Search

Выявлены основные закономерности изотермического течения топлива и окислителя в микрофакельном горелочном устройстве с односторонней подачей топлива. Получены данные компьютерного моделирования с использованием подхода DES (Detached Eddy Simulation), представляющего собой комбинацию моделей RANS (Reynolds Averaged Navier-Stokes) и LES (Large Eddy Simulation) в разных областях пространства. Установлены эффекты влияния длины закрылка, расположенного на торцевой поверхности стабилизаторов пламени, на различные характеристики течения. Показано, что наличие закрылков приводит к существенному изменению вихревой структуры в следе за стабилизаторами. Оценено влияние длины закрылков на такие параметры течения, как протяженность зоны обратных токов в закормовой области стабилизаторов пламени, уровень среднеквадратичных пульсаций скорости в данных зонах и пр. Установлено, что с увеличением длины закрылков существенно возрастает протяженность зоны обратных токов за стабилизатором. Выявлено также, что чем короче закрылки, тем больше превышает их длину протяженность зоны обратных токов. Выполнен анализ пространственного распределения пульсаций скорости в рассматриваемом горелочном устройстве при наличии и отсутствии закрылков на торцевых поверхностях стабилизаторов пламени. Показано, что наиболее высокий уровень данных пульсаций наблюдается вблизи границы зоны обратных токов, удаленной от торца стабилизатора. Установлено, что уровень среднеквадратичных пульсаций скорости является наиболее высоким в условиях отсутствия закрылка и снижается при увеличении его длины.

The aim of this study was to determine homeostasis quantitative parameters (maximum permissible concentrations of xenobiotic and types of cell response) of microbial communities from cave clays influenced by p-nitrochlorobenzene. It was determined the ability of cave bacteria to transform xenobiotic. General bacteriological methods were used as well as gas chromatography-mass-spectric method. Chemoorganotrophic karst caves microbial communities isolated from Mushkarova Yama (Podolia, Ukraine) and Kuybushevskaya (Western Caucasus, Abkhazia) were highly resistant to p-nitrochlorobenzene. For Mushkarova Yama representative strain Rhodococcus erythropolis P3 the influence of p-nitrochlorobenzene (in concentration range 50–300 mg/l) on physiological parameters of bacterial cells was shown. The efficiency of p-nitrochlorobenzene degradation was proportional to the decreasing of redox potential. Thus, cave microorganisms could potentially be used to create new environmentally friendly biotechnologies, for example enterprises for wastewater treatment from nitrochloraromatic compounds.

The biochemical mechanisms of resistance to persistent organic xenobiotic p-nitrochlorobenzene (NCB) of bacterial strains isolated from two cave clays ecosystems – Mushkarova Yama (Podolia, Ukraine) and Kuybyshevskaya (Western Caucasus, Abkhazia) have been established. It has been determined that chemoorganotrophic karst caves strains could interact with NCB and transform it reducing the nitro group with formation of p-chloroaniline (ClA) followed by further destruction of NCB aromatic ring. This explained high resistance of caves strains to NCB. The studied strains could potentially be used in wastewater treatment from nitrochloraromatic compounds.

To determine the studied bacteria resistance quantitative parameters of extreme factors such as toxic metals (Cu2+), organic xenobiotics (p-nitrochlorobenzene) and UV-irradiation were the aim of the research. Six strains of nitrogen-fixing bacteria isolated from clays of two caverns Mushkarova Yama (Podolia, Ukraine) and Kuybyshevskaya (Western Caucasus, Abkhazia) and Azotobacter vinelandii УКМ В-6017 as a reference strain have been tested. For this purpose the maximum permissible concentration of Cu2+ and p-nitrochlorobenzene in the concentration gradient and lethal doses of UV by the survival caverns have been determined. Maximum permissible concentrations for strains were as 10 ppm Cu2+, 70–120 ppm of p-nitrochlorobenzene. The maximum doses of UV-irradiation varied in the range of 55–85 J/m2 (LD99.99). It is shown that three classes of extreme factors resistance parameters of karst caverns strains are similar to the strain of terrestrial soil ecosystems. The most active studied strains reduce the concentration of p-nitrochlorobenzene in the medium in 13 times. The ability of nitrogen-fixing bacteria to degrade p-nitrochlorobenzene could be used in creation new environmental biotechnology for industrial wastewater treatment from nitrochloroaromatic xenobiotics. Isolated strains could be used as destructors for soils bioremediation in agrobiotechnologies and to optimize plants nitrogen nutrition in terrestrial ecosystems.

