Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp

The psychorotrophic Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 degrees C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C10 to C21 alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5 degrees C. Mineralization of hexadecane at 5 degrees C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-dodecanol and 2-dodecanone, respectively) by solid-phase microextraction-gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis the A gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25 degrees C.     

Biodegradation of petroleum hydrocarbons by psychrotrophic Pseudomonas strains possessing both alkane (alk) and naphthalene (nah) catabolic pathways

Three hydrocarbon-degrading psychrotrophic bacteria were isolated from petroleum-contaminated Arctic soils and characterized. Two of the strains, identified as Pseudomonas spp., degraded C5 to C12 n-alkanes, toluene, and naphthalene at both 5 and 25 degrees C and possessed both the alk catabolic pathway for alkane biodegradation and the nah catabolic pathway for polynuclear aromatic hydrocarbon biodegradation. One of these strains contained both a plasmid slightly smaller than the P. oleovorans OCT plasmid, which hybridized to an alkB gene probe, and a NAH plasmid similar to NAH7, demonstrating that both catabolic pathways, located on separate plasmids, can naturally coexist in the same bacterium.     

Effects of Na+ and Mg2+ on the structures of supercoiled DNAs: comparison of simulations with experiments

Recent cryo-electron microscopy (cryo-EM) results suggest that sufficient NaCl concentration (> or approximately 0.1 M) and superhelix density (> or approximately-0.05) cause circular DNAs to adopt highly extended, tightly interwound configurations, in which the strands are laterally contiguous along almost their entire length. Millimolar levels of MgCl2 reportedly act synergistically with NaCl to produce similar conformations. However, Monte Carlo simulations with purely repulsive interduplex forces failed to reproduce such structures. In the present work, solution measurements of particular physical properties were performed both to characterize the effects of Na+ and Mg2+ on DNA structure and to provide quantitative tests of Monte Carlo simulations of circular DNAs. Supercoiled p30 delta DNAs in 10 mM Tris plus 0, 0.122, and 0.1 M NaCl, and 0.1 M NaCl plus 4 mM Mg2+ were examined by static and dynamic light scattering (LS and DLS), time-resolved fluorescence polarization anisotropy (FPA) of intercalated ethidium, and circular dichroism (CD) spectroscopy. Upon addition of 0.122 M NaCl, the radius of gyration (Rg) decreased substantially, which indicates that p30 delta adopts a more compact structure. This contradicts the cryo-EM studies, where molecular extension and Rg both increase upon adding 0.1 M NaCl. In 0.1 M NaCl, the torsion constant measured by FPA is practically invariant to superhelix density, and the plateau diffusion coefficient at large scattering vector (Dplat) is likewise nearly the same at both relaxed and native superhelix densities. Such invariance is difficult to reconcile with any transition from relaxed circles to tightly interwound structures with laterally contiguous strands. Metropolis Monte Carlo simulations were performed to generate canonically distributed sets of structures, from which average Do values and scattered intensity ratios, [symbol: see text]I (zero) [symbol: see text]/[symbol: see text] l(k) [symbol: see text], were calculated. Agreement between simulations and experiments in regard to [symbol: see text] I(O) [symbol: see text] /[symbol: see text] I(k) [symbol: see text], D(zero) and the supercoiling free energy, delta Gsc (delta l), is remarkably good for the most extensively studied p30 delta samples. The simulated structures exhibit no sign of very tight interwinding with extensive lateral contacts, but instead exhibit most probable superhelix diameters of 85 to 90 A. When 4 mM Mg2+ was added to native supercoiled p30 delta in 0.1 M NaCl, Rg decreased, D(zero) increased, and the longest internal relaxation rate (1/tau 2(zero)) increased, all of which indicate a further overall contraction of the molecular envelope. The torsion constant exhibited a slight increase that is hardly statistically significant. In this case, agreement between the simulations and experiments was only semi-quantitative for most samples investigated, although the predicted contraction was exhibited by all five samples of p30 delta and one of pBR322 DNA. The simulated structures in 0.1 M NaCl plus 4 mM Mg2+ again showed no sign of extensive lateral contacts. A plausible explanation is proposed for the highly extended, tightly interwound structures seen in cryo-EM, and explicitly tested by Monte Carlo simulations of a 1000 bp circular DNA at +25 and -50 degrees C. Structures identical to those seen in cryo-EM are in fact the equilibrium structures in the simulations at -50 degrees C, and the estimated time for equilibration (2.3 x 10(-6) second) is much smaller than the estimated time for vitrification (1 x 10(-4) second).     

