[Show abstract][Hide abstract] ABSTRACT: Effect of sublethal doses of physical and chemical stressors (heat shock for 2 h at 45°C and addition of C12-alkylhydroxybenzene, a microbial alarmone) on development of resistance to the subsequent lethal antibiotic attack and the role of the time interval between these treatments were studied on a submerged batch culture of Escherichia coli K12. The interval sufficient for the development of stress response provides for development of temporary adaptive resistance to the antibiotic attack, resulting in increased number of surviving persister cells. The interval below the time required for the stress response potentiates cell death and results in a decreased number of persisters. Heterogeneity of the fractions (10–4 to 10–2% of the initial CFU number) surviving lethal doses of an antibiotic (ampicillin or ciprofloxacin) was found. Apart from a low number of antibiotic-resistant cells (up to 0.005% of surviving cells), the fractions contained antibiotic-tolerant forms, such as temporarily resistant metabolically adapted cells, long-term surviving persisters, and the cells of slowly growing SCV variants with small colonies (d ≤ 1 mm). Persisters are hypothesized to act as precursors for cystlike dormant cells (CLC), in which the cell differentiation stage is completed and the processes of cell ametabolism (transition to the anabiotic state) are still incomplete.
[Show abstract][Hide abstract] ABSTRACT: Efficiency of MALDI mass spectrometry for differentiation between phenotypic phase variants (in colony morphology and virulence/avirulence) was investigated for saprotrophic and opportunistically pathogenic bacteria of five genera (Acinetobacter, Arthrobacter, Rhodococcus, Corynebacterium, and Escherichia). Analysis of MALDI spectra (on the SA and HCCA matrices) included (1) determination of similarity of the protein spectra as a percentage of the common protein peaks to the total amount of proteins, which reflects the phylogenetic relationships of the objects and has been recommended for identification of closely related species; (2) comparison of intensities of the common peaks; and (3) the presence of specific peaks as determinative characteristics of the variants. Under the standard analytical conditions, the similarity between the MALDI profiles was shown to increase in the row: genus-species-strain-variant. Assessment of intensities of the common peaks was most applicable for differentiation between phase variants, especially in the case of high similarity of their profiles. Phase variants (A. oxydans strain K14) with similar colony morphotypes (S, R, M, and Sm) grown on different media (LB agar, TSA, and TGYg) exhibited differences in their protein profiles reflecting the differences in their physiological characteristics. This finding is in agreement with our previous results on screening of the R. opacus with similar colony morphology and different substrate specificity in decomposition of chlorinated phenols. Analysis of MALDI spectra is probably the only efficient method for detection of such variants.
[Show abstract][Hide abstract] ABSTRACT: A new species of bacteria oxidizing ammonium with nitrite under anoxic conditions was isolated from the activated sludge of a semiindustrial bioreactor treating digested sludge of the Kuryanovo wastewater treatment plant (Moscow, Russia). Physiological, morphological, and molecular genetic characterization of the isolate was carried out. The cells were ovoid (~0.5 × 0.8 μm), with the intracellular membrane structures characteristic of anammox bacteria (anammoxosome and paryphoplasm); unlike other anammox bacteria, it possessed extensive intracellular membrane structures located in layers parallel to the cytoplasmic membrane, but never close to the anammoxosome. The cells formed aggregates 5–28 μm in diameter and readily attached to solid surfaces. The cells were morphologically labile, easily plasmolyzed, and lost their content. Doubling time was 28 days, μmax = 0.025 day–1; optimal temperature and pH for growth were 20–45°C and 8.0, respectively. Phylogenetic analysis of the 16S rRNA gene sequences suggested its classification as a new species of the candidate genus Jettenia (order Planctomycetales). The name Candidatus “Jettenia moscovienalis” sp. nov. was proposed for the new bacterium.
[Show abstract][Hide abstract] ABSTRACT: The paper presents results of study of anoxic ammonia oxidation at low temperature conducted at JSC Mosvodokanal, Moscow, Russia. The study was carried out in two reactors, 5 l each, operated at the temperature of 5–10 °С. Both reactors were inoculated with the soil, collected from waste water sludge landfill, that presumably, contained low-temperature adapted nitrifying bacteria. Reactor No. 1 contained nitrifying bacteria only. Reactor No. 2 was further inoculated by anammox bacteria. Filtrate from digested sludge belt thickeners was added into the reactors to achieve a final N-NH4 concentration of 70–95 mg/l. The reactors were operated as sequencing batch reactors. After 90 days of incubation maximal nitrification rate in reactor No. 1 was 1.4 mg N-NH4/g VSS*h, and in reactor No. 2–1.0 mg N-NH4/g VSS*h. Estimated doubling time of nitrifying bacteria was 45 days. Total mineral nitrogen removal in the 1st reactor was 20% (via process of heterotrophic denitrification), and in the 2nd – 60% (via both the processes of heterotrophic and autotrophic nitrate reduction). Through the process of autotrophic denitrification (anammox), two times as much nitrogen was removed, compared to the heterotrophic denitrification process. Anammox process rate was 0.4 mg N-NH4/g VSS*h.
