Massive isolation of anamorphous ascomycete yeasts Candida oleophila from plant phyllosphere

Many years of research has confirmed a wide distribution of anamorphous ascomycete yeasts in the phyllosphere of diverse plants of the Moscow oblast. Based on the standard morphological and physiological criteria, on the results of restriction analysis of the 5.8S-ITS rDNA region, and on the sequencing of the D1D2 region of 26S rDNA, these yeasts were identified as Candida oleophila Montrocher. Previous isolation of this species has been rare, possibly due to its incorrect identification. This species, together with phytobiotic basidiomycete yeasts, was shown to be dominant in the yeast epiphytic communities on the surface parts of plants. The relative abundance of C. oleophila is highest on plant fruits and increases significantly by the end of the vegetation period. Wide occurrence of this yeast species on fruits and in the phyllosphere may be related to its ability to compete with rapidly growing phytopathogenic fungi.     

First isolation of the yeast Saccharomyces paradoxus in Western Siberia

Two ascomycetous yeast strains have been isolated near Novosibirsk from oak exudate. The strains have been identified as Saccharomyces paradoxus Bachinskaya based on the results of biochemical tests. The conspecificity of the isolates with S. paradoxus was confirmed by electrophoretic karyotyping and restriction analysis of the ITS region of its rDNA. This first isolation of S. paradoxus in Siberia provides evidence for the continuity of its natural habitats.     

Characterization of yeast groupings in the phyllosphere of Sphagnum mosses

Significant differences were revealed in the taxonomic structure of the epiphytic yeast communities formed on Sphagnum mosses and on the leaves of vascular plants. On mosses, low abundance of red yeasts was found (the most typical epiphytes on vascular plant leaves), along with a relatively high content and diversity of nonpigmented dimorphic basidiomycetes related to the order Leucosporidiales. The species composition of epiphytic yeasts from mosses is different from that of both forest and meadow grasses and of the parts of vascular plants submerged in the turf. The specific composition of the Sphagnum mosses yeast community is probably determined by the biochemical characteristics of this environment, rather than by the hydrothermal regime in the turf.     

Early manifestations of the effect of Salmonella endotoxin on the antioxidizing enzyme systems of the liver and intestines in the rat

A study was made of the effect of salmonellosis endotoxin (SE) on the activity of glutathione transferase (GT), glutathione peroxidase (GP-GTB and GP-H2O2), glutathione reductase (GR) and superoxide dismutase (SOD) in cytosols of the rat jejunal mucosa and liver. The activity of all the test enzymes of both the small intestine and liver was marked by drastic changes at the early stages of SE action. Thus, the activity of SOD and GP-H2O2 in the liver decreased after 30 min or 1 h of endotoxin action, respectively. In the jejunal mucosa, the activity of GP-H2O2 and SOD dropped after 4 h of SE action. GT in the jejunum remained unchanged, whereas in the liver, it was activated. The activity of GR and GP-GTB in the liver and jejunum was dissimilar. The causes and consequences of the abnormalities of the antioxidant enzymatic system and the role they play in the pathogenesis of salmonellosis intoxication are discussed.     

Intracellular distribution of creatine kinase isoenzymes in the brains and hearts of rats at different stages of postnatal development]

The total activity and range of the creatine kinase (CK) isozymes have been studied in the homogenate and subcellular fractions (nuclei, mitochondria, cytoplasm) of the rat brain and heart during postnatal ontogenesis. The total activity of CK in the brain and heart of newborn rats was found to be 4 and 2 times less, resp., than in those of adults. The age patterns were established in the activity of cytoplasmic (CK-1, CK-2 and CK-3) and mitochondrial (CK-4) isozymes. During the whole postnatal development the rat brain contains only one cytoplasmic isozyme, CK-1. In the heart of newborn rats, as compared with adults, the content of CK-1 and CK-2 is much higher and that of CK-3 lower. On the 12-15th day of life the range of the CK isozymes approaches that characteristic of adult animals. The activity of CK-4 was found in the brain on the 5-7th day of life and in the heart on 12-15th day. In the range of the CK isozymes in the adult brain the content of mitochondrial CK amounts to 19.3% and in the heart to 16.5%. The data obtained complement the literary ones suggesting the low level of energy-forming processes in the brain and heart cells at the early stages of the rat postnatal development.     

Prediction of the three-dimensional structure of aflatoxin of Aspergillus flavus by homology modelling

Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus spp. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. AFLR-Protein three-dimensional model was generated using Robetta server. The modeled AFLR-Protein was further optimization and validation using Rampage. In the simulations, we monitored the backbone atoms and the C-α-helix of the modeled protein. The low RMSD and the simulation time indicate that, as expected, the 3D structural model of AFLR-protein represents a stable folding conformation. This study paves the way for generating computer molecular models for proteins whose crystal structures are not available and which would aid in detailed molecular mechanism of inhibition of aflatoxin.     

