[Gas chromatographic determination of the makeup of the multicomponent gas mixtures in the vascula of the Warburg apparatus].
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Bacteriological Techniques↗
Biomedical subjects
Iu R Malashenko
Publications and source records attributed to Iu R Malashenko.
[Vital activity of methane-oxidizing bacteria after their filtration through coal pore structures].
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Coal↗
[The effect of organic substances on the assimilation of methane by obligate methylotrophs].
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Amino Acids↗
[Formation of the taxa of methane-oxidizing bacteria by numerical analysis methods].
Obligate methane oxidizing bacteria were classified within groups using numerical analysis and computer techniques. Employment of properties coinciding for all the species of the bacterial group under study was found to result in an insignificant (5--10%) change in the degree of similarity rather than in the redistribution of interrelationship; it had no effect on the formation of phenons. The Smirnov taxonomical analysis according to which the weight of a property is inversely proportional to its frequency has a number of advantages over other numerical methods where all the properties are assumed to be of equal value. Comparative evaluation of the data obtained by different methods which have been used by us to calculate the coefficients for coupled similarity of species (the coefficient of association, the coefficient of correlation, the index of distance, the coefficient of taxonomic ratio) shows that similar results are found in all the cases with respect to group division of the species belonging to the family Methylomonadaceae Leadbetter 1974. The species of methane oxidizing bacteria should be divided into the following genera: Methylosinus Whittenbury, Phillips a. Wilkinson 1970, Methylocystis Whittenbury, Phillips a. Wilkinson 1970, Methylococcus Foster a. Davis 1966, Methylomonas Leadbetter 1974.
Computers↗
[Sensitivity of soil bacteria isolated from the alienated zone around the Chernobyl Nuclear Power Plant to various stress factors].
Seventy strains of chemoorganotrophic bacteria isolated by our group in 1993-1994 from soil sampled in the zone around the Chernobyl Nuclear Power Plant (ChNPP) were studied with respect to their sensitivity to various stress factors damaging DNA. Bacillus subtilis, B. cereus (both spores and vegetative cells), Methylobacterium extorquens, M. mesophilicum, and unidentified pigmented bacteria were found to be the most resistant to ultraviolet (UV) radiation, exhibiting LD90 values of 40 to more than 211 J/m2. The same bacteria, as well as Bacillus polymyxa, were tolerant to hydrogen peroxide (lethal concentrations of H2O2 ranged from 0.3 to 1.0 M); i.e., UV-resistant strains were also tolerant to hydrogen peroxide and vice versa. Fluorescent pseudomonads were the most sensitive to both UV radiation and H2O2, showing LD90 from 6 to 18 J/m2 and a lethal concentration of H2O2 lower than 0.1 M. All of the soil samples collected in the alienated zone around the ChNPP, where the radioactivity of the soil had decreased from 1000 to 2 microCi/kg soil over the period from 1987 to 1995, contained not only resistant bacteria but also a small number of bacteria sensitive to UV radiation and H2O2.
Bacteria↗
[Ultraviolet irradiation of soil samples as a model of the effect of stress factors on bacterial diversity in soil ecosystem].
UV irradiation is proposed for use in studying the effect of radioactive irradiation, since radioresistant bacteria are, as a rule, resistant to UV, and the mechanisms of repair of cell damage induced by UV and ionizing radiation are similar. It was found that the total number of bacteria and the number of dominant species in soil samples exposed to UV radiation decreased, indicating the unfavorable effect of UV radiation on bacterial diversity in soil ecosystems. The percentage of cells of bacteria belonging to dominant species varied significantly depending on the intensity of UV irradiation. It can be inferred that long-term irradiation of soils must impair the stability of soil ecosystems, a phenomenon that was indeed observed in the zone around the Chernobyl Nuclear Power Plant. At the same time, the UV irradiation of soil samples made it possible to reveal minor species, primarily UV-resistant pigmented bacteria. UV irradiation can probably be used as a selective factor for the isolation of radioresistant species.
Bacteria↗
[Method of isolating pure cultures of mesophilic, thermotolerant and thermophilic methane-utilizing bacteria].