The paper presents the final results of a five-year research (2011-2015) conducted at the Extremophilic Microorganism Biology Department. Extremotolerant microorganisms were isolated from phytocenoses and soils of West Antarctic; subtropical soils (Israel), karst caves and soils of temperate regions (Ukraine, Bulgaria), silt of hypersaline lakes of Crimea (Ukraine) and the Dead Sea (Israel), highland areas of Andes (Ecuador). 10% of them were resistant to toxic metals, 1-chloro-4-nitrobenzene, UV radiation, high salinity, as well as to low and high temperatures. A method of thermodynamic prognosis of microbial interaction with various toxic compounds was developed, providing a theoretical background for designing new environmental biotechnologies. It enabled to determine the conditions for microbial metabolism regulation that provide for complete degradation of synthetic organic compounds and food wastes as well as for production of energy carriers (H2, CH4, ethanol, solid fuel). The specified approach resulted an isolation of a number of strains that were resistant to the most toxic metals (Hg2+, Cu2+, Ni2+, Fe3+, Fe2+, CrO42-) and performed a variety of interactions with metal compounds including mobilization and immobilization, dissolving and sedimentation. Biodiversity of microorganisms in West Antarctica was studied by means of standard microbiological methods as along with phylogenetic and metagenomic analysis. Pyrosequencing of 16S rDNA amplicons of microbial communities in the studied samples revealed representatives of 20 bacterial phyla. Microbiological methods identified cultivable representatives of four phyla (Actinobacteria, Firmicutes, Proteobacteria, Bacteroidetes), which included 25 species. The paper presents the results of taxonomic and/or biotechnology studies of specialized groups of extremophiles: ironreducing bacteria, hydrogen-producing bacteria and obligate methane-oxidizing bacteria. [ABSTRACT FROM AUTHOR]

Purpose: To determine resistance to dehydratation of bacteria resistant to UV irradiation., Methods: Objects of research - extremophilic bacteria (from Antarctic islands and hypersaline reservoirs of Israel and Crimea). Dehydratation of bacteria was carried out in sealed desiccator; the exposure without access of moisture was 5 weeks, temperature - 22 - 25 °C, humidity - 1 - 4 %. UV irradiation of bacteria was carried out by lamp BUF 15 (A = 254 nm) in the range of 40 - 2400 J/m(2). After cultivation irradiated and not irradiated strains (before and after UV irradiation and before and after drying) we determined the number of cells., Results: The extremely resistant to dehydratation (Firmicutes) and extremely sensitive to dehydratation (Proteobacteria, Bacteroidetes) strains was found among the studied bacteria. Most strains of bacteria that were resistant to dehydratation were also resistant to UV irradiation. Survival after dehydratation in these bacteria was 6.32 - 55.26 % and UV LD99.99 240-600 J/m(2). Instead, representatives of Proteobacteria were extremely sensitive to these extreme factors: the cell survival was 0 - 1.6 % after dehydratation and UV LD99.99 80 - 180 J/m(2)., Conclusions: The results support the hypothesis that between bacteria resistance to electromagnetic radiation (UV) and their resistance to dehydratation there is a correlation.

In this paper it was given the effect of p-nitrochlorobenzene (NCB) on the homeostasis quantitative parameters of cave clays microbial communities from Western Ukraine and Abkhazia (Mushkarova Yama, Kuybushevskaya) and soils of Ecuador tropical ecosystems. For these microbial communities were determined maximum permissible concentrations and types of responses on xenobiotic. Microbial communities of Mushkarova Yama cave clays and rainforest soils of Ecuador were characterized by the first type of response. Microbial communities of Kuybushevskaya clays and mountain jungles of Ecuador were characterized by the second type of response. Maximum permissible concentration of NCB for Mushkarova Yama was 200 mg/l, for the other studied microbial communities--300 mg/l. It was shown, that microbial communities were not only highly resistant to NCB but also interacted with it by destroying this xenobiotic and decreasing its concentration in 4 times.