Water Practice & Technology 03/2015; 10(1):172. DOI:10.2166/wpt.2015.019
[Show abstract][Hide abstract] ABSTRACT: Low content of ammonia in the treated water is one of the most important indicators of the efficiency of biological wastewater treatment. Oxidation of ammonium to nitrate (nitrification) is carried out by nitrifying bacteria, which have low growth rates and are very sensible to certain unfavorable technological factors, such as low oxygen concentration and toxicants). To stabilize the number of nitrifying bacteria, increasing their activity in bioreactors with activated sludge and, therefore, to achieve stable and efficient removal of nitrogen compounds, various techniques are used, one of which is bioaugmentation technology. Bioaugmentation implies addition of the necessary microorganisms or creation of the conditions favoring their development in order to increase the specific activity of biological systems, such as activated sludge. In the Engineering and Technological Centre of JSC ‘Mosvodokanal’ for the first time in world practice, we studied the efficiency of nitrification in a plant operating under the scheme of the University of Cape Town process, in combination with an additional bioaugmentation reactor. Activated sludge in the reactor was enriched with nitrifying bacteria. At higher ammonium loads, which were modeled by adding the liquid phase of digested sludge, the main line did not remove ammonium to the maximum permissible concentration for fishery water bodies. The use of a bioaugmentation reactor resulted in ammonium concentration decrease from 40-50 to 0.4 mg N-NH4/l. This approach increased the stability of the activated sludge nitrifying bacteria to toxicants (thiourea).
Water Practice & Technology 12/2014; 9(4):551. DOI:10.2166/wpt.2014.061
[Show abstract][Hide abstract] ABSTRACT: The contribution of the major technologically important microbial groups (ammonium- and nitrite-oxidizing, phosphate-accumulating, foam-inducing, and anammox bacteria, as well as planctomycetes and methanogenic archaea) was characterized for the aeration tanks of the Moscow wastewater treatment facilities. FISH investigation revealed that aerobic sludge were eubacterial communities; the metabolically active archaea contributed insignificantly. Stage II nitrifying microorganisms and planctomycetes were significant constituents of the bacterial component of activated sludges, with Nitrobacter spp. being the dominant nitrifiers. No metabolically active anammox bacteria were revealed in the sludge from aeration tanks. The sludge from the aeration tanks using different wastewater treatment technologies were found to have differing characteristics. Abundance of the nitrifying and phosphate-accumulating bacteria in the sludge generally correlated with microbial activity in microcosms and with efficiency of nitrogen and phosphorus removal from wastewater. The highest microbial numbers and activity were found in the sludge of the tanks operating according to the technologies developed in the universities of Hannover and Cape Town. The activated sludge from the Novokur’yanovo facilities, where abundant growth of filamentous bacteria resulted in foam formation, exhibited the lowest activity. The group of foaming bacteria included Gordonia spp. and Acinetobacter spp utilizing petroleum and motor oils, Sphaerotilus spp. utilizing unsaturated fatty acids, and Candidatus ‘Microthrix parvicella’. Thus, the data on abundance and composition of metabolically active microorganisms obtained by FISH may be used for the technological control of wastewater treatment.
[Show abstract][Hide abstract] ABSTRACT: The work deals with more efficient procedures for the isolation and cultivation of "nonculturable" microorganisms (NM) from environmental sources. The techniques for NM cultivation in situ and under laboratory conditions are discussed. A new approach is considered, viz., cultivation under cyclically varying conditions with the cycle duration comparable to the duration of the cell cycle. Cyclic cultivation implies sequential changes of several cultivation phases with different growth conditions. An established sequence of growth phases provides for the competitiveness of the target microorganisms and for accumulation of their biomass. Cultivation of phosphate-accumulating bacteria, nonculturable microorganisms which have not been previously isolated in pure culture, in an SBR reactor is discussed as an example of cyclic cultures.