The paper describes a technique for isolation of pure cultures of various physiological groups (mesophilic, thermotolerant, and thermophilic) of methylotrophs bacteria. The technique is based on the application of solid media containing simultaneously two sources of carbon: elective for the accompanying microflora and elective for the obligate methylotrophs. If the culture to be studied is inoculated into such a medium, the following colonies will be found: (1) the initial culture; (2) pure cultures of the methylotrophs; and (3) the accompanying microflora. The paper presents a scheme for isolation of pure cultures of the methylotrophs, criteria for controlling their purity, recommendations for the composition of growth media which would not inhibit the growth of the obligate methylotrophs by organic substrates. The technique may also be used for the isolation of pure cultures of other bacteria (mycobacteria, lithotrophs, etc.) which are difficult to be separated from the accompanying microflora.
Bacteria↗
[Unique properties of highly radioresistant bacteria].
In connection with the Chernobyl Nuclear Power Plant (ChNPP) accident and the negative ecological after-effects for biota in this zone the interest has arisen to radioresistant bacteria, as to the most dynamic model of the given ecosystem, and to mechanisms which provide resistance of bacteria to ionizing radiation. The analysis of published data has shown that the radioresistant bacteria are not interrelated taxonomically and phylogenetically. The extreme radioresistant bacteria are represented by the Deinococcus species, which form a group phylogenetically close to the line Thermus-Meiothermus. Other radioresistant bacteria are the representatives of the genera Rubrobacter, Methylobacterium, Kocuria, Bacillus and some archebacteria. Data on natural habitats, of radioresistant bacteria are not numerous. In a number of cases it is difficult to distinguish their natural habitats, as they were isolated from the samples which were previously exposed to X-ray or gamma-irradiation, or from the ecosystems with the naturally raised radioactivity. To understand the strategy of survival of radioresistant bacteria, we briefly reviewed the mechanism of action of various species of radiation on cells and macromolecules; physiological signs of the cell damage caused by radiation; mechanisms eliminating (repairing) these damages. More details on mechanisms of the DNA repair in D. radiodurans are described. The extreme resistance of D. radiodurans to the DNA damaging factors is defined by 1) repair mechanisms which fundamentally differ from those in other procaryotes; 2) ability to increase the efficiency of a standard set of the DNA repairing proteins. Literary and own data on the effect of radiation on survival of various groups of bacteria in natural ecosystems are summarized. The ecological consequences of the ChNPP accident for soil bacteria in this region were estimated. The reduction of the number of soil bacteria and recession of microbial diversity under the effect of anthropogenic radiation was shown.
Bacteria↗
[Isolation and study of Acinetobacter sp. mutant strains defective in production of exopolysaccharides].
Nitrosoguanidine-induced mutants of Acinetobacter sp. defective in exopolysaccharide biosynthesis did not differ from the parent strain in distinguishing physiological and biochemical properties, such as requirements for growth factors, utilization of mono- and disaccharides, and resistance to antibiotics. The genetic relation of parent and mutant strains was shown by 16S rRNA PCR analysis. The comparative study of parent and mutant strains with respect to resistance to unfavorable environmental factors confirmed our hypothesis that Acinetobacter sp. exopolysaccharides perform protective functions. Hybridization experiments revealed the conjugal transfer of plasmid R68.45 from Pseudomonas putida BS228 (R68.45) to mutant but not to the parent Acinetobacter sp. strains. The role of the Acinetobacter sp. exopolysaccharides in providing the genetic stability of this bacterium is discussed.
Acinetobacter↗
[Processes of plant colonization by Methylobacterium strains and some bacterial properties ].
