Escherichia coli-catalyzed bioelectrochemical oxidation of acetate in the presence of mediators

Bioelectrocatalytic oxidation of acetate was investigated under anaerobic conditions by using Escherichia coli K-12 (IFO 3301) cells cultured on aerobic media containing poly-peptone, glucose or acetate as the sole carbon source. It was found that all E. coli cells cultured on the three media work as good catalysts of the electrochemical oxidation of acetate as well as glucose with Fe(CN)6(3-), 2,3-dimethoxy-5-methyl-1,4-benzo-quinone (Q0), 2,6-dichloro-indophenol, or 2-methyl-1,4-naphthoquinone as artificial electron acceptors (mediators). Acetate-grown E. coli cells exhibited the highest relative activity of the acetate oxidation against the glucose oxidation. On the other hand, all the artificial electron acceptors used work as inhibitors for the catalytic oxidation of acetate at increased concentrations. The inhibition phenomenon can be interpreted in terms of competitive substrate inhibition as a whole. Apparent values of Michaelis constant, catalytic constant, and inhibition constant were evaluated by amperometric methods. Q0 is an effective artificial mediator as evidenced by a large reaction rate constant between the cell and Q0 at least at low concentrations (<50 microM). However, Fe(CN)6(3-) is a promising mediator in biosensor applications because the inhibition constant is very large and it works as an electron acceptor even under aerobic conditions.     

Microcalorimetric Study of Antibacterial Activity of Salicylaldehyde Glucosamine Copper(Ⅱ) Complex on E.coli

Since Schiff base and its metal complexes are of antibacterial and anticancer bioactivity, it has been a research subject of much interest. It is reported that Cu(Ⅱ)-SG could inhibite the synthesis of O₂^- markedly and could also combine with the salmn sperm DNA. The paper repored that by using microcalorimetric method The growth meloabolism of E.coli at different temperature and reacted upon by Cu(Ⅱ)-SG. The power-time curves of E.coli reacted with Cu(Ⅲ)-SG at different temperature has been determined by LKB2277 Microcalorimetric Monitor and the multiplication rate constant k, generation time G,bacterial growth inhibition ratio I,total thermogenetic quantity Q, the heat quantity of a single bacterium. Q₀ and the heat quantity of a single bacterium per minute Q₀ have also been calculated. On the basis of k~T data, the formula Lnk~1/T has graphically obtained and activation energy Ea and pre-exponential factor A have been calculated. According to the parameters of the growth metabolism of E.coli,some linear relationships have been derived. The paper provides a discussion about the growth metabolism of E.coli reacted upon by Cu(Ⅱ)-SG at different temperature, and it is found that、and t_r can be used to characterize bacterial growth metabolism and the antibacterial activity of Cu(Ⅱ)-SG at different temperature.     

Microcalorimetric study of the effect of Benzoinum and Styrax on the growth of Escherichia coli

In this study, the effects of Benzoinum and Styrax on Escherichia coli (E. coli) growth were investigated by microcalorimetry. Using a TAM Air Isothermal Calorimeter, ampoule method, the power-time curves of E. coli growth at 37°C affected by Benzoinum and Styrax were measured. By analysing some quantitative thermokinetic parameters, such as growth rate constants k, the maximum heat-out power Pm, the time of the maximum heat-out power tm, the total heat production Qt and inhibitory ratio I, one could find that low concentrations (0-3.9 mg mL(-1)) of Benzoinum and Styrax had stimulation effects on E. coli growth, and high concentrations (7.8-125.0 mg mL(-1)) of these two drugs would inhibit the growth of the bacteria. The antibacterial effects of Benzoinum and Styrax can also be expressed as half inhibitory concentration IC50. The IC50 values for Benzoinum and Styrax are 78.5 and 88.0 mg mL(-1), respectively, which suggests that the antibacterial effect of Benzoinum on E. coli was much stronger than that of Styrax. This study provides a useful method to investigate the effects of herbal medicines on microbes. It also supplies some references for the application of Benzoinum and Styrax in clinical treatment.     

价电子平均能级连接性指数及其应用

定义价电子平均能级（δi）为：δi=(ni-1)(ni+ΣEij)0.5/(1+mi)。由δi建构分子连接性指数（mQ）,其中,0Q=Σ(δi)-0.5、1Q=Σ(δiδj)-0.5。0Q与无机物总键能ΔE、0Q2与过渡元素卤化物的ΔfHmθ、1Q0.5与碱金属卤化物晶格能U、0Q及1Q与无机氢化物pKa的相关系数分别为0.9734、0.9769、0.9906、0.9945,均优于文献方法。mQ是一种结构选择性、性质相关性俱佳的拓扑指数。     

季铵盐型金属卟啉的合成及其对大肠杆菌生长代谢的抑制作用

以5,10,15,20-四(4′-吡啶基)卟啉为原料,合成了一系列季铵盐型金属卟啉1a,1b和2a～2c.使用LKB2277热活性监测器测定了大肠杆菌在不同浓度的金属卟啉1a,1b和2a～2c作用下的产热曲线,得到了大肠杆菌生长速率常数k,最大发热功率P_max和最大发热功率的出现时间t_p,发现季铵盐型金属卟啉2c对大肠杆菌生长代谢的抑制活性明显大于其它季铵盐型金属卟啉.     

