[The effect of organic substances on the assimilation of methane by obligate methylotrophs].
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Amino Acids↗
Biomedical subjects
V A Romanovskaia
Publications and source records attributed to V A Romanovskaia.
[The biology of bacteria that assimilate C1--C2 compounds and the biotechnology aspects of their use].
Main directions of the research work of the Department of Biology of Gas-Oxidizing Microorganisms are described in the paper. Fundamental studies concern ecology, selection, taxonomy, physiology, biochemistry, genetics of bacteria utilizing C1--C2 compounds, mathematical simulation of microbiological processes. Applied studies are devoted to development of scientific basis of biotechnologies for synthesis of important products (single cell protein, exopolysaccharides, food ingredients, biogas) from non-food substrates, search for the hydrocarbon deposits and protection of the environment.
Biotechnology↗
[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↗
[Nomenclature of obligate methylotrophs].
The nomenclature of obligate methylotrophs, i. e. bacteria using only reduced monocarbon compounds (methane, methanol, methylamines) as a carbon source, is dicussed. The chronology of naming taxons of methane oxidizing bacteria is presented and the rightfulness of their names is analyzed according to the rules of the International Codex of Bacterial Nomenclature. Such names as Methylomonas and others which are employed while describing various physiological groups of bacteria are used in the nomenclature of obligate methylotrophs, and this may be the source of errors. Therefore, only the genus of methane oxidizing bacteria should be referred to as Methylomonas whereas obligate methanol and methylamine assimilating bacteria should be classed as individual genera. The described species of methane oxidizing bacteria can be included into the genera Methylomonas, Methylococcus, Methylosinus, and Methylocystis. One should avoid such names as Methanomonas margaritae, Methanomonas immobilis, Pseudomonas methanica etc. since they do not possess the nomenclature status. All bacteria that depend obligatorily on the presence of reduced C1-compounds should be included into the family Methylomonadaceae. The taxonomy and nomenclature of facultative methylotrophs must be based on principles accepted for other organotrophic microorganisms as it has been suggested at the II International Symposium on the Growth of Microorganisms on C1-compounds (Pushchino, USSR, 1977).
Methylococcaceae↗
[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↗
[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↗
[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↗
[Search for methanotrophic producers of exopolysaccharides].
Bacteria that produce exopolysaccharides (EPS) and use methane as the only source of carbon were selected by studying a collection of methanotroph strains: Methylococcus capsulatus E 494, 874, and 3009; M. thermophilus 111p, 112p, and 119p; Methylobacter ucrainicus 159 and 161; M. luteus 57v and 12b; Methylobacter sp. 100; Methylomonas rubra 15 sh and SK-32; Methylosinus trichosporium OV3b, OV5b and 4e; M. sporium 5, 12, A20d, and 90v; and Methylocystis parvus OVVP. Mesophilic methanotroph strains with the ribulose monophosphate way of C1-compound assimilation synthesized EPS more actively than bacteria operating the serine cycle. The dynamics of EPS synthesis by methanotrophs during chemostat cultivation was studied.
Methane↗
[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↗
[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↗
[Stability of genetic markers in methane-oxidizing bacteria].
A number of Methylococcus thermophilus 111p clones have been obtained which have acquired resistance to tetracycline. The stability of maintenance of marker resistance in these clones and also in already designed Methylomonas rubra 15sh mutants has been investigated. Chromosomal markers resistance to antibiotics or formaldehyde were maintained in the marked strains Methylococcus thermophilus 111p and Methylomonas rubra 15sh after storage in nonselective conditions. The markers of resistance to antibiotics, which were coded by plasmids (pAS8-121 and pULB113), were not always preserved in Methylomonas rubra and Methylococcus thermophilus. The stability of maintenance of chromosomal markers in the investigated methane oxidizing bacteria testifies to the fact that they can be used in laboratory and industrial practice for testing the marked bacteria on selective media. The collection of the marked bacteria-mutants Methylomonas rubra 15sh and Methylococcus thermophilus 111p has been created. These strains stably support the marker resistance to various antibiotics or formaldehyde in unselective conditions.
Anti-Bacterial Agents↗
[Alternativity of methane assimilation pathways in obligate methylotrophs].
The activity of key enzymes involved in the primary pathways of methane assimilation and enzymes of the citrate cycle was determined in various obligate methylotrophs: mesophilic, thermotolerant, and thermophilic. The bacteria are characterized by the membrane ultrastructure of the I type, high activity of hexosephosphate synthase, NAD- and NADP-specific isocitrate dehydrogenase, and the absence of alpha-ketoglutarate dehydrogenase. The bacteria also displayed the activity of key enzymes of the serine cycle, hydroxypyruvate reductase, and serineglyoxylate aminotransferase. Therefore, both the ribulose monophosphate and serine pathways are involved in methane assimilation, and the division of methanotrophs into two groups, according to their metabolism, is tentative.
Aldehyde-Lyases↗
[The effect of gamma-radiation and desiccation on the viability of the soil bacteria isolated from the alienated zone around the Chernobyl Nuclear Power Plant].
Methylobacterium extorquens, M. mesophilicum, and Bacillus subtilis strains were found to be resistant to gamma-radiation, irrespective of whether they were isolated from the alienated zone around the Chernobyl Nuclear Power Plant or outside this zone. The LD90 of Methylobacterium and B. subtilis strains with respect to gamma-radiation was 2.0-3.4 and 3.7-4.4 kGy, respectively, whereas their LD99.99 values were 4.5-6.9 and more than 10 kGy, respectively. The high threshold levels of gamma-radiation for Methylobacterium and B. subtilis imply the efficient functioning of DNA repair systems in these bacteria. Unlike Bacillus polymyxa cells, the cells of M. extorquens, M. mesophilicum, and B. subtilis were also resistant to desiccation. Pseudomonas sp., Nocardia sp., and nocardioform actinomycetes were sensitive to both gamma-radiation and desiccation. Similar results were obtained when the bacteria studied were exposed to hydrogen peroxide and ultraviolet radiation. The results obtained indicate that the bacteria that are resistant to gamma-radiation are also resistant to desiccation, UV radiation, and hydrogen peroxide. The possibility of using simple laboratory tests (such as the determination of bacterial resistance to UV light and desiccation) for the evaluation of bacterial resistance to gamma-radiation is discussed.
Bacillus↗
[Thirty-five years of the Department of Biology of Gas-oxidizing Microorganisms of the D.K. Zabolotnyĭ Institute of Microbiology and Virology of the Academy of Sciences of Ukraine].
The basic trends of the department scientific activity are presented. The priority results of investigations of methaneoxidizing bacteria biology are given. The biothechnological development of the department (obtaining of products of microbial synthesis: protein, polysaccharides, antialcoholic and antinarcotic preparations) are considered in detail. Possible areas of their application are presented.
Academies and Institutes↗