34 strains of aerobic chemoorganotrophic microorganisms were isolated from 23 soil and plant samples selected from highland biotopes of Ecuador-Andes massif (Papallacta, 4020 m), ash at the foot of the volcano Tungurahua, mountainous jungle (La Favorita, 1600 m), as well as in humid tropic botanical garden (state Puyo, 950 m). In mountain jungle samples the high number of bacteria--10(5)-10(7) CFU/g of sample were represented by 2-5 morphotypes. In highland (4020 m) samples the bacterial counts made from 10(2) to 10(7) CFU/g of sample. The current study describes resistance of isolated strains to high salinity, UV radiation and toxic metal ions. The majority of isolated strains were halotolerant. Isolates from volcanic ash showed high resistance level to UV radiation--LD99,99 made 1000-1440 J/m2; resistance level for isolates from the soil of Puyo Botanical Garden and isolates from rock lichen (Papallacta) LD99,99 made 1160 and 800 J/m2 respectively. Strains isolated from mountain jungle (La Favorita) showed lower UV-resistance. In highland biotopes of Ecuador occurred bacteria resistant to toxic metal ions. The highest resistance to Hg2+ was shown by isolate of lichen from mountain jungle, the maximal growth concentration was 0.025 g/L; to Cr(VI)--by isolate from lichen rock massif--3,0 g/L. Correlation between metal-resistance, halotolerace and UV resistance for studied strains was not detected, probably because of different microbial cell damage/repair mechanisms under the action of these factors.

Five strains of the black yeast similar to Exophiala nigra (Nadsoniela nigra), which we have isolated from the Antarctic biotopes, are studied. At cultivation in a periodic operation the maximum level of absolutely dry biomass in five tested strains constituted 3.2-7.8 g/l of medium, melanin pigment yield being 6-9% of absolutely dry mass of cells. Two highly productive strains have been selected. Pigments of the studied black yeast are water-insoluble, however dissolve in alkali and concentrated acids. The maximum absorption of the yeast pigments was in the range of 220 nm. The above-stated properties of pigments of the investigated yeast correspond to the description of melanin fractions of Nadsoniela nigra and some microscopic mushrooms. The water-soluble melanin-pigments have been obtained after the dialysis of alkaline solution of the pigment. UV-spectra and visible absorption spectra of water solution of melanin-pigments are almost identical to those of initial alkaline solutions. It is shown that the studied yeast are resistant to high concentrations of toxic metals (Hg2+, Cu2+, Co2+, Cr(VI) and Ni2+), and introduction of Co2+ into the cultivation medium leads to the increase of pigments synthesis.

Resistance to toxic metals ( Hg2+, Cu2+, Ni2+, Co2+, Cr(VI)) of bacteria isolated from rock lichen samples of vertical cliffs located on the biogeographic polygon of Ukrainian Antarctic Station Akademik Vernadsky (island Galindez) is studied. Among the Antarctic rock microorganisms isolated on nonselective medium (without toxic metals), bacteria able to grow at toxic metal concentrations lethal for the majority of microorganisms (Hg2+, Cu2+, Ni2+, Co2+, Cr(VI)) are found out. The studied bacteria are most resistant to Cr(VI) possessing oxidative properties in concentration range 1.25-20.0 g/l depending on the strain. Maximal metal concentrations, at which the growth of bacteria was possible, was: Ni2+ to toxic metals - 2.0 g/l, Co(2+) - 0.1 g/l. In the presence of metal ions possessing both replacing and oxidative properties the strains grew in a concentration range: Hg(2+) - 0.005-0.05 g/l, Cu(2+) - 0.1-1.25 g/l. The highest toxic effect was shown for mercury ions. One of the isolated Antarctic strains which was superresistant to high toxic metal concentrations (g/l): Cr(VI) - 20.0, Ni(2+) - 2.0, Cu(2+) - 1.25, Co(2+) - 0.1, Hg(2+) - 0.05. Thus, for the Antarctic bacteria isolated from rock damaging or bactericidal toxic metal concentrations are by 2-3 orders higher than for the majority of microorganisms.