Detection of new two-membrane structures in native mitochondria by the method of small-angle scattering of neutrons

The structure of mitochondrial cristas has been studied for the first time by the method of small-angle scattering of thermal neutrons. Experiments were performed on intact functioning rat liver mitochondria. Mitochondrial cristas are usually considered as folds of the internal membrane with arbitrary nonfixed intermembrane distances. It was shown that, under particular conditions, during low-amplitude swelling of mitochondria, cristas are transformed to bimembrane structures, with the distance between the central planes of membranes of 190 E. It was found that the formation of bimembrane structures and their structural parameters do not depend on the method of induction of swelling, by placing the mitochondria into a hypotonic medium or by the opening of nonspecific pores.     

Local coupling of respiration processes and phosphorylation in rat liver mitochondria

One variant of the model of the local coupling of phosphorylation and respiration in intact mitochondria was experimentally verified. The model is based on the following postulates: (1). Upon the functioning of H+ pumps, hydrogen ions bound to the outer membrane surface do not enter the aqueous phase but are utilized for ATP synthesis in the membrane supercomplex respiratory H+ pump--ATP synthetase. (2). During the functioning of H+ pumps, an appreciable part of the energy of oxidation reactions can be stored in the form of the thermodynamic (solvation) potential of H+ ions bound to the outer membrane surface. According to the model, the hydration of hydrogen ions during the transition from the outer face of the inner membrane to the aqueous phase should lead to a decrease in the efficiency of the system of the coupling of respiration and phosphorylation. The model takes into account the ability of the nonpermeating buffer to catalyze the detachment of hydrogen ions from the membrane surface to the aqueous phase and provide their complete solvation. A preparation of phosphorylating mitochondria with the covalently bound pH probe was obtained. This made it possible to register for the first time the presence of a local H+ gradient on the outer side of the inner mitochondrial membrane during the stable functioning of the oxidative phosphorylation system. It was shown on these mitochondrial preparations that a decrease in the outer local H+ gradient by the action of increased concentrations of buffer is accompanied by a significant decrease in the ADP/O parameter and a partial dissociation of oxidative phosphorylation. Conditions were determined under which increased concentrations of buffer in the incubation medium cause a partial dissociation and a decrease in the ADP/O value from 20% to twofold (depending on the quality of mitochondrial preparations). The results obtained are in full agreement with the predictions of the model.     

The structure and biogeochemical activity of the phototrophic communities from the Bol'sherechenskii alkaline hot spring

Microbial communities growing in the bed of the alkaline, sulfide hot spring Bol'sherechenskii (the Baikal rift area) were studied over many years (1986-2001). The effluent water temperature ranged from 72 to 74 degrees C, pH was from 9.25 to 9.8, and sulfide content was from 12 to 13.4 mg/ml. Simultaneous effects of several extreme factors restrict the spread of phototrophic microorganisms. Visible microbial fouling appears with a decrease in the temperature to 62 degrees C and in the sulfide content to 5.9 mg/l. Cyanobacteria predominated in all biological zones of the microbial mat. The filamentous cyanobacteria of the genus Phormidium are the major mat-forming organisms, whereas unicellular cyanobacteria and the filamentous green bacterium Chloroflexus aurantiacus are minor components of the phototrophic communities. No cyanobacteria of the species Mastigocladus laminosus, typical of neutral and subacid springs, were identified. Seventeen species of both anoxygenic phototrophic bacteria and cyanobacteria were isolated from the microbial mats, most of which exhibited optimum growth at 20 to 45 degrees C. The anoxygenic phototrophs were neutrophiles with pH optimum at about 7. The cyanobacteria were the most adapted to the alkaline conditions in the spring. Their optimum growth was observed at pH 8.5-9.0. As determined by the in situ radioisotope method, the optimal growth and decomposition rates were observed at 40-32 degrees C, which is 10 to 15 degrees C lower than the same parameter in the sulfide-deficient Octopus Spring (Yellowstone, United States). The maximum chlorophyll a concentration was 555 mg/m2 at 40 degrees C. Total rate of photosynthesis in the mats reached 1.3 g C/m2 per day. The maximum rate of dark fixation of carbon dioxide in the microbial mats was 0.806 g C/m2 per day. The maximum rate of sulfate reduction comprised 0.367 g S/m2 per day at 40 degrees C. The rate of methanogenesis did not exceed 1.188 micrograms C/m2 per day. The role of methanogenesis in the terminal decomposition of the organic matter was insignificant. Methane formation consumed 100 times less organic matter than sulfate reduction.