[Show abstract][Hide abstract] ABSTRACT: Effect of the antibiotics kanamycin and ampicillin on the growth and phase variation of the populations of four strains of lactic acid bacteria (Lactobacillus sp. M76AT, L. casei MB, Enterococcus faecium M, and E. faecium M3185) was studied. The presence of antibiotics in the medium resulted in a dose-dependent decrease in viable cell numbers and in partial or complete substitution of the dominant S variant with the minor Sm and Sb variants. The variants differed in colony morphology, as well as in some physiological, biochemical, biotechnological, and probiotic characteristics. The Sm type variants of all strains exhibited the highest resistance to antibiotics. High production of exopolysaccharides was found in Sb variants of lactobacilli and in S variants of enterococci. The highest antibacterial activity was found in Sm variants of lactobacilli, especially in Lactobacillus sp. M76AT. The latter is biotechnologically the most promising strain, since all variants fermented milk yielding the products with uniformly pronounced functional and organoleptic properties. These patterns are of importance for the understanding of the mechanisms of antibiotic resistance and for selection of the variants with desired properties, as well as for quality control of the lactic acid bacteria starter cultures.
[Show abstract][Hide abstract] ABSTRACT: The annual dependences of the powers and energies generated by the unit area of a solar cell (SC) are calculated for a-Si:H-based SCs operating at latitudes of 45°N, 50°N, 55°N, and 60°N and in some geographical localities of Russia. Normalization of these dependences gives an idea about the corresponding annual dependences for SCs based on other semiconductors. Combined with the data on the average number of sunny days in a year (or the total duration of sunshine per year) for a specific region in Russia, this information makes it possible, in particular, to judge about the prospects for constructing solar power plants in these regions. As a result, the regions in Russia for which the excess over the average values of electrical energy generated by solar power plants may reach 24% are determined.
[Show abstract][Hide abstract] ABSTRACT: The time dependences of the key characteristic of a-Si:H solar cells over daylight hours are theoretically simulated. The model is used to calculate the time dependences for an arbitrary geographic latitude in the interval 30°–60° and arbitrary day of the year. The calculated results are illustrated for a geographic latitude of 45° and equinox. The relative variations in the characteristics of the a-Si:H solar cells are valid with a relatively high accuracy for the solar cells based on alternative semiconductors provided that their efficiency ranges form 7 to 20%.
[Show abstract][Hide abstract] ABSTRACT: A new genus and species of bacteria capable of ammonium oxidation under anaerobic conditions in the presence of nitrite is described. The enrichment culture was obtained from the Moscow River silt by sequential cultivation in reactors with selective conditions for anaerobic ammonium oxidation. Bacterial cells were coccoid, ∼0.4 × 0.7 μm, with the intracellular membrane structures typical of bacteria capable of anaerobic ammonium oxidation (anammoxosome and paryphoplasm). The cells formed aggregates 5–25 μm in diameter (10 μm on average). They were readily adhered to solid surfaces. The cells were morphologically labile: they easily lost their content and changed their morphology during fixation for electron microscopy. The organism was capable of ammonium oxidation with nitrite. The semisaturation constants Ks for nitrite and ammonium were 0.38 mg N-NO2/L and 0.41 mg N-NH4/L, respectively. The maximal nitrite concentrations for growth were 90 and 75 mg N-NO2/L for single and continuous application, respectively. The doubling time was 32 days, μmax = 0.022 day−1, the optimal temperature and pH were 20°C and 7.8–8.3, respectively. According to the results of 16S rRNA gene sequencing, the bacterium was assigned to a new genus and species within the phylum Planctomycetes. The proposed name for the new bacterium is Candidatus Anammoximicrobium moscowii gen. nov., sp. nov. (a microorganism carrying out anaerobic ammonium oxidation, isolated in the Moscow region).
[Show abstract][Hide abstract] ABSTRACT: The lipid composition of the microbial community inhabiting activated sludge in a pilot reactor for the anaerobic oxidation of ammonium (anammox) at the Kur’yanovo Treatment Plant (Moscow) has been studied. The fatty acid composition is mostly based on common fatty acids C14–C18 (95%) with both normal and isomeric structures. The biomass of activated sludge was found to contain lipids with the so-called ladderane substances (ladder alcohols and fatty acids) that are common for anammox bacteria: C20--lad-derane and C20--ladderane alcohols and C18- and C20--ladderane and C18- and C20--ladderane acids. In addition, the native extract contained both simple and compound ethers of the above-mentioned substances with residues of phosphocholine, phosphoethanolamine, and phosphoglycerine. The spectra of the electron impact and tandem mass spectrometry of certain substances have been obtained and published for the first time.
