanobacterium ‘Euhalothece natronophila’ Z-M001 from the soda Lake Magadi was investigated during the initial stages of fossilization in a model experimental system. The cyanobacterium was cultivated in concentrated carbonate solution supplemented with calcium chloride. It was revealed that the amorphous CaCO₃ formed under these conditions could interact with the cell wall during the first stages of ‘E. natronophila’ calcification. Evidence is presented that the surface layer of the ‘E. natronophila’ envelope, presumably containing polysaccharide and/or (glyco)protein components, can be involved in the adsorption and subsequent crystallization of CaCO₃ with the formation of a massive “shell” embedding the morphologically intact cells. It was established that the ultrastructure of the cell wall and the intrathylakoid space changed during CaCO₃ mineralization. During the later fossilization stages, cells covered by the calcium-containing “shell” were apparently mummified, and mostly retained their original shape. The encapsulation of cyanobacteria in the trona globule was characterized by a different pattern. It probably involved tight binding of the growing crystal to the glycocalyx components that are anchored in the outer membrane. This may result in its detachment from the underlying peptidoglycan layer. The peptidoglycan was retained, and the protoplasts were ultrastructurally similar to the intact ones. Cyanobacteria incorporated in large trona crystals underwent degradation, deformation, and destruction. This accounts for the fact that massive trona deposits of Lake Magadi lack cyanobacterial fossils that are abundant in calcium-containing strata.     

A new subarctic strain of <Emphasis Type="Italic">Tetradesmus obliquus</Emphasis>. Part II: comparative studies of CO<Subscript>2</Subscript>-stress tolerance

A huge interest in CO₂-tolerant microalgae is fueled by development of CO₂-biomitigation methods based on intensive cultivation of microalgae. Still, the mechanisms of CO₂-tolerance are scarcely investigated. Previously, we described a symbiotic Desmodesmus sp. IPPAS S-2014 from a White Sea hydroid tolerant to extremely high (20–100%) CO₂ levels. In the present work, we compared its ultrastructural and physiological responses to those of a novel free-living White Sea strain of Tetradesmus obliquus IPPAS S-2023 characterized in the companion paper. The strain S-2023 is closely related to Desmodesmus sp. IPPAS S-2014 but lacks its tolerance to extremely high CO₂ (it is unable to survive at 100% CO₂ and exhibits a reduced-growth phenotype when sparged with 20% CO₂: air mixture). We compared the responses of the cell organization and photosynthetic activity to 20% CO₂ in the tolerant and the intolerant White Sea chlorophytes using chlorophyll fluorescence measurements and ultrastructural analysis (transmission electron microscopy). The features peculiar to the CO₂-intolerant chlorophyte include (i) inability to maintain pH homeostasis, (ii) a steady decline in the photosynthetic activity of the cells, (iii) a reduction of the photosynthetic membranes, and (iv) delayed accumulation of starch (starch grains) and its subsequent conversion to reserve lipids (oil bodies). Nitrogen starvation enhances the effects of high-CO₂ stress in the CO₂-intolerant microalga. The results of this work are discussed in the context of selection of tolerant algal strains for CO₂ biomitigation applications.     

Destruction of Pigments and Ultrastructural Changes in Cyanobacteria during Photodamage

Sequential stages of pigment degradation and ultrastructural changes were examined in cyanobacteria Anabaena variabilis ATCC 29413, Synechococcus sp. PCC 6301 (Anacystis nidulans) and S. elongatus B-267 during irradiation of cell suspensions with high-intensity light. Early manifestations of photooxidative destruction were evident as profound changes in ultrastructure of thylakoids; in A. variabilis these changes appeared even before bleaching of pigments. Concomitant to these alterations, the cytoplasmic matrix turned homogenous and the nucleoid was subject to degradation, while ultrastructural changes of cytoplasmic membrane and cell walls became evident in some species. In A. variabilis these changes were related to a subsequent autolysis of cells. Synechococcus strains demonstrated comparatively high resistance to irradiation. The experimental data were compared with previously described behavior of the same species of cyanobacteria cultured under photooxidative conditions. This comparison revealed principal similarity and species-specific features in the destructive changes of thylakoids and other cell components of cyanobacterial cells.     

Atypical Cell Forms Overproducing Extracellular Substances in Populations of Cycad Cyanobionts

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycas circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. The cyanobiont microcolonies grown in the intercellular space of the cyanobacterial zone of cortical parenchyma in the cycad coralloid roots contained two specific forms of vegetative cells with a reduced cell wall, namely, protoplasts and spheroplasts. The protoplasts and spheroplasts exhibited ultrastructural properties indicating the overproduction of two extracellular substances, one of which resembled the mucilage polysaccharides and the other was protein-like. The substances were likely to be synthesized intracellularly and then be excreted with the aid of surface vesicles or by ruptures in the cytoplasmic membrane to form, respectively, a mucilagious extracellular matrix and an additional electron-opaque envelope around the cell. At the late developmental stages, the excretion of these substances was accompanied by degradative changes in the cells, leading eventually to cell death. The physiological role of these specific cell forms and the factors that induce their development and death in the cell populations of cyanobionts are discussed.