The pink-pigmented facultative methylotrophic bacteria (PPFMB) of the genus Methylobacterium are indespensible inhabitants of the plant phyllosphere. Using maize Zea mays as a model, the ways of plant colonization by PPFMB and some properties of the latter that might be beneficial to plants were studied. A marked strain, Methylobacterium mesophilicum APR-8 (pULB113), was generated to facilitate the detection of the methylotrophic bacteria inoculated into the soil or applied to the maize leaves. Colonization of maize leaves by M. mesophilicum APR-8 (pULB113) occurred only after the bacteria were applied onto the leaf surface. In this case, the number of PPFMB cells on inoculated leaves increased with plant growth. During seed germination, no colonization of maize leaves with M. mesophilicum cells occurred immediately from the soil inoculated with the marked strain. Thus, under natural conditions, colonization of plant leaves with PPFMB seems to occur via soil particle transfer to the leaves by air. PPFMB monocultures were not antagonistic to phytopathogenic bacteria. However, mixed cultures of epiphytic bacteria containing Methylobacterium mesophilicum or M. extorquens did exhibit an antagonistic effect against the phytopathogenic bacteria studied (Xanthomonas camprestris, Pseudomonas syringae, Erwinia carotovora, Clavibacter michiganense, and Agrobacterium tumifaciens). Neither epiphytic and soil strains of Methylobacterium extorquens, M. organophillum, M. mesophilicum, and M. fujisawaense catalyzed ice nucleation. Hence, they cause no frost injury to plants. Thus, the results indicate that the strains of the genus Methylobacterium can protect plants against adverse environmental factors.
Methylobacterium↗
[A two-stage technique for producing the microbial exopolysaccaride ethapolan with improved rheological properties].
A two-stage technique was proposed for cultivating producers of microbial exopolysaccharide ethapolan. The practical value of ethapolan is determined by its rheological properties. The use of a formaldehyde-supplemented medium at the second stage of cultivation improved the rheological properties of ethapolan without reducing its yield. This effect of formaldehyde was due to its binding to the exopolysaccharide, which altered the molecular-mass characteristics of the latter and protected the cells against the toxic action of formaldehyde. At all stages of its purification, ethapolan had improved rheological properties, suggesting that it was tightly bound to formaldehyde.
Acinetobacter↗
[Diauxotrophic properties of microorganisms assimilating C2--C4 hydrocarbons].
Diauxotrophic properties of bacteria assimilating gaseous hydrocarbons C2--C4 and other complex organic substances but not methane were studied. If the medium contained two substrates (hydrocarbon+carbohydrate), the non-growing cells of the strains did not display diauxotrophic properties. In the phase of exponential growth, oxygen-containing carbon sources and then gaseous hydrocarbons were assimilated, i.e. diauxia was observed. If a microbial association containing an obligate methylotroph and a facultative gas-assimilating culture was grown on a medium with a natural gas, the latter culture assimilated carbon-containing metabolites of the methylotroph and then, when their concentration decreased, gaseous hydrocarbons. The order in which complex organic substances (exometabolites of methylotrophs) and hydrocarbons C2--C4 were assimilated was determined by their concentration in the medium. In the course of growth of such a microbial association, the inhibiting effect of metabolites of methylotrophs on their growth decreased as well as the loss of methane being transformed by methylotrophs into exometabolites, and hydrocarbons C2--C4 were utilized.
Ethane↗
[Participation of microorganisms that oxidize gaseous hydrocarbons in the carbon cycle of the biosphere].
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Carbon↗
[Ethanol formation by methane-utilizing bacteria at ethane co-metabolism].
It was established, that EDTA (1.0 mM) and formamide (100 mM) are inhibitors of methanol dehydrogenase in Methylobacter luteus 12b, Methylomonas rubra 15sh and Methylococcus thermophilus 111p. The investigated strains co-metabolised ethane with the use of formate as the co-substrate. The application of formamide (or EDTA) as inhibitors of methanol dehydrogenase prevented from further transformation of ethanol and resulted in accumulation of extracellular ethanol. It was shown, that M. rubra 15sh accumulated extracellular ethanol under cultivation in a chemostate. The carried out researches have shown a regulation path of co-metabolism process of hydrocarbons by methane utilizing bacteria. Using the specific inhibitors of methanol dehydrogenase and a source of reducing agent (energy) for methane monooxygenase with the help of the cells of methane-oxidizing bacteria it is possible to obtain from ethane or other hydrocarbons the products of their monooxygenation--alcohols.
