Yu. A. Nikolaev

Winogradsky Institute Of Microbiology, Moskva, Moscow, Russia

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Publications (40)29.33 Total impact

  • Yu. A. Nikolaev
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    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.
    Microbiology 04/2012; 69(3):291-295. · 0.71 Impact Factor
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    Yu. A. Nikolaev, J. I. Prosser
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    ABSTRACT: Two factors affecting the adhesionof Pseudomonas fluorescens to glass surfaces were revealed in the culture liquid (CL) of this bacterium. One of these factors, adhesin, which is responsible for cell adhesion, was found to be a protein substance located both at the cell surface and in the CL. Bacterial cells grown in rich LB medium were less adhesive than cells grown in minimal M9 medium. The adhesive capacity of cells was independent of the growth phase. The other factor, antiadhesin (AA), which reduces cell adhesion, was found only in the CL. AA concentration in the CL increased with the culture age.
    Microbiology 04/2012; 69(2):186-190. · 0.71 Impact Factor
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    Yu. A. Nikolaev, P. A. Fomin
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    ABSTRACT: The hypothesis of the Tunguska event as an explosion of a toroidal cloud formed by a single ejection of methane into the atmosphere was developed, comprehensively analyzed, and confirmed. The explosion was initiated by a slow- and flat-moving small meteorite. The gas-hydrate nature of the methane ejection was established, and the area was determined from which the ejection occurred. The trajectories of the meteorite and its maximum and minimum dimensions were estimated. The most probable area of the meteorite fall was determined. A statistical analysis was performed of a model experiment on forest fall (explosion of a detonating cord in the form of a ring over a forest of wires). The fall of wires was shown to be not only similar in appearance but also statistically equivalent to the real pattern of tree fall. An explanation is given to the light, acoustic, and atmospheric effects (silver clouds, ozone layer, and magnetic storm) associated with the Tunguska event. The absence of a significant amount of meteoritic material in the epicenter is explained. Taken together, these results confirm the hypothesis under consideration, are consistent with available evidence and provide a physically correct explanation of all features of the Tunguska phenomenon. KeywordsTunguska explosion–Tunguska meteorite
    Combustion Explosion and Shock Waves 03/2011; 47(2):226-240. · 0.49 Impact Factor
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    ABSTRACT: Kinetic characteristics of model enzymes and physicochemical properties of globular proteins modified by chemical analogues of low-molecular-weight microbial autoregulators (alkylhydroxybenzenes, AHBs) have been studied. C7 and C12 AHB homologues were used, differing in the length of the alkyl radical and the capacity for weak physicochemical interactions. Both homologues affected the degree of protein swelling, viscosity, and the degree of hydrophobicity. The effects depended on the structure of AHBs, their concentration, and pH of the solution, which likely reflects changes in the charge of the protein globule and its solvate cover. Variations of hydrophobicity indices of AHB-modified enzymes (trypsin and lysozyme) were coupled to changes in the catalytic activity. The values of K M, measured for the enzymes within both AHB complexes, did not change, whereas V max increased (in the case of C7 complexes) or decreased (C12 complexes). Possible molecular mechanisms of changes in the physicochemical and catalytic parameters of enzymatically active proteins, induced by modification with structurally distinct AHBs, are described, with emphasis on targeted regulation of functional activity.