Influence of corrosive environments on near-threshold fatigue crack growth in 403 stainless steel

The near-threshold fatigue crack growth behavior of 403 stainless steel has been investigated in low O₂ steam (<1 ppm), high O₂ steam (40 ppm), and boiling water with various concentrations of NaCl and Na₂SO₄ at a test frequency of 160 Hz. High O₂ steam tends to increase the crack propagation rates in the threshold region, relative to low O₂ steam. Values of threshold stress intensity range, ΔK_th, slightly increase with an increase in the concentration of NaCl in the solution. During threshold crack growth, the percentage of intergranularity decreases with a decrease inAK. Varying pH from 5.0 to 10.0 in a 0.1 gm NaCl plus 1.0 gm Na₂SO₄ per 100 ml H₂O solution does not affect the rates of near-threshold crack propagation. However, increasing the hydrazine level from 30 to 10⁷ ppb in the same salt solution enhances the resistance to crack growth while reducing the percentage of intergranular fracture to nearly zero.     

Magnitude and Variability of Biogenic Interference in Cold Regions Soils

In organic soils commonly found in cold regions, many compounds with similar characteristics are found in petroleum contamination and natural organic material (NOM). These similarities make it difficult to distinguish between natural compounds and true contamination using standard test methods. “Biogenic interference” is the term used to describe the NOM quantified as “petroleum” during a standard test for soil contamination. The inability to differentiate between biogenic interference and soil contamination is of concern because it can cause cleanup standards to be set at lower limits than the actual contamination warrants. This paper presents the results from over 200 uncontaminated soil samples that were analyzed to determine the magnitude and variability of biogenic interference in soils from cold regions. Studies were conducted to evaluate the correlation between fundamental physical∕chemical properties of soil and extractable NOM levels. Samples were also collected and analyzed to evaluate spatial (vertical and horizontal) variations in background extractable NOM at one site. A final set of samples was analyzed to determine the range of background extractable NOM levels at uncontaminated sites throughout Alaska. The results show that uncontaminated soil from across Alaska can contain several hundred to several thousand mg∕kg of extractable naturally occurring diesel and residual range organics. A high degree of variability was observed in the amount of extractable NOM at different sites across Alaska and within a single site.     

Anaerobic benzene biodegradation linked to nitrate reduction

Benzene oxidation to carbon dioxide linked to nitrate reduction was observed in enrichment cultures developed from soil and groundwater microcosms. Benzene biodegradation occurred concurrently with nitrate reduction at a constant ratio of 10 mol of nitrate consumed per mol of benzene degraded. Benzene biodegradation linked to nitrate reduction was associated with cell growth; however, the yield, 8.8 g (dry weight) of cells per mol of benzene, was less than 15% of the predicted yield for benzene biodegradation linked to nitrate reduction. In experiments performed with [14C]benzene, approximately 92 to 95% of the label was recovered in 14CO2, while the remaining 5 to 8% was incorporated into the nonvolatile fraction (presumably biomass), which is consistent with the low measured yield. In benzene-degrading cultures, nitrite accumulated stoichiometrically as nitrate was reduced and then was slowly reduced to nitrogen gas. When nitrate was depleted and only nitrite remained, the rate of benzene degradation decreased to almost zero. Based on electron balances, benzene biodegradation appears to be coupled more tightly to nitrate reduction to nitrite than to further reduction of nitrite to nitrogen gas.     