Ethane↗
[Peculiarities of ethanol metabolism in an Acinetobacter sp. mutant strain defective in exopolysaccharide synthesis].
Activities of the key enzymes of ethanol metabolism were assayed in ethanol-grown cells of an Acinetobacter sp. mutant strain unable to synthesize exopolysaccharides (EPS). The original EPS-producing strain could not be used for enzyme analysis because its cells could not to be separated from the extremely viscous EPS with a high molecular weight. In Acinetobacter sp., ethanol oxidation to acetaldehyde proved to be catalyzed by the NAD(+)-dependent alcohol dehydrogenase (EC 1.1.1.1.). Both NAD+ and NADP+ could be electron accepters in the acetaldehyde dehydrogenase reaction. Acetate is implicated in the Acinetobacter sp. metabolism via the reaction catalyzed by acetyl-CoA-synthetase (EC 6.2.1.1.). Isocitrate lyase (EC 4.1.3.1.) activity was also detected, indicating that the glyoxylate cycle is the anaplerotic mechanism that replenishes the pool of C4-dicarboxylic acids in Acinetobacter sp. cells. In ethanol metabolism by Acinetobacter sp., the reactions involving acetate are the bottleneck, as evidenced by the inhibitory effect of sodium ions on both acetate oxidation in the intact cells and on acetyl-CoA-synthetase activity in the cell-free extracts, as well as by the limitation of the C2-metabolism by coenzyme A. The results obtained may be helpful in developing a new biotechnological procedure for obtaining ethanol-derived exopolysaccharide ethapolan.
Acetaldehyde↗
[Structure of an acylated exopolysaccharide synthesized by Acinetobacter sp].
The complex preparation ethapolan synthesized by Acinetobacter sp. consists of neutral (minor component) and two acidic exopolysaccharides (EPS) one of which is acylated. On the basis of chemical modification of EPS, solvolysis with anhydrous hydrogen fluoride resulting in a penta- and octasaccharide fragments, Smith degradation, 1H- and 13C NMR analysis the following structure of the acylated polysaccharide repeating unit has been established (scheme): It is suggested that in the acylated EPS at least one glucose residue and the galactose residue are O-acylated.
Acinetobacter↗
[Thermophilic and thermotolerant bacteria that assimilate methane].
Microorganisms assimilating methane at temperatures above 40 degrees C were isolated from various natural sources: ooze, mud, waste water of coal pits. The bacteria are obligate methylotrophs and are represented by two groups: (a) thermotolerant, growing at 37 to 45 degrees C; and (b) thermophilic, growing at 50 to 62 degrees C. The selective factor used to isolate various physiological forms of methylotrophs is corresponding temperatures of growth which allow to isolate from the same substrate meso-, thermotolerant, and thermophilic forms. Morphological and physiological properties of the strains are described. The thermotolerant cultures of methylotrophs are similar to Methylobacter vinelandii, though differ from it by some characteristics. The thermophilic microorganisms should be classed as a separate species Methylococcus thermophilus.
Coal Mining↗
[Strategy of obtaining microbial exopolysaccharides possessing stable preset properties].
Basing on the development of approaches to the controlled regulation of synthesis of the complex polysaccharide preparation ethapolan (producer Acinetobacter sp.) the strategy of obtaining microbial exopolysaccharides (EPS) with stable composition and properties was determined. The strategy is based on the following principles of regulation of composition, physico-chemical properties and synthesis intensification of EPS: 1) to find out EPS functional groups determining their physico-chemical properties and factor providing synthesis of EPS with certain functional groups; 2) to study changes of EPS composition and properties during producer cultivation and to determine growth phase in which the synthesis of EPS possessing necessary properties occurs; 3) to investigate interrelation between EPS physico-chemical properties and their protective functions and to determine cultivation conditions necessary for development of EPS protective functions; 4) analysis of metabolic pathways of EPS synthesis, elucidation of "bottlenecks" in producer's metabolism and search for ways toward their elimination.
Acinetobacter↗