The paper deals with the samples of microorganisms isolated from biofilms of encrustation of 11 stationary points of monitoring on the vertical rock of biogeographical testing ground (island Galindez, Antarctic Region). They are presented by morphologically various forms of bacteria (n x 10(7) cells in 1g of sample), yeast (n x 10(5)) and fungi (n x 10(4)-10(6)). Threshold and lethal UV dozes for isolated monocultures of the Antarctic microorganisms are determined. The threshold doze of UV radiation which is a measure of ability of a cell to reparation of DNA damages for bacteria was 40-70 J/m2. The lethal UV doze (LD99.99) for bacteria varied within the limits of 200-480 J/m2, for yeast of 700-1200 J/m2. Both pigmented and not pigmented bacteria were resistant to UV radiation. As a rule, Gram-positive bacteria were more resistant to UV than Gram-negative ones. It is shown, that resistance of investigated Antarctic rocky microorganisms to UV radiation is their genetically stable characteristic.

To determine a possibility of application of phylogenetic criteria for estimating the taxa rank, the intra- and interspecies, as well as intergeneric relatedness of methanotrophs on the basis of 16S rRNA gene sequences was estimated. We used sequences of 16S rRNA genes of the studied isolates of obligate methanotrophs which have been deposited in UCM (Ukrainian Collection of Microorganisms), and of type strains of other obligate methanotrophs species (from GenBank database). It is shown, that the levels of interspecies and intergeneric relatedness in different families of methanotrophs are not identical, and therefore they can be used for differentiation of taxa only within one family. The carried out analysis has shown, that it is necessary to reconsider taxonomic position: (1) of two phenotypically similar species of Methylomonas (M. aurantiaca and M. fodinarum), similarity of 16S rRNA genes which is 99.4%, similarity of their total DNA--up to 80% that rather testifies to strain differences, than to species differences; (2) of species Methylomicrobium agile and M album which are phylogenetically more related to genus Methylobacter (97% of affinity), than Methylomicrobium (94% of affinity); (3) of genera of the family Beijerinckiaceae (Methylocella and Methylocapsa), and also genera of the family Methylocystaceae (Methylosinus and Methylocystis), whereas high level of relatedness (97% and more) of these bacteria with other methanotrophic genera (within one family) practically corresponds to a range of relatedness of species (within some genera) in the family Methylococcaceae. When determining phylogenetic criteria which can characterize the ranks of taxa, it was revealed, that the levels of interspecies relatedness of methanotrophic genera of the families Methylocystaceae and Beijerinckiaceae (97.8-99.1% and 97.8%, accordingly) considerably exceed the level of genera formation in the family Methylococcaceae (94.0-98.2%) and, moreover, approach the value of intraspecies relatedness of the family Methylococcaceae (97.5-99.3%). Coefficients of intraspecies relatedness of methanotrophs of the families Methylocystaceae and Beijerinckiaceae are sometimes equal to interspecies relatedness. Hence, taxa of various rank can have the identical level of genes divergence. Thus, methanotrophic taxons of the families Methylocystaceae and Beijerinckiaceae have not demonstrated precise phylogenetic criteria which could correspond both to the species rank, or the genus rank. At the same time, the criteria, being adequate to the rank of certain taxa, are revealed in methanotrophs of the family Methylococcaceae. The level of genotypic relatedness of strains of the same species is in the range of 97.5-99.3%, species of the same genus--94-98%, the highest levels of relatedness between genera of this family are 90-96%.

Technologically promising microbe association, consisting of aerobic and anaerobic sporulating bacteria has been isolated. The association synthesizes molecular hydrogen during fermentation of potato and starch. The association was isolated from soil, pasteurized on the boiling water bath. The association destroys potato during 5-7 days with a decrease of mass up to 17.4 times and synthesizes gas consisting of 60% of H2.