Comparative Study on Thermodynamical and Electrochemical Behavior of Al（88）Ni6La6 and Al（86）Ni6La6Cu2 Amorphous Alloys

Two amorphous ribbons with the compositions of Al88Ni6La6 and Al86Ni6La6Cu2 were made using the melt-spun method,and their thermal response and electrochemical behavior were studied comparatively.Differential scanning calorimetry（DSC）and electrochemical polarization measurements indicated that Al86Ni6La6Cu2 exhibited slightly higher crystallization temperature（Tx）,lower melting point（Tl）and better corrosion resistance in 0.01 mol·L-1 NaCl alkaline solution.These results demonstrated that Cu（2%）addition could slightly promote the glass forming ability,but it could greatly improve the corrosion resistance of Al88Ni6La6 alloy in 0.01 mol·L-1 NaCl alkaline solution.     

Biodegradation of Naphthalene-Contaminated Soils in Slurry Bioreactors

The effects of naphthalene concentrations and soil constituents (sand, clay, organic matter) on biodegrading naphthalene-contaminated soils using an acclimated Flavobacterium sp. were examined in continuously stirred slurry bioreactors. Soils with and without organic matter (1%) and kaolinite clay (20%) were used. Studies showed that sorption of naphthalene can be represented by the Freundlich isotherm. Among the soils investigated, clayey soil retarded the biodegradation process the most due to its desorption characteristics. Increasing the naphthalene contamination level from 500 mg∕kg to 25,000 mg∕kg doubled the biodegradation time in the slurry reactor with a soil loading of 10 g∕L. A pseudo first-order kinetic was observed for naphthalene biodegradation, and the biodegradation constant was determined to be 0.20 mg∕L∕h. A kinetic model was developed to simulate the biodegradation of naphthalene in a continuously stirred batch slurry reactor and to understand the role of solubilization (solid phase naphthalene), desorption, and biodegradation in the removal of naphthalene. Predictions using the numerical model agreed with the experimental data.     

The inhibition of Clostridium botulinum type C by other bacteria in wetland sediments

Bacteria with inhibitory activity against Clostridium botulinum type C were isolated from 32% of sediment samples (n = 1600) collected from 10 marshes in a northern California wetland over a 12 mo period. Aerobic and anaerobic bacteria with inhibitory activity were isolated from 12% and 23% of the samples, respectively. Bacteria with inhibitory activity were isolated from all 10 study sites and throughout the year. This study demonstrates that bacteria with inhibitory activity against C. botulinum type C occur naturally in wetland sediments.     

“零缺陷”管理理念在提升产品质量中的实践

"零缺陷"管理理念的基本原则可概括为:基于宗旨和目标,通过对经营各环节、各层面的全过程全方位管理,保证各环节、各层面、各要素的缺陷趋向于"零"。阐述了"零缺陷"管理理念,2007年首次引入邯钢质量管理,本着对造成不合格品付出代价的原则,凡因不满足预期质量要求造成的降级、改判、判废对其所在单位进行质量成本和奖金的双重考核,逐年降低质量损失。2011年通过成本考核和持续不断地改进,最终实现了比2010年降低损失10%的目标,为邯钢产品质量档次的提升和竞争力的增强打下了坚实的管理基础。     

Effect of the Composition of Anodic Purging Solutions on Electroosmosis

The objective of this study is to investigate the effect of the composition of anodic purging solutions on electroosmosis in an electrokinetic (EK) system. The effect of buffering capacity of anodic purging solutions on electroosmosis was first studied. With the increase of buffering capacity, soil pH and electric current increased, but the maximal cumulative electroosmostic flow (EOF) was achieved with 0.010?mol/L Na2CO3/NaHCO3 buffer. Na2CO3/NaHCO3 containing NaCl and Na2SO4, respectively, were used as anodic purging solutions to investigate the effect of cation concentration and anion type on electroosmosis. The increase of cation concentration led to the increase of soil pH and electric current but the decrease of EOF. At the same cation concentration, Na2SO4 resulted in higher electric current and greater EOF than NaCl, but similar distribution of soil pH. The present study provides useful information for the selection of purging solution in the EK remediation of contaminated soils.     

