The changes in invertase activity and the content of sugars in the course of adaptation of potato plants to hypothermia

The pattern of changes in the activity of various forms of invertase (acid soluble, alkaline, and acid insoluble) and the content of sugars (glucose, fructose, and sucrose) in the course of plant adaptation to prolonged (6 days) hypothermia (5°C) was investigated in the leaves of potato plants (Solanum tuberosum L., cv. Desiree) produced in vitro. We used the wild-type plants as a control and transformed plants with carbohydrate metabolism modified by inserting the yeast gene for invertase (apoplastic enzyme). In the course of adaptation to hypothermia, the activity of acid invertase was shown to rise and the content of sucrose and glucose to increase in the leaves of both genotypes. The greatest activity of acid invertases by the third day of cold acclimation corresponded to the peak level of sugars; in transformed plants, these characteristics exceeded those in the control plants. The transformed plants were more cold resistant than the control plants as suggested by the lack of disturbance of ion permeability of their membranes. It was concluded that owing to accumulation of low-molecular carbohydrates in the course of cold acclimation caused by activation of acid invertase cold resistant plants better adapt to temperature drop.     

Phylogenetic in situ/ex situ analysis of a sulfur mat microbial community from a thermal sulfide spring in the north Caucasus

A phylogenetic in situ/ex situ analysis of a sulfur mat formed by colorless filamentous sulfur bacteria in a thermal sulfide spring (northern spur of the main Caucasian ridge) was carried out. Nine phylotypes were revealed in the mat. Thiothrix sp. and Sphaerotilus sp. were the dominant phylotypes (66.3% and 26.3%, respectively). The 16S rRNA gene nucleotide sequence of Sphaerotilus sp. phylotype from the clone library was identical to the sequences of the seven Sphaerotilus strains isolated from the same source. A very high degree of similarity of Sphaerotilus strains revealed by ERIC-PCR fingerprints indicated little or no population diversity of this species in the mat. Thiothrix phylotype from the clone library and two Thiothrix strains isolated from the same mat sample differed in one to three nucleotides of 16S rRNA genes; this is an indication of this organism’s population variability in the mat. 16S rRNA genes of the strains and clones of Thiothrix sp. exhibited the highest similarity (ca. 99%) with Thiothrix unzii; the strains and clones of Sphaerotilus had 99% similarity with the type species Sphaerotilus natans (the only species of this genus) and therefore can be assigned to this species. The minor seven components belong to the phylotypes from the Proteobacteria (3%), as well as the Chlorobia, Cyanobacteria, Clostridia, and Bacteroidetes phylogenetic groups, each of them constituting not more than 1%. Intracellular accumulation of elemental sulfur by Sphaerotilus similar to other filamentous sulfur bacteria was demonstrated for the first time (both in the population of the sulfur spring and in cultures with sulfide). Although mass growth of Sphaerotilus and Thiothrix is typical of bacterial populations of anthropogenic ecosystems (the activated sludge of treatment facilities), stable communities of these bacteria have not been previously found in the sulfur mats or “threads” of natural sulfide springs.     

Oxidative modification of blood plasma proteins in elderly people with vascular dementia

We examined the spontaneous and metal-ion-catalyzed oxidative modification plasma blood proteins in the group of healthy adults and elderly ones and patients with vascular dementia (mild and severe). We determined the spectrophotometric measurement of 2,4-dinitrophenylhydrazone derivatives formed by reactions with protein carbonyls. The level of metal-ion-catalyzed oxidation proteins in the aged patients both with and without dementia was high in comparison to the healthy adults. The patients with severe dementia showed lower amount of 2,4-dinitrophenylhydrazone deriviates. Low levels of metal-ion-catalysed protein oxidation strongly correlated with the degree of psychoorganic disturbances. The elderly persons with both and without dementia showed a high level of plasma nonenzymatic H2O2 scavenging in comparison with the healthy adult ones. We discovered an imbalance between enzymatic and nonenzymatic components of the antioxidant system. The latter indicates that the oxidative modification of brain tissue proteins probably plays an important role in aging and mental disorders.     

