Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Biochemistry and Microbiology (v.40, #3)
Stressors, Stress Reactions, and Survival of Bacteria: A Review by L. I. Vorob'eva (pp. 217-224).
Recent data on the molecular mechanisms of the stress responses of bacteria are reviewed, with emphasis on their reactions to a variety of stressors (heat, oxidation, cold, osmotic shock, etc.). The mechanisms underlying the phenomenon of sensoring are discussed. It is shown that cross-resistance to stressors and cell-to-cell communication, mediated by chemical metabolites, affect bacterial survival in food products. The stress-antagonizing activity of bacteria is discussed in relation to food product biotechnology.
Transformation of Phospholipids by Cabbage Phospholipase D in Mixed Micelles Containing 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate by V. M. Shnigir; M. A. Kisel' (pp. 225-230).
We compared the activities of cabbage phospholipase D during hydrolysis and transesterification of phosphatidylcholine in mixed micelles of surface-active compounds with various physicochemical properties. Mixed micelles of phospholipids and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (ratio, 1 : 2) were among the best substrates. Hydrolysis and transphosphatidylation were studied in micelles containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate. Mixed micelles of phosphatidylcholine and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate may serve as a new substrate for the measurement of phospholipase D activity and preparation of phospholipids using this enzyme.
Isolation and Partial Characterization of DNA Topoisomerase I from the Nucleoids of White Mustard Chloroplasts by G. G. Belkina; E. V. Pogul'skaya; N. P. Yurina (pp. 231-235).
DNA topoisomerase was isolated for the first time from nucleoids of white mustard (Sinapis alba L.) chloroplasts. The enzyme had a molecular weight of 70 kDa; was ATP-independent, required the presence of mono- (K+) and bivalent (Mg2+) cations, and was capable of relaxing both negatively and positively supercoiled DNA. These results suggest that the enzyme isolated belongs to the type IB DNA topoisomerases.
Conversion of L-Cystine and L-Cysteine to Taurine by the Enzyme Systems of Liver Cells by A. V. Soboleva; A. A. Krasnoshtanova; I. A. Krylov (pp. 236-240).
The kinetics of the conversion of the sulfur-containing amino acids L-cystine and L-cysteine to taurin by the enzyme system of cattle liver cells was studied and a mathematical model was developed. It was shown that the conversions of L-cystine and L-cysteine obeyed the Michaelis–Menten equations of serial–sequential conversions with regard to inhibition by the final product and inactivation. The yield of taurin under the optimized conditions of L-cystine and L-cysteine conversion (temperature, 40°C; pH 1.5 and 3.0, respectively; and the addition of enzyme preparations in five equal portions at 2-h intervals) was in the range of 80–85% of the substrate weight.
Cloning and Expression of the Vitreoscilla Hemoglobin Gene in Enterobacter Aerogenes: Effect on Cell Growth and Oxygen Uptake by Sebnem O. Erenler; Salih Gencer; Hikmet Geckil; Benjamin C. Stark; Dale A. Webster (pp. 241-248).
The hemoglobins found in unicellular organisms show a great deal of chemical reactivity, protecting cells against oxidative stress, and hence have been implicated in a wider variety of potential functions than those traditionally associated with animal and plant hemoglobins. There are well-documented studies showing that bacteria expressing Vitreoscilla hemoglobin (VHb), the first prokaryotic hemoglobin characterized, have better growth and oxygen uptake rates than their VHb counterparts. Here, the expression of VHb, its effect on the growth and antioxidant enzyme status of cells under different culture conditions was studied by cloning the complete regulatory and coding sequences (vgb) for VHb in Enterobacter aerogenes. Contrary to what has been reported for Escherichia coli, the expression of vgb in E.aerogenes decreased several fold under 10% of atmospheric oxygen (≈2% oxygen) and its growth was not greatly improved by the presence of VHb. Measured either as viable cells or total cell mass, untransformed E. aerogenes grew better than the recombinant strains. At the late exponential phase, however, the vgb-bearing strain was determined to have a higher cell number and total cell mass than the strain bearing only the plasmid vector with no vgb insert. The VHb expressing strain also had an oxygen uptake rate several fold higher than its counterparts. Given that oxidative stress may occur upon elevated oxygen exposure and be balanced by the action of antioxi-dative compounds, the level of antioxidative response of E. aerogenes expressing VHb was also studied. The VHb expressing strain had substantially (1.5–2.6-fold) higher catalase activity than strains not expressing VHb. Both VHb+ and VHb- strains, however, showed similar levels of superoxide dismutase activity. The activity of both enzymes was also growth phase dependent. Stationary phase cells of all strains showed 2–5-fold higher activity for these enzymes than cells at the exponential phase.