Microbiological analysis has been made of 120 samples from biotopes of the western coast of the Antarctic peninsula (Rasmussen cope, Tuxen cope, Waugh mountain), Argentine archipelago islands (Galindez, Skua, Corner, Barchans, Irizar, Uruguay, Cluls, Three Little Pigs, King-George), as well as neighbouring islands (Petermann--on the north, a group of Jalour islands--on the east, Berthelot--on the south-east); and more remote islands (Darboux, Lippmann, Booth). It was found out that the total number of chemoorganotrophic aerobic microorganisms was 10(6) - 10(8) cells/g of soil, that was by 2-3 orders lower than in the regions with temperate climate. One can observe a tendency of decreasing the quantity of chemoorganotrophic microorganisms in the Antartic biotopes (cells/g of a sample) in the following order: soil (1 x 10(7) - 8 x 10(8)), underground part of moss (1 x 10(6) - 5 x 10(7)), grass Deschampsia antarctica (10(6) - 10(8), slit of fresh-water reservoir (10(5) - 10(7)), ground part of moss (10(3) - 10(6)), lichens (10(3) - 10(6)). Representatives of several phylogenetic lines: Proteobacteria (genera Pseudomonas, Methylobacterium, Enterobacter), Firmicutes (genera Bacillus, Staphylococcus), Actinobacteria (genera Brevibacterium, Actinomyces, Streptomyces) have been found in the Antarctic samples. As a rule, genera of bacteria found in the Antarctic Region are widely distributed in different regions of the Earth with temperate climate. Microorganisms similar to the species Exophiala nigra (Issatsch.) Haats et de Hoog 1999, which was first detected 100 years ago by Academician B.L. Isachenko in the Arctic region water, were also isolated from biofilms on vertical rocks of the Galindez Island as well as from the soil of the Irizar Island.

Methylotrophs distribution has been studied in the terrestrial biotopes (moss, lichen, grass, soil, sludge of lakes) on the islands of Galindez, Barkhans, Irizar, Uruguay, Jalour, Petermann, Berthelot, Cruls, King George, Corner, Skua located in the Pacific sector of the Antarctic Region, as well as in analogous biotopes on the western shore of the Antarctic peninsula Basing on a complex of diagnosis features the isolated pink-pigmented strains, which facultatively use methanol and realize the serine cycle of assimilation of one-carbon compounds, are attributed to Methylobacterium genus. Methylobacterium strains occur more often in mosses, grass Deschampsia antarctica and lichens, than in the soil and lake sludge. Some regions ofAntarctica are comparable by the number of Methylobacterium cells with the same in the regions with moderate climate. An analysis of gene sequences 16S rRNA of the Antarctic methylobacteria with those of GenBank has shown a high extent of similarity with Methylobacterium extorquens (99.4-99.7%). Notwithstanding that the strains of Methylobacterium are resistant to the broad range of extreme factors (gamma-irradiation, UV-irradiation, dehydration), the Antarctic and collection strains of the genus were sensitive to the ions of such heavy metals as Cu, Hg, Cd, Cr (10 mg/l).

Sequence-analysis of genes 16S rRNA has demonstrated the high-level relationship (99%) of the strains Methylobacter ucrainicus UCM B-3159, and Methylobacter marinus A45(T). The strain UCM B-3159 has lower coefficients of similarity (97.4-96.4%) for other species of that genus. These strains are similar as to their phenotypical properties and form one branch on the dendrogram which demonstrates species relations of Methylococcaceae family, that permitted reclassifying M. ucrainicus as M. marinus. Phylogenetic analysis has confirmed the belonging of strains UCM B-3002 and UCM B-3494 to Methylococcus capsulatus species. Those strains were earlier related to this species on the basis of phenotype features.

High extracellular concentration of K+ stimulated methane oxygenation with Methylomonas rubra 15 [Russian character: see text], Methylococcus thermophilus 111 [Russian character: see text] and Methylococcus capsulatus 494 at neutral value of pH. That was determined by K+ arrival to the cells at neutral medium pH that resulted in the increase of pH difference between the exterior and interior sides of the membrane (ApH) and, respectively, in the increase of the methane oxygenation rate. Thus, methane monooxygenation depends on the availability of ion gradients on a membrane. Ionophores valinomycin and monensin inhibited methane oxygenation by the cells of Methylomonas rubra 15 [Russian character: see text] that evidenced for the methane oxygenation dependence on the protone-motive force which could be formed as the result both of protons displacement with oxygenation of methane monooxygenation products and of the gradient of potassium and sodium ions. Protonophore FCCP suppressed completely methane oxygenation in Methylococcus capsulatus 494 and M. thermophilus 111 [Russian character: see text] at neutral pH, and took no effect at the alkaline values of pH. This suggests that FCCP dissipates the proton-motive force and does not inhibit methane monooxygenase activity. The results obtained indicate that the process of methane oxygenation should be combined with energy generation in a form of the transmembrane electric charge (delta psi) and proton gradient (deltapH).