Lithoautotrophic growth of the freshwater colorless sulfur bacterium Beggiatoa "leptomitiformis" D-402

The freshwater colorless sulfur bacterium Beggiatoa "leptomitiformis" D-402 was shown to be capable of lithoautotrophic growth in a batch culture under microaerobic conditions at O2 concentrations in the medium of no higher than 0.5 mg/l. The cell yield was maximum at a dissolved oxygen concentration of 0.15 mg/l. A high activity level of key enzymes of the Calvin cycle and of enzymes involved in dissimilatory oxidation of thiosulfate was recorded in the cells. The high rate of CO2 assimilation (112-139 nmol/(min mg protein)) and the cell yield (12 mg dry cells/mmol thiosulfate oxidized), 91-92% of which was accounted for by CO2 carbon, were close to those typical of autotrophic bacteria. Thiosulfate was oxidized almost completely to sulfate, and the fraction of elemental sulfur in the final products did not exceed 0.2-1.7% of the thiosulfate sulfur. The cell membrane fraction contained cytochromes (b + o) and two cytochromes c with M(r) of 23 and 26 kDa; the soluble fraction contained cytochrome c with M(r) of 12 kDa.     

Oxidative Stress and Antioxidant Cell Protection Systems in the Microaerophilic Bacterium Spirillum winogradskii

The influence of oxygen availability during cultivation on the biosynthetic processes and enzymatic activities in the microaerophilic bacterium Spirillum winogradskii D-427 was studied, and the roles played by different systems of the defense against oxidation stress were determined. The metabolic adjustments caused by transition from microaerobic (2% O₂) aerobic conditions (21% O₂ of the gas phase) were found to slow down constructive metabolism and increase synthesis of exopolysaccharides as a means of external protection of cells from excess oxygen. This resulted in a twofold decline of the growth yield coefficient. Even though the low activity of catalase is compensated for by a multifold increase in the activities of other cytoplasmic enzymes that defend against toxic forms of O₂—peroxidase and enzymes of the redox system of glutathione (glutathione peroxidase and glutathione reductase)—massive lysis of cells starts in the midexponential phase and leads to culture death in the stationary phase because of H₂O₂ accumulation in the periplasm (up to 10 g/mg protein). The absence in cells of cytochrome-c-peroxidase, a periplasmic enzyme eliminating H₂O₂, was shown. It follows that the major cause of oxidative stress in cells is that active antioxidant defenses are located in the cytoplasm, whereas H₂O₂ accumulates in the periplasm due to the lack of cytochrome-c-peroxidase. The addition to the medium of thiosulfate promotes elimination of H₂O₂, stops cell lysis under aerobic conditions, lends stability to cultures, and results in a threefold increase in the growth yield.     

Role of malate dehydrogenase isoforms in the regulation of anabolic and catabolic processes in the colorless sulfur bacterium Beggiatoa leptomitiformis D-402

The functional role of tetrameric and dimeric isoforms of malate dehydrogenase in the carbon metabolism of the colorless sulfur bacterium Beggiatoa leptomitiformis, strain D-402, was studied. This strain can grow both lithotrophically and organotrophically. By using the inhibition analysis, the tetrameric isoenzyme was shown to operate in the glyoxylate cycle and the dimeric one was found to be involved in the TCA cycle. The dynamics of the dimeric isoenzyme conversion to the tetrameric isoform was found to be determined by the rate of thiosulfate oxidation. The regulation of the carbon metabolism in Beggiatoa leptomitiformis is supposed to be accomplished by means of structural and functional changes in the protein molecule of malate dehydrogenase.     

Development of a biosensor for electrochemical detection of tumor-associated proteins in blood plasma of cancer patients by aptamers

A molecular biosensor based on DNA aptamers (aptasensor) for the diagnosis of lung cancer in blood plasma samples was designed. To create the aptasensor, the aptamer 17_80, obtained in the study of postoperative material, was used. The affinity and binding selectivity of the aptamer 17_80 to the lung tumor tissue was confirmed on histological sections of postmortem samples of lung tissue. Using affinity enrichment and mass spectrometry, a possible target molecule of the aptamer 17_80, vimentin, was found.     

Anti-oxidant system of blood plasma]

Recent data available in literature and the author's data about the state of the antioxidant protection of the blood plasma have been generalized. The role of superoxide dismutase as the basic compound of the antioxidant system is discussed. The character of individual macromolecules (transferrin, ceruloplasmin, albumin) which have shown nonenzymatic specific antioxidant properties is presented. Possible mechanisms of biological activity of some antioxidants have been examined.