[Show abstract][Hide abstract] ABSTRACT: The distribution of material properties in a forged part used to make reference specimens was studied. The objective was to determine why the scatter of data was so large in tests of temperature reference specimens of VVER-1000 base metal on the metal of a sampling ring of a regular VVER-1000 casing. The tests were performed on Charpy and rupture samples, and the hardness was measured and the chemical composition studied. It is shown that the scatter is mainly due to the fact that the reference specimens of the VVER-1000 base metal were cut from the end of the forged part, where, characteristically, a property gradient exists along the vertical coordinate with the critical brittleness temperature decreasing significantly toward the top boundary of the forged part. The scatter of the initial critical brittleness temperature for the control and temperature groups was evaluated within the framework of a virtual experiment simulating a study of reference specimens with prescribed property variation.
Atomic Energy 04/2013; 113(6). DOI:10.1007/s10512-013-9656-4 · 0.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The paper presents an integrated agroecological assessment of sewage sludge produced by different processing technologies using the example of the South Butovo and Kuriyanov wastewater treatment plants in Moscow. The analysis indicates their conformity to standard requirements and the advantages of the novel sediment processing technology.
Moscow University Soil Science Bulletin 10/2012; 67(4). DOI:10.3103/S0147687412040047
[Show abstract][Hide abstract] ABSTRACT: The effect of returning solids to the digester, after one of three thickening processes, on volatile solids reduction (VSR) and gas production was investigated. Three different thickening methods were compared: centrifugation, flotation and gravitational sedimentation. The amount and activity of retained biomass in thickened recycled sludge affected the efficiency of digestion. Semi-continuous laboratory digesters were used to study the influence of thickening processes on thermophilic sludge digestion efficiency. Centrifugation was the most effective method used and caused an increase of VSR from 43% (control) up to 70% and gas generation from 0.40 to 0.44 L g(-1) VS. Flotation and gravitational sedimentation ways of thickening appeared to be less effective if compared with centrifugation. These methods increased VSR only by up to 65 and 51%, respectively and showed no significant increase of gas production. The dewatering capacity of digested sludge, as measured by its specific resistance to filtration, was essentially better for the sludge digested in the reactors with centrifugated and settled recycle. The VS concentration of recycle (g L(-1)), as reflecting the amount of retained biomass, appeared to be one of the most important factors influencing the efficiency of sludge digestion in the recycling technology.
[Show abstract][Hide abstract] ABSTRACT: The irradiation embrittlement and integrity of the VVER reactors has been an important issue in many EC supported TACIS and PHARE projects since 1990. In the EC annual programs two TACIS projects (TAREG 2.01/00 and 2.01/03) were launched on the issue in order to improve the neutron irradiation embrittlement databases, elaborate new trend curves for the embrittlement and to assess the integrity of the RPVs (Reactor Pressure Vessel) by analysing PTS transients (Pressurized Thermal Shock) for some selected Russian and Ukrainian VVER 1000 and 440/213 NPPs. In this paper the TAREG 2.01/00 project is briefly described with some details from the twin project 2.01/03, which served as a materials testing project, providing inputs for the 1st project. As a result of the project new trend curves for neutron irradiation embrittlement were elaborated, based on upgraded and more reliable surveillance results databases. The PTS study shows that the integrity of the selected VVER RPVs can be ensured to the end of RPV design life.
Progress in Nuclear Energy 07/2012; 58:52–57. DOI:10.1016/j.pnucene.2012.02.007 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The radiation embrittlement of reactor vessel materials is a complex process, which depends on the conditions of irradiation
and the microstructure and chemical composition of the steel. It is universally acknowledged that phosphorus, copper, and
nickel intensify the radiation embrittlement of vessel material the most. It is believed that Mn, N, C, Mo, Si, As, Sn, V,
and other elements also influence radiation embrittlement, but their effect has not been definitely established and is much
less than the effect of phosphorus, copper, and nickel. The presence of a synergetic interaction of elements in the irradiation
process and the complex interaction of metallurgical factors and the irradiation conditions make it difficult to determine
the degree to which impurities and alloying elements influence radiation embrittlement. The effect of the chemical composition
of steel, as one of the most important parameters determining the radiation service life of vessel material, on radiation
embrittlement is studied, 5 figures, 1 table, 20 references.
Atomic Energy 05/2012; 88(4):281-287. DOI:10.1007/BF02673611 · 0.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of distant interactions (LRI) and culture air on the adhesion ofPseudomonas fluorescens cells were studied. OneP. fluorescens culture was found to diminish the adhesion of cells of another, glassscreened,P. fluorescens culture by 30% (in the absence o air exchange between cultures). This effect was interpreted to be due to penetrating LRI.
Under the combined action ofLRI and culture air (the latter alone reduced cell adhesion by only several percent), the amount of unattached cells increased
2-to 30-fold (on the average, by a factor of nine). Such a great reduction of cell adhesion indicated the synergistic action
ofLRI and culture air.