Diversity of the blocking effects of antisperm antibodies on fertilization in human and mouse

The blocking effects of complement-dependent sperm immobilizing antibodies in the sera of infertile women and monoclonal antisperm antibodies against humans and mice on fertilization were investigated. The hemizona assay (HZA) and sperm penetration assay (SPA) were used to study the inhibitory effects of sera from 22 infertile patients positive for sperm immobilizing antibodies. Use of these tests allowed us to differentiate whether the antibody blocked sperm-zona pellucida tight binding and/or sperm penetration into the ooplasm. The zona pellucida penetration assay (ZPA) was also used to study the effects of four monoclonal antibodies (mAbs) on human sperm penetration into the zona pellucida. Seven mAbs against murine spermatozoa were tested for their inhibitory effects on in-vitro fertilization (IVF) and HZA in mice. Of 22 patient sera with sperm immobilizing antibodies, 21 (95.5%) inhibited HZA attachment and penetration, whereas this did not occur in any of 13 patient sera without these antibodies. However, 19 of 22 (86.4%) patient sera with sperm immobilizing antibodies and eight of 13 (61.5%) patient sera without these antibodies inhibited the SPA. Two (2C6, 1G12) of four mAbs against human spermatozoa showed strong inhibitory effects in all the assays (HZA, ZPA and SPA). One mAb (3B10) did not inhibit HZA but blocked ZPA and SPA. Another mAb (H6-3C4) seemed to have no inhibitory effects on fertilization. Two (Vx 5 and Vx 8) of seven mAbs against murine spermatozoa inhibited IVF in mice but did not block mouse HZA. These findings suggest that antisperm antibodies block fertilization at specific stages. Some of them may inhibit sperm capacitation and thus prevent all processes of fertilization that follow. Some other antibodies may not affect capacitation and sperm binding to zona pellucida but inhibit the acrosome reaction, followed by the blocking of sperm penetration through zona pellucida and ooplasm.     

Effect of moisture and nitrogen levels on the decomposition of wheat straw in soil

Two per cent of wheat straw was mixed with samples of a slightly degraded chernozem soil, and its decomposition was studied at 10, 20, and 30 per cent moisture content of the soil with the addition of 160, 240, and 400 ppm of NH4 + -N. The overall decomposition, measured as CO2 production, and total carbon loss from the soil at 28 degrees C was enhanced by the added nitrogen at all levels of moisture in proportion to the quantity added. Maximum mineralization of the straw carbon was observed at 30 per cent moisture content but there was no significant difference between the amount of carbon mineralized at 20 and 30 per cent moisture levels. No stabilization of the substrate took place in the soil except at 240 and 400 ppm of applied nitrogen at 30 per cent moisture level towards the end of the incubation period. More straw carbon was mineralized when the soil samples were subjected to daily measurements of CO2 evolved than when CO2 measurements were made at intervals over the same period of incubation.     

Effects of Nutrient Source and Supply on Crude Oil Biodegradation in Continuous-Flow Beach Microcosms