Strain Methylomonas rubra 15sh(T), deposited in several collections of microorganisms (NCIMB 11913(T) = UCM B-3075(T) = ACM 3303(T)), is the subject of numerous studies. However, the name of this strain is not valid, primarily due to the phenotypic similarity of the species M. rubra to the species M. methanica. The results of the present study and data available in the literature indicate that M. rubra deserves the status of a separate species. Strains of M. rubra differ from strains of M. methanica in a number of properties, such as the ability to reduce nitrates to nitrites, the structure of intracytoplasmic membranes, and the presence of a new coenzyme Q. The distinctions between the species M. rubra and M. methanica were confirmed by comparison of electrophoretic patterns of their cellular proteins, by results of DNA-DNA hybridization, and by the data from 16S rRNA gene sequencing (the level of phylogenetic homology between these two species was below 95%). Phylogenetic and phenotypic analyses showed that strains of M. rubra cannot be assigned to any species of the genus Methylomonas. Results of polyphasic analysis suggest an independent taxonomic status of strain Methylomonas rubra 15sh(T). This paper contains description of Methylomonas rubra sp. nov. with the type strain 15sh(T) = NCIMB 11913T = UCM B-3075(T) = ACM 3303(T). The nucleotide sequence of the 16S rRNA gene of strain 15sh(T) has been deposited with the GenBank database under the accession number AY995198.

The authors have performed sequence-analysis of 16S rRNA genes of thermophylic methane-oxidizing bacteria UCM B-3026, UCM B-3032, UCM B-3109, UCM B-3014 which were isolated from sludge pond of different regions in Ukraine and deposited at Ukrainian Collection of Microorganisms (UCM) as Methylococcus thermophilus and "M. gracilis". A comparative analysis of 16S rRNA gene sequences of the studied bacteria with those sequences of various strains of bacteria in the GenBank databases has shown that the level of similarity of the strains UCM B-3026, UCM B-3032, UCM B-3109 with Methylocaldum szegediense was 98.0-98.7%, strain UCM B-3014 with Methylocaldum gracile--99.1%, that allows to relate them to these species. As to other species of the genus Methylocaldum, these strains had a lower level of similarity (94.8-97.2 %) and with Methylococcus thermophilus ACM 3585T (= IMV-B-3037T = UCM B-3037T)--less than 90%. Thus, the strains UCM B-3026, UCM B-3032, UCM-3109 were reclassified as Methylocaldum szegediense, strain UCM B-3014--as Methylocaldum gracile. When constructing phylogenetic tree based on the comparison of 16S rRNA genes with the use of various algorithms realized in the packages of programs Tree View (version 1.5.2) and ClastalX (version 1.81) certain clusters have formed genera Methylocaldum, Methylococcus and Methylomonas. Genera Methylobacter and Methylomicrobium have formed three clusters, one of the clusters contained two species of Methylobacter and two species of Methylomicrobium. Apparently, the taxonomy of genera Methylobacter and Methylomicrobium is to be specified.

Species status of the already described methylotrophic bacteria has been specified, and new isolates have been identified. The bacteria under study are classified as those from Methylobacterium genus on the basis of a set of diagnostic characteristics (they are capable to assimilate, besides methanol, other organic substances; to realize serine cycle of one-carbon compounds assimilation, to form rast-coloured colonies; they can form rosy-coloured colonies). As a result of the study of phenotypical characteristics in 14 strains of Methylobacterium and sequence-analysis of the gene 16S pRNA two strains: T-2 (=UKM B-3357) and strain ch-8 (=UKM B-3352) are identified as M. mesophilicum, strain A-5 (=UKM B-3381)--as M. extorquens; several strains were reclassified. The strain 9-17 (=UKM B-3339) is related to the species M. zatmanii (described before as M. organophilum), strain 13-17 (=UKM B-3342)--to the species M. fujisawaense (formerly--M. organophilum), K-2 (=UKM B-3351)--to the species M. fujisawaense (formerly--M. extorquens). Phenotypical characteristics differentiating the studied species of Methylobacterium are suggested. Identification of the strains of Methylobacterium genus based on sequence analysis of genes 16S pRNA is in agreement with the results obtained when studying phenotypical properties.