Study of a Ralstonia eutropha Culture Producing Polyhydroxyalkanoates on Products of Coal Processing by T. G. Volova; N. A. Voinov (pp. 249-252).
Kinetic indices of growth, polyhydroxyalkanoate (PHA) accumulation, and gas exchange were studied in a culture of the carbon monoxide-resistant hydrogen strain Ralstonia eutropha B-5786 grown on a gaseous substrate (GS) obtained by lignite gasification. The GS was shown to be suitable for PHA production. To increase the degree of GS consumption, various modes of gas supply to the culture were tested. Based on the results, an algorithm was developed for calculating and controlling gas-exchange parameters in the PHA-accumulating culture of Ralstonia eutropha, grown on a new GS allowing high polymer yields (up to 75%) and degrees of substrate utilization (up to 90%).
Antibacterial Effects of Water-Soluble Low-Molecular-Weight Chitosans on Different Microorganisms by D. V. Gerasimenko; I. D. Avdienko; G. E. Bannikova; O. Yu. Zueva; V. P. Varlamov (pp. 253-257).
Low-molecular-weight chitosans with a viscosity-average molecular weight (Mν) of 5 to 27 kDa and an equal degree of deacetylation (DD, 85%) were highly active against Pseudomonas aureofaciens, Enterobacter agglomerans, Bacillus subtilis, and Bifidobacterium bifidum791, causing death in 80 to 100% of cells. An exception to this tendency was Escherichia coli, for which the rate of cell death induced by the 5-kDa chitosan, was 38%. The antibacterial effect was manifested as early as 10 min after the incubation of 12-kDa chitosan with B. subtilis or E. coli cells. Candida krusei was almost insensitive to the above crab chitosans. However, Candida krusei was highly sensitive to chitosans with Mν 5, 6, 12, 15.7, and 27 kDa: the minimum inhibitory concentration (MIC) varied from 0.06 to 0.005%. Chitosans with Mν 5, 12, and 15.7 kDa exerted an antibacterial effect on Staphylococcus aureus. Chitosans with Mν 5, 15.7, and 27 kDa had no effect on Bifidobacterium bifidum ATCC 14893. The antibacterial effect of the 4-kDa chitosan on E. coli and B. bifidum 791 increased with DD in the range 55–85%.
Degradation of 2,4-Dinitrophenol by Free and Immobilized Cells of Rhodococcus erythropolis HL PM-1 by A. E. Kitova; T. N. Kuvichkina; A. Yu. Arinbasarova; A. N. Reshetilov (pp. 258-261).
The degradation of 2,4-dinitrophenol (2,4-DNP) by Rhodococcus erythropolis HL PM-1 was studied. The enzymes involved in 2,4-DNP degradation were inducible, and their resynthesis took place during the process. Cell immobilization by embedding into agar gels decreased the degrader activity. The maximum rates of 2,4-DNP degradation by free and immobilized cells were 10.0 and 5.4 nmol/min per mg cells, respectively. The concentration dependence of 2,4-DNP degradation was typical of substrate inhibition kinetics. The immobilized cells were used in a model reactor designed for 2,4-DNP biodegradation. Its maximum capacity was 0.45 nmol/min per mg cells at a volumetric flow rate of 20 h–1. The reactor operated for 14 days without losing capacity; its half-life equaled 16 days.
Low-Temperature Microbial Degradation of Oil Products Differing in the Extent of Condensation by N. I. Belousova; A. N. Shkidchenko (pp. 262-265).
Out of the 30 strains capable of oil degradation at 4–6°C, four were selected by their ability to degrade 40% of the oil substrate present in the growth medium: Rhodococcus spp. DS-07 and DS-21 and Pseudomonas spp. DS-09 and DS-22. We studied the activity of these strains as degraders of oil products of various condensation degrees (crude oil, masut, petroleum oils, benzene resins and ethanol–benzene resins) at 4–6°C. The maximum degrees of degradation of masut and ethanol–benzene resins were observed in Pseudomonas spp. DS-22 (17.2% and 5.2%, respectively). The maximum degradation of petroleum oils and benzene resins was observed in Rhodococcus spp. DS-07 (40% and 16.6%, respectively). These strains provide a basis for developing biodegrader preparations applicable to the bioremediation of oil-polluted sites under the conditions of a cold climate.