Ammonium and nitrate were used as nitrogen sources to support microbial biodegradation of crude oil in continuous-flow beach microcosms to determine whether either nutrient was more effective in open systems, such as intertidal shorelines. No differences in the rate or extent of oil biodegradation were observed, regardless of whether these nutrients were provided continuously or intermittently. Nutrients were provided once every two weeks to intermittent-input microcosms and washed out within four to five days. In continuous-input microcosms, ammonium and nitrate were assimilated as quickly as they were provided during the first week, but both accumulated to greater than 10?mg?N/L thereafter. The sensitivity of the oil mineralization rate to nutrient input decreased rapidly as the extent of oil degradation increased, and after about two weeks the rate of oil-mineralization appeared to be independent of nutrient input. Therefore, there may be little value in maintaining a long-term supply of nutrients in contact with oil-contaminated sediments. The rates of microbial assimilation of ammonium and nitrate followed similar trends. Both compounds were assimilated more slowly as the extent of oil biodegradation increased, and the nitrate uptake rates approached zero after about two weeks. Ammonium assimilation continued at a low rate throughout the six-week experiment, but this did not appear to affect the rate of oil mineralization. Assimilation of ammonium resulted in a sharp decrease in the pH of the synthetic seawater that was pumped continuously through the microcosms, but nitrate had a much smaller effect on pH. The magnitude of the ammonium-associated pH change was never as large as was observed in previous studies involving oil biodegradation in batch reactors, however, and did not affect the oil-biodegradation rate.     

The oncofetal J28 epitope involves fucosylated O-linked oligosaccharide structures of the fetoacinar pancreatic protein

The use of an indigenous microbial consortium, pollutant-acclimated and attached to soil particles (activated soil), was studied as a bioaugmentation method for the aerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil. A 125-l completely mixed soil slurry (10% soil) bioreactor was used to produce the activated soil biomass. Results showed that the bioreactor was very effective in producing a PCP-acclimated biomass. Within 30 days, PCP-degrading bacteria increased from 10(5) cfu/g to 10(8) cfu/g soil. Mineralization of the PCP added to the reactor was demonstrated by chloride accumulation in solution. The soil-attached consortium produced in the reactor was inhibited by PCP concentrations exceeding 250 mg/l. This high level of tolerance was attributed to the beneficial effect of the soil particles. Once produced, the activated soil biomass remained active for 5 weeks at 20 degrees C and for up to 3 months when kept at 4 degrees C. The activated attached soil biomass produced in the completely mixed soil slurry bioreactor, as well as a PCP-acclimated flocculent biomass obtained from an air-lift immobilized-soil bioreactor, were used to stimulate the bioremediation of a PCP-impacted sandy soil, which had no indigenous PCP-degrading microorganisms. Bioaugmentation of this soil by the acclimated biomass resulted in a 99% reduction (from 400 mg/kg to 5 mg/kg in 130 days) in PCP concentration. The PCP degradation rates obtained with the activated soil biomass, produced either as a biomass attached to soil particles or as a flocculent biomass, were similar.     

氯化钙法分析土壤中重金属可提取态的精密度探讨

精密度是实验室进行质量控制的主要技术指标。目前,氯化钙法分析土壤中重金属可提取态的精密度控制指标尚未建立。采集制备5个水平土壤样品,分层随机抽取15瓶样品进行均匀性检验,分析结果采用单因素方差分析法评价,表明5批土壤样品均匀性良好。组织8家实验室开展了氯化钙法分析土壤中Cd、Cu、Ni、Zn等4种重金属可提取态的精密度试验,按照国标方法GB/T 6379.2—2004《测量方法与结果的准确度 第2部分:确定标准测量方法重复性与再现性的基本方法》进行统计分析,采用科克伦(Cochran)准则和格拉布斯(Grubbs)准则检验单元间试验数据精密度和平均值的一致性,评价了方法的重复性限(r)和再现性限(R)等精密度指标。其中Cd、Cu、Ni、Zn在0.143~7.69、0.40~24.7、0.32~2.55、3.09~181 mg/kg含量范围内,重复性限分别在0.013~0.32、0.04~1.4、0.02~0.11、0.18~7.8 mg/kg之间;再现性限分别在0.032~0.64、0.10~5.8、0.08~0.61、0.31~20 mg/kg之间。通过将重复性限和再现性限与其含量进行迭代回归统计分析,确定了分析方法重复性限和再现性限与含量的函数关系式,并进行了初步实验验证,为氯化钙法分析土壤中重金属可提取态的质量控制提供了科学依据,也为该标准方法的制订提供了数据支持。