Psychrotolerant bacteria which use obligately methane were found in the moss samples and in soil-vegetation samples in the island part of the Antarctica during the VII expedition (2003) at the station "Akademik Vernadsky". The number of methane-oxidizing bacteria in the samples from the Antarctica (101- 10(3)/g of the sample) was lower than in the samples from the regions with moderate climate (10(2)- 106/g of the sample). Psychrotolerant strains of Methylobacteriium genus which use facultatively methanol were found in the bottom sediments of the fresh-water and Krasnoye lakes, as well as in the soil-plant samples. The psychrophilic strain which is probably a new species of the genus Methylobacterium has been isolated from one soil-plant sample from the Antarctica at 10 degrees C. It is established that most collection mesophilic strains of Methylobacterium, which have been isolated from the soil and plant phyllosphere in Ukraine, also could grow at 10 degrees C.

It has been shown that after DNA-injuring factors (UV irradiation or drying) action on soil one could observe the decrease of the total quantity of bacteria and the number of species, i.e., the decrease of microbe diversity. At the same time not numerous species were found in soils after their action. Thus the drying or UV-irradiation makes it possible to estimate more completely the microbe diversity in soils as well as to find resistant bacteria. It has been established that the strain Methylobacterium extorquens, M. mesophilicum, Bacillus subtilis, B. cereus, which were isolated after UV irradiation or drying of oil samples, were characterized by high resistance to gamma-irradiation (LD99.99--5-10 kGr). Bacteria (representatives of Pseudomonas genus) sensitive to drying or UV-irradiation were also sensitive to ionizing radiation (LD99.99--0.09 kGr). Nocardieforms and representatives of Myxococcus occupied intermediate position between representatives of genera Methylobacterium and Pseudomonas as to resistance to the above-mentioned stress agents.

The drying of soil samples reduced the abundance (especially of predominant species) and the diversity of bacteria isolated from these samples, making easier the isolation of rare bacterial species. Some bacterial species that were minor before soil drying became dominant in dried soil samples. In general, soil drying allowed the diversity of soil bacteria to be determined more adequately. The bacteria that were isolated from dried soil samples turned out to be resistant to gamma radiation (with LD90 = 2.8-4.6 kGy) and desiccation. It is concluded that soil drying may serve as a model for the action of stress factors on natural bacterial populations. The hypothesis that periodic desiccation was the primary cause of formation of bacterial radioresistance in nature is discussed.

Historical aspects of development of phylogenetic bacteria taxonomy and essence of species in systematics of bacteria are considered. Comparative analysis of phenotypic and phylogenic classification of bacteria is conducted. Basic results of 16S rRNA gene sequence for bacteria are adduced. Comparative estimation of molecular biological methods in microbiologic researches and also estimation of potentialities and shortcomings of 16S rRNA gene sequence-analysis in systematics of bacteria are conducted.

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.

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.

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.

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.

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.

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.

The diversity of aerobic chemoorganotrophic (capable of growing on nutrient agar) bacteria in radioactive soil (0.3-17.0 microCi/kg soil) sampled in the 10-km zone around the Chernobyl Nuclear Power Plant (CNPP) was found to be lower than that observed in control, uncontaminated soil with a radioactivity of 0.002-0.006 microCi/kg soil. All the radioactive soil samples contained the bacteria Bacillus cereus and Methylobacterium extorquens or M. mesophillicum, which exhibited a high tolerance to 0.3-1.0 M hydrogen peroxide, whose action can to a certain extent simulate the effect of ionizing radiation. Some of the contaminated soil samples contained other species of chemoorganotrophic bacteria with a low tolerance to H2O2. The survival of bacteria in the Chernobyl accident zone is probably due to the functioning of mechanisms efficiently neutralizing peroxide compounds and repairing radiation-damaged DNA. The population of cellulolytic, nitrifying, and sulfate-reducing bacteria in contaminated soil was found to be 1-2 orders of magnitude less than in control soil, indicating the unfavorable effect of anthropogenic radiation on the abundance and diversity of soil bacteria.