Intensification of Microbial Degradation of Crude Oil and Oil Products in the Presence of Perfluorodecalin by M. K. Bakulin; V. Yu. Zakharov; E. V. Chebotarev (pp. 266-271).
The possibility of using perfluorinated organic compounds for growing microorganisms and degrading xenobiotics has been demonstrated for the first time with perfluorodecalin (PFD), a gas-transporting component of the blood substitute Perftoran. This is particularly promising for intensifying microbial degradation of oil and oil products and the production of biodegrader biomass in synthetic mineral media. The addition of PFD to a mineral medium with crude oil and masut increased by 4.5–10.2 times the maximum concentrations and growth rates of all bacterial strains under study (Pseudomonas, Rhodococcus, and Bacillus genera). The degree of oil product consumption was increased 8.7–12.7 times.
ζ-Potential of n-Alkane Emulsion Droplets and Its Role in Substrate Transport into Yeast Cells by E. V. Komarov; P. G. Ganin (pp. 272-279).
The ζ-potentials of n-alkane droplets, formed by fatty acids, were studied in model systems of the culture liquid of yeasts (Candida maltosa) capable of utilizing n-alkanes. The value of the ζ-potential was found to depend on the droplet size. The negative ζ-potential of submicron droplets was so high that it prevented the droplets from coagulating with cells also possessing a high negative ζ-potential. The dominant role of submicron n-alkane droplets in the kinetics of yeast growth could be accounted for by the existence of a mechanism regulating the contact interactions of individual cells with the droplets followed by the uptake of the substrate.
Selection and Study of Potent Lactose-Fermenting Yeasts by W. I. Golubev; N. W. Golubev (pp. 280-284).
Whey-fermenting Kluyveromyces cultures were revealed among 105 yeast strains assimilating lactose. Eighteen strains from milk products, showing maximum potency, fermented galactose, sucrose, and raffinose, in addition to lactose. Many yeast strains fermented inulin. Most strains were resistant to cycloheximide and grew in medium containing glucose, NaCl, and ethanol at concentrations of up to 50, 11–12, and 10–12%, respectively (4°C). Three strains had mycocinogenic activity. After fermentation of whey with selected yeast strains at 30°C for 2–3 days, the ethanol concentration was 4–5%.
Degradation of the Herbicide Atrazine by the Soil Mycelial Fungus INBI 2-26 (–), a Producer of Cellobiose Dehydrogenase by V. V. Khromonygina; A. I. Saltykova; L. G. Vasil'chenko; Yu. P. Kozlov; M. L. Rabinovich (pp. 285-290).
Nonsporulating mycelial fungi producing cellobiose dehydrogenase (CDH) and isolated from soils of South Vietnam with a high residual content of dioxins are capable of growing on a solid medium in the presence of high atrazine concentrations (to 500 mg/l). At 20 and 50 mg/l atrazine, the area of fungal colonies was 1.5–1.2-fold larger, respectively, than the control colonies of the same age, whereas development of the colonies at 500 mg/l atrazine was delayed by 5 days, compared with controls grown in the absence of atrazine. Surface cultivation of the fungus on a minimal medium with glucose as a sole source of carbon and energy decreased the initial concentration of atrazine (20 mg/l) 50 times in 40 days; in addition, no pronounced sorption of atrazine by mycelium was detected. This was paralleled by an accumulation in the culture medium of extracellular CDH; atrazine increased the synthesis of this enzyme two- to threefold. Accumulation of β-glucosidase (a mycelium-associated enzyme) and cellulases preceded the formation of CDH.
Penicillium expansum, a Resident Fungal Strain of the Orbital Complex Mir, Producing Xanthocyllin X and Questiomycin A by A. G. Kozlovsky; V. P. Zhelifonova; T. V. Antipova; V. M. Adanin; N. D. Novikova; E. A. Deshevaya; B. Schlegel; H. M. Dahse; F. Gollmik; U. Grafe (pp. 291-295).
It was demonstrated that the fungus Penicillium expansum 2-7, a resident strain of the orbital complex Mir, which became dominant at the end of a long-term space flight, formed biologically active secondary metabolites (antibiotics). Using physicochemical methods these metabolites were identified as xanthocyllin X and questiomycin A. The time courses of their biosyntheses during the growth and development of the producer culture were studied. The addition of zinc to the culture medium affected both the growth of the culture and the biosyntheses of the antibiotics. The concentrations of zinc in the medium, optimum for xanthocyllin X and questiomycin A production, were 0.3 and 3.0 mg/l, respectively.
Isolation of Cell Membranes from Saccharomyces cerevisiae for Evaluation of Their Protein Composition by D. A. Aliverdieva; A. G. Malygin; L. S. Lagutina; K. F. Sholtz (pp. 296-299).
We describe a simple method for the isolation of membrane fractions from Saccharomyces cerevisiae yeasts containing a complex of plasma membranes and cell walls. The method is based on cell disruption on an INBI flow disintegrator. This device spares subcellular structures, which simplifies the isolation of cell membranes. The membrane fraction obtained by this method was suitable for studies of the protein composition of these structures by means of two-dimensional gel electrophoresis.
Hydrolysis of Chitosan in Lactic Acid by A. V. Il'ina; V. P. Varlamov (pp. 300-303).
The effects of molecular weight and the degree of acetylation on the hydrolysis of chitosan in dilute lactic acid were studied. It was demonstrated that the higher the values of both parameters, the more rapid the decreases in viscosity and the viscosity-average molecular weight of chitosan.
Determination of Polyphenolic Complex in Wines by Electrochemical Methods and Using the Enzymes Tyrosinase and Laccase by S. V. Shleev; S. A. Chekanov; O. V. Koroleva; E. V. Stepanova; Yu. A. Telegin; Z. E. Sen'kina (pp. 304-309).
Several red wines were studied to find a correlation between the physicochemical parameters characterizing the antioxidant status of wine and the total content of phenols in samples. The content of dissolved oxygen (its value varied from 0.75 to 3.28 mg/ml), pH (3.10–3.63), redox potential (–186 to –106 mV), mass concentration of free and total sulfur dioxide (10–30 and 36–200 mg/dm3, respectively), absorption spectra, and total phenol content were determined. The wines fell into two main groups—with a relatively low (1850–2050 mg/dm3) and high (2300–2900 mg/dm3) content of polyphenols. It was demonstrated that the physicochemical parameters (except for the content of sulfur dioxide) correlate with the total phenol content in the wines studied.
Effects of Treatment with a Composite Preparation (2-Chloroethylphosphonic Acid and Methacide) or Butylated Hydroxyanisole on Ethylene Release in Apples by A. S. Chernykh; E. A. Bulantseva; G. L. Shaposhnikov; A. M. Serebryanyi; M. A. Protsenko; E. G. Sal'kova (pp. 310-313).
We studied the effect of a Russian composite preparation (2-chloroethylphosphonic acid and methacide) and butylated hydroxyanisole on ethylene release in whole fruit and peel disks of two apple cultivars, Antonovka obyknovennaya (Antonovka) and Simirenko's rennet (Simirenko). Treatment with the composite preparation was followed by an increase in ethylene release from both the whole apples and peel disks. The development of microbial infection (fruit rot) in the whole apples became less pronounced after the treatment. Treatment of whole apples with the antioxidant butylated hydroxyanisole (BHA) increased the intensity of ethylene release during the first subsequent days; thereafter, ethylene release decreased and was 10–15% lower than in the control on days 10–12. In model experiments, BHA decreased ethylene release from apple peel disks below control levels as early as on the first day after treatment. Antonovka apples gave quick responses to the treatment. In the late-ripening Simirenko apples, the response persisted for a longer period. Our results suggest that treatment with physiologically active preparations affects the ethylene release, ripening, and preservation of apples in storage.
Composition and Structure of Galactomannan from the Seed of Gleditsia ferox Desf. by A. V. Egorov; N. M. Mestechkina; V. D. Shcherbukhin (pp. 314-318).
Galactomannan, a heteropolysaccharide with a molecular weight of 1660 kDa, was isolated from the seed of Gleditsia ferox Desf., introduced in Russia, with a yield of 18.9%. Its aqueous solutions were optically active ([α]D = +30.5°) and highly viscous ([η] = 1430 ml/g). An analysis of the heteropolysaccharide using chemical, enzymatic, and chromatographic procedures showed that it consists of D-mannopyranose and D-galactopyranose residues (molar ratio, 2.54 : 1). The main chain of this galactomannan consists of 1,4-β-D-mannopyranose residues, 39.2% of which are substituted at C6 with single residues of α-D-galactopyranose. The probability of occurrence of mannobiose units differentially substituted with galactose was determined by 13C-NMR data and equaled, respectively, 0.37, 0.47, and 0.16 for non-substituted Man–Man units, monosubstituted Gal(Man–Man) and (Man–Man)Gal units taken together, and for the disubstituted Gal(Man–Man)Gal units.