    Applied Biochemistry and Microbiology 03/2011; 44(2):143-150. · 0.66 Impact Factor
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    ABSTRACT: The growth characteristics of an algo-bacterial community (Chlamydomonas reinhardtii and bacterial satellites) were studied, as well as the mechanism and patterns of bacterial effect on algae. Four strains of predominant bacteria were isolated and partially characterized. They were assigned to the following taxa: Rhodococcus terrea, Micrococcus roseus, and Bacillus spp. A pure culture of the alga under study was obtained by plating serial dilutions on agarized media. Within the algo-bacterial association, the alga had a higher growth rate (0.76 day−1) and yield (60 μg chlorophyll/ml culture) than in pure cultures (0.4 day−1 and 10 μg chlorophyll/ml culture, respectively). The viability of the algal cells within the association was retained longer than in pure culture. Among the isolated bacterial satellites, strains B1 and Y1, assigned to the species Rhodococcus terrae, had the highest stimulatory effect on algal growth. The culture liquid of bacteria incubated under the conditions not permitting growth stimulated algal growth; the culture liquid of actively growing bacteria had an opposite effect. Key wordsalgo-bacterial community– Chlamydomonas reinhardtii –growth stimulation–mechanisms of interaction
    Microbiology 02/2011; 77(1):78-83. · 0.71 Impact Factor
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    ABSTRACT: The influence of three chemical chaperones: glycerol, 4-hexylresorcinol, and 5-methylresorcinol on the structure, equilibrium fluctuations, and functional activity of the hydrophilic enzyme lysozyme and the transmembrane reaction center (RC) protein from Rb. sphaeroides in a broad range of concentrations has been studied. The chosen chemical chaperones differ strongly in their structure and action on hydrophilic and membrane proteins. The influence of the chemical chaperones (except methylresorcinol) on the structure, dynamics, and functional properties of lysozyme and RC protein are well described in the framework of extended models of preferential hydration and preferential interaction of protein with a chemical chaperone. A molecule of hexylresorcinol consists of a hydrophobic (alkyl radical) and a hydrophilic (aromatic core) moieties; this provides for additional regulation of the functional activity of lysozyme and RC by hexylresorcinol. The influence of methylresorcinol on proteins differs from that of glycerol and hexylresorcinol. Methylresorcinol interacts with the surface of lysozyme directly, not via water hydrogen bonds. This leads to a decrease in the denaturation temperature and an increase in the amplitude of equilibrium fluctuations, allowing it to be a powerful activator. Methylresorcinol interacts with the membrane RC protein only by the condensation of hydration water, which is negligible in this case. Therefore, methylresorcinol does not affect the functional properties of the RC protein. It is concluded that different chaperones at the same concentration as well as one and the same chaperone at different concentrations produce protein 3D structures differing in dynamic and functional characteristics. Keywordslysozyme–reaction center protein– Rhodobacter sphaeroides –chemical chaperone
    Biophysics 02/2011; 56(1):8-23.
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    Pavel Fomin, Yu.A. Nikolaev
    Физика горения и взрыва. 01/2011; 47(2):112-127.
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    ABSTRACT: The adaptogenic effect of the chemical analogues of alkylhydroxybenzenes (AHBs), bacterial extracellular autoregulators (the individual compound C7-AHB and its technical preparation Sidovit), was demonstrated for two pseudomonad species, Pseudomonas aeruginosa and P. fluorescens. The protective effect of AHBs resulted in increased growth rate and biomass accumulation in bacteria grown under suboptimal conditions within the species tolerance range. The adaptogenic effect of AHBs (10–50 μmg/l) was more pronounced under more unfavorable growth conditions. In the case of P. fluorescens, the individual compound C7-AHB increased the biomass yield by 30% under alkaline conditions (pH 9.5), when the growth rate decreased by 80–90% compared to the optimum (pH 5.5–7.5). The Sidovit preparation, containing a mixture of natural AHBs with C7-AHB as the main component, increased the growth rate of P. aeruginosa by 40–60% at nonoptimal temperatures (45 and 10°C) or under enhanced salinity (1% NaCl). The action of AHBs as regulators of the rpoS and SOS response stress regulons was demonstrated to be among the mechanisms of their adaptogenic effect, as was demonstrated with the relevant reporter genes in the model strains E. coli C600 thi, thr, leuΔ(pro-lac) with the osmE-lacZ and umuD-lacZ hybrid operons, respectively. AHBs are technologically and economically acceptable as adaptogenic supplements for bacterial preparations used in soil bioremediation and oil spillage removal under conditions unfavorable for microbial growth, including increased salinity, extreme pH, and fluctuating sub- or supraoptimal temperatures. Keywordsbacteria-stress-adaptation-alkylhydroxybenzenes-protectors-efficiency of bacterial preparations-soil bioremediation
    Microbiology 12/2010; 79(6):747-752. · 0.71 Impact Factor
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    ABSTRACT: Overdriven detonation waves allow one to produce coatings of high-melting powder materials and improve the quality of coatings sprayed from lower-melting-point materials. The kinetic and thermal energies of detonation products behind the front of overdriven detonation waves are much higher than those behind the front of self-sustained Chapman-Jouguet detonation waves traditionally used in spray processes. This paves the way toward the design of small-size spraying guns including those for applying coatings on the inner surfaces of parts.
    Combustion Explosion and Shock Waves 05/2010; 46(3):352-359. · 0.49 Impact Factor
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    ABSTRACT: The connection between the efficiency of phenolic lipids and their hydrophobic property (solubility) and hydrophobic property of microorganisms’ cell structure is shown. The mixture of amphiphilic di(oxiphenil)-phenil-methanes, which act bacteriostatically under 15 mg/l, possesses maximal efficiency against Staphylococcus aureus. Against Mycobacterium smegmatis with hydrophobic cell wall, hydrophobic 2,4-dialkylocibenzol 70 mg/l was the most effective. Hexylresorcin (HR) stops the development of gram-positive bacteria in concentrations 20–50 mg/l, that of gram-negative bacteria in concentration 65 mg/l, that of M. smegmatis at 70 mg/l, and that of yeast and fungi at 300 mg/l. HR prevails bacteria spores germination in the concentration 25–100 mg/l. The dependence of antibacterial action of isomers and homologues of alkylresorcins on their structure-number, position, and length of alkyl substituents-is studied.
    Applied Biochemistry and Microbiology 03/2010; 46(2):159-165. · 0.66 Impact Factor
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    ABSTRACT: Alkylhydroxybenzenes (AHB) were found to control the activation of protective functions of microorganisms by inducing stress gene expression and increasing the frequency of the intrapopulation phase transitions which are responsible for the phenotypic variability of bacteria. We established the dependence of the regulatory effects of AHB on their structure (alkyl radical length) and concentration. A reversion assay using the tryptophan auxotrophic strain Bacillus subtilis trpA5 B 1733 indicated a relationship between the reversion frequency that was 40–120 times higher than the background value and phase transition’s intensity (with R → S transition rates up to 87% in contrast to 2% in the control experiment) induced by specific doses (5–100 mg/ml) of long-chain AHB such as C12-AHB acting for a short time (1 h) on vegetative (dividing or stationary-phase) B. subtilis cells. Using four test strains constructed from Escherichia coli C600 thi, thr, leuΔ(pro-lac) with transcriptional or translational vectors containing the hybrid umuD-lacZ or osmE-lacZ operons, we demonstrated that AHB perform the regulatory functions involved in controlling the SOS response gene expression and the general rpoS -dependent stationary-phase regulon, respectively. The dose-dependent effect of long-chain AHB (within the 50–100 µg/ml range) resulting in a two- to threefold increase in the stress gene expression, similar to the effect of natural stress factors such as UV irradiation and starvation, provides evidence that AHB function as alarmones (danger signals). From the fact that the osm E gene is upregulated by 35–70 µg/ml C12-AHB (its regulation level is increased up to twofold), it follows that C12-AHB controls rpoS-dependent regulation and the transition to the stationary phase. The effect of the short-chain homologue C7-AHB substantially differs from that of C12-AHB. C7-AHB in concentrations of 10–100µg/ml causes a significant decrease in osmE and umuD expression. A 30-min preincubation of cells with 10–100µg/ml C7-AHB protected them from UV irradiation, as was observed as a 3.6-fold decrease in umuD expression. Comparative analysis of the marker gene’s expression values in the strains with the transcriptional and translational vectors demonstrates that AHB nonspecifically activate stress regulons at the transcription level.
    Microbiology 12/2009; 78(6):678-688. · 0.71 Impact Factor
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    ABSTRACT: Experiments and simulations to achieve high values of plasma parameters at the Globus-M spherical tokamak (ST) at moderate absolute auxiliary heating power (up to 0.8 MW) and high specific heating power (up to 2–3 MW m−3) are described. Important distinguishing features are the low edge safety factor range, which is unusual for STs, 2.7 < q < 5 and small plasma–outer wall space (3–5 cm). High ion heating efficiency with neutral beam injection (NBI) was demonstrated. Results of numerical simulation of fast ion trajectories are described and fast ion generation during the NBI and ion cyclotron resonance heating is discussed. Investigations on their confinement and slowing down are also presented. Reasons for achievement of high IC heating efficiency are outlined. Reliable H-mode regime achievement is described. Transport ASTRA modelling demonstrated that during NB heated H-mode ion heat diffusivity remains neoclassical and the particle diffusion coefficient inside transport barrier decreases significantly. Analysis was performed of divertor tile and special probe surfaces after irradiation by plasma during a large number of shots (3000–10 000 shots). Mixed layer composition is measured and deuterium retention in different tokamak first wall areas is estimated. Plasma jet injection experiments with upgraded plasma jet are described. Jet penetration to the plasma centre with immediate increase of density and temperature drop is proved and analogy with pellet injection is outlined.
    Nuclear Fusion 09/2009; 49(10):104021. · 3.24 Impact Factor
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    ABSTRACT: The composition, morphology and structure of the mixed layers deposited onto the surface (deposits) after a preliminary carboboronization procedure (B/C : H layers deposition) and subsequent plasma–wall interaction in the different areas of the Globus-M spherical tokamak have been analysed. Globus-M is almost completely covered by recrystallized graphite protection tiles (currently about 90% of its inner vessel area facing to plasma). The deposit properties were examined by different diagnostic techniques (electron probe microanalysis, scanning electron microscope, x-ray diffraction, nuclear resonance reactions, thermal desorption spectroscopy, infrared Raman scattering and secondary ion mass spectroscopy) after sample exposure to plasma during 3000–10000 tokamak pulses. It was found that deposits existed even in high flux regions (separatrix strike points). The initial composition of the protective layers formed during boronization is dramatically modified during long-term plasma–wall interaction and resulted in significant intermixing of its components with materials of the vessel interior. The properties of the layers deposited onto the surfaces intensively interacting with plasma, as well as the composition of the layers deposited in the 'shadowed' zones are discussed. Deuterium retention in Globus-M was estimated relying upon the data on deuterium concentrations in the deposits that were measured by different methods. It is revealed that deuterium was absorbed only in the deposits and its concentration vanished in the bulk of the tiles. Conditions of deuterium desorption are analysed and the merits of recrystallized graphite are discussed.
    Nuclear Fusion 09/2009; 49(9):095022. · 3.24 Impact Factor
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    ABSTRACT: In our study, we investigated the capacity of alkylhydroxybenzenes (AHB), which are microbial anabiosis autoinducers, for alteration of the enzymatic activity of the hen egg-white lysozyme, as well as the efficiency of hydrolysis of specific (peptidoglycan) and nonspecific (chitin) substrates catalyzed by lysozyme. AHB homologues (C7-AHB and C12-AHB), which differ in their hydrophobicity and effects in their interaction with lysozyme, were used as modifying agents. C7-AHB stimulated enzymatic activity within the whole range of concentrations used (10−7−10−3 M). More hydrophobic C12-AHB exhibited this ability only at low concentrations and inhibited fermentative activity at high concentrations, acting as a mixed-type inhibitor. Both AHB homologues caused changes in the hydrophobicity of lysozyme molecules. An increase in the affinity level between the C7-AHB-modified enzyme and the nonspecific substrate (colloidal chitin or cell wall polymers of Saccharomyces sp.) was observed, which manifested itself in the enhancement of the hydrolysis rate by 200–500% (as compared to the native enzyme). A significant effect on the efficiency of the lysozyme-catalyzed modifications of the substrate (peptidoglycan, colloidal chitin) structure as a result of its complexation with AHB was demonstrated. A stabilizing effect of C7-AHB and C12-AHB was revealed, which ensured a high level of activity of the AHB-modified enzyme (as compared to the control) after heat treatment (functional stability), as well as at nonoptimal temperatures of catalysis (operational stability). The biological significance of lysozyme modification with AHB and the practical aspects of its application are discussed.
    Microbiology 04/2009; 78(2):144-153. · 0.71 Impact Factor
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    ABSTRACT: The effect of hexylresorcinol (HR), a chemical analogue of microbial anabiosis autoinducers of the alkylhydroxybenzene (AHB) group, on the stability of biological membranes and monolamellar liposomes formed of egg phosphatidylcholine (ePC) was studied. According to spectrophotometry and electron microscopy studies of HR-loaded liposomes in the presence of a surfactant Tween 20, the critical ratio between HR and ePC for liposome preservation was found to be close to equimolar. The trends in HR influence on membrane structural organization and stability of liposomes were also confirmed in experiments on intact bacterial cells explaining non-species-specific effect of AHBs. The demonstrated high efficiency of AHB biocides may be used in material and equipment protection against biocorrosion.
    Applied Biochemistry and Microbiology 02/2009; 45(2):162-168. · 0.66 Impact Factor
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    ABSTRACT: The effect of alkylhydroxybenzenes (AHBs) belonging to the class of alkylresorcinols differing in the degree of hydrophobicity—C7-AHB and more hydrophobic C12-AHB—on the resistance of Saccharomyces cerevisiae cells to heat shock and oxidative stress of lethal intensity was studied. Depending on structure and concentration, AHB added 2 h before exposure to stress had either an antistress or stress-potentiating effect on yeast cells in the mid-logarithmic growth phase. C7-AHB at concentrations 0.25–0.5 g/l caused a two-to fivefold increase in the resistance of yeast cells to hydrogen peroxide (30–150 mM), whereas C12-AHB reduced it at all concentrations. C7-AHB and C12-AHB had a similar effect on yeast subjected to heat shock (45°C, 30 min). It was found that the degree of the protective effect of C7-AHB and potentiating effect of C12-AHB depended on the nature of the stressor, being more pronounced in heat shock. The environmental significance of the antistress and stress-potentiating effects of microbial AHBs is discussed.
    Applied Biochemistry and Microbiology 08/2008; 44(5):518-522. · 0.66 Impact Factor
  • T. P. Gavrilenko, Yu. A. Nikolaev
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    ABSTRACT: A model of processes in the barrel of a detonation facility for application of powder coatings, which takes into account the variable composition of the working gases in the barrel, is presented. It is demonstrated that varying the volume of the gas mixer is an effective tool for stabilizing particle parameters and coating properties if powders with wide fractions are used. The code proposed is a convenient instrument for predicting coating properties.
    Combustion Explosion and Shock Waves 11/2007; 43(6):724-731. · 0.49 Impact Factor
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    ABSTRACT: The changes in the state of Bacillus subtilis spores that occur during germination were analyzed using dynamic phase microscopy (DPM). DPM is based on monitoring and analyzing the interference image of a specimen in a coherent laser beam. The optical path difference (the phase thickness of the specimen, PT) depends on the geometrical height of the specimen and its refractive index. We demonstrated that the maximum PT value is a convenient criterion of the physiological state of the organism involved: PT is ≥ 80 nm, ∼40–50 nm, and ≤ 20 in dormant, developing (initiated), and heat-killed spores, respectively. We established that (i) heating a spore suspension to 40°C results in a reversible twofold decrease (from 80 to 40 nm) in their PT under conditions that do not promote the development of the bacteria; this decrease is irreversible under growth-promoting conditions; (ii) the PT values of germinating spores oscillate with a considerable fluctuation amplitude (up to 7 nm), in contrast to the limited fluctuation amplitude (within 1 nm) in dormant spores; (iii) activated spores were heterogenous with respect to the PT pattern: a majority of the spores exhibited a usual spatial profile (with a maximum thickness in the center), whereas a minor fraction of them were characterized by an erythrocyte-like profile with a concave center; this implies that the central zone of the spore was more rapidly hydrated (with a decrease in refractive index) than the peripheral zone.
    Microbiology 04/2007; 76(2):164-171. · 0.71 Impact Factor
  • T. P. Gavrilenko, Yu. A. Nikolaev
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    ABSTRACT: The maximum possible values of adhesion and cohesion are calculated for a number of powder materials, substrate materials, sizes of installation barrels, and compositions of explosive gas mixtures. These data give a clear idea about the areas of applicability of gaseous detonation spraying.
    Combustion Explosion and Shock Waves 09/2006; 42(5):594-597. · 0.49 Impact Factor
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    ABSTRACT: Examples are considered of the involvement of low-molecular-weight autoregulators in the development of resistance of proliferating microbial cultures to unfavorable environmental impacts of various intensity, including impacts programmed to occur in the developmental cycle (“new medium stress,” starvation stress) and nonprogrammed impacts. It was shown that extracellular adaptation factors control the reversible adhesion of cells in submerged cultures and the processes of cell reactivation in the poststress period and are involved in the stabilization of cellular biopolymers (proteins and DNA) and subcellular structures (membranes); the adaptogens of the phenolic type also act as efficient scavengers of reactive oxygen species. The protective effect of the adaptogenic autoregulators is manifested in the increase of resistance of microbial cells to stressors of various nature and in the preservation of the cell proliferative ability.
    Microbiology 07/2006; 75(4):420-426. · 0.71 Impact Factor

Publication Stats

149 Citations
29.33 Total Impact Points

Institutions

  • 2004–2011
    • Winogradsky Institute Of Microbiology
      Moskva, Moscow, Russia
    • A. N. Frumkin Institute of Physical Chemistry and Electrochemistry
      Moskva, Moscow, Russia
  • 1997–2011
    • Russian Academy of Sciences
      • • Ioffe Physical-Technical Institute
      • • Institute of Microbiology
      Moskva, Moscow, Russia
  • 2009
    • Ioffe Physical Technical Institute
      Sankt-Peterburg, St.-Petersburg, Russia
  • 2002
    • Yaroslavl State University
      Jaroslawl, Jaroslavl, Russia