Calorimetry and potentiometry of chemical oscillations in Briggs-Rauscher reactions with simultaneous measurements of the produced oxygen volume

The Briggs-Rauscher reaction is known as a nonlinear and non-equilibrium chemical oscillation reaction. The reaction solution is composed of malonic acid as organic substrate, hydrogen peroxide and iodate in sulphuric acid as oxidizing agent, and manganese (II) as metal catalyst. The calorimetric behaviour, in terms of the total heat Q and the heat evolving rate q for each chemical oscillation, was followed with the use of a heat exchange calorimeter of the batch type assembled by the authors. Simultaneously, the concentration of iodide ions produced as the intermediate species was measured as the potential difference E by the common potentiometric cell incorporated in the calorimeter and the released oxygen volume G was also observed by a simple flowmeter. The starting point of the peak on the curve of q against time t coincided with that in the curve of E against t. The switching concentration of iodide between radical and nonradical paths was calculated from literature values of rate constants. The heat evolving period of Q coincided with the period in the radical path. The curve of Q against t also coincided with that of G against t. The total volume of released oxygen was larger than that calculated from the stoichiometric reaction formula.     

Rapid and ultrasensitive E. coli O157:H7 quantitation by combination of ligandmagnetic nanoparticles enrichment with fluorescent nanoparticles based two-color flow cytometry

A novel, fast and sensitive determination strategy for E. coli O157:H7 has been developed by combination of ligandmagnetic nanoparticles (LMNPs) enrichment with a fluorescent silica nanoparticles (FSiNPs) based two-color flow cytometry assay (LMNPs@FSiNPs-FCM). E. coli O157:H7 was first captured and enriched through the lectin concanavalin A (Con A) favored strong adhesion of E. coli O157:H7 to the mannose-conjugated magnetic nanoparticles. The enriched E. coli O157:H7 was further specially labeled with goat anti-E. coli O157:H7 antibody modified RuBpy-doped FSiNPs, and then stained with a nucleic acid dye SYBR Green I (SYBR-I). After dual-labeling with FSiNPs and SYBR-I, the enriched E. coli O157:H7 was determined using multiparameter FCM analysis. With this method, the detection sensitivity was greatly improved due to the LMNPs enrichment and the signal amplification of the FSiNPs labelling method. Furthermore, the false positives caused by aggregates of FSiNPs conjugates and nonspecific binding of FSiNPs to background debris could be significantly decreased. This assay allowed the detection of E. coli O157:H7 in PB buffer at levels as low as 7 cells mL(-1). The total assay time including E. coli O157:H7 sample enrichment and detection was less than 4 h. An artificially contaminated bottled mineral water sample with a concentration of 6 cells mL(-1) can be detected by this method. It is believed that the proposed method will find wide applications in biomedical fields demanding higher sensitive bacterial identification.     

PMMA-b-QPDMAEMA的合成及其抗菌活性

以α-溴代丙酸乙酯为引发剂,CuCl/二乙烯三胺为催化剂,采用ATRP法制得5个不同分子量的聚甲基丙烯酸甲酯-聚甲基丙烯酸二甲氨乙酯嵌段共聚物(PMMA-b-PDMAEMA, P¹~P⁵); P¹~P⁵经溴代辛烷季铵化合成了5个聚季铵盐(Q¹~Q⁵),其结构和性能经¹H NMR, FT-IR, GPC和DSC表征。结果表明：P⁴和Q⁴的玻璃化转变温度分别为109.67 ℃和117.95 ℃。采用平板活菌计数法研究了Q¹~Q⁵对金黄色葡萄球菌(S. aureus)和大肠杆菌(E. coli)的抗菌活性。结果表明：Q¹~Q⁵对S. aureus的抗菌活性优于E. coli,其MIC值分别为300 mg·L^-1, 250 mg·L^-1, 275 mg·L^-1, 225 mg·L^-1和150 mg·L^-1。     

Escherichia coli: Dominance of Red Light over Other Visible Light Sources in Establishing Viable but Nonculturable State

In this study, the effect of UV-A and different wavelengths of visible light irradiations combined with or without a photosensitizer (methylene blue, MB) on the establishment of viable but nonculturable (VBNC) state in Escherichia coli was investigated. Survival of the E. coli was investigated by measuring plate counts, respiring cell count (RCC), direct viable count (DVC) and total counts over a period of up to 72 h. The inhibition rates of various light sources in the presence or absence of MB on E. coli in seawater were ranked in the order UV-A>red light>white light>blue light>green light (from greatest to least activation). E. coli survived for 10.2, 19.0, 21.3 and 24.04 h under exposure to red, white, blue and green light and for 6.8 h under exposure to UV-A in the presence of MB according to t ₉₉ . Although the VC declined to undetectable levels in a relatively short time, the RCC showed that some cells were still capable of respiration and, therefore, are assumed to have entered the VBNC phase. This is the first time that red light has been shown to have a stronger effect on E. coli survival and VBNC than white, green and blue light in seawater environment.     

Water motion in reverse micelles studied by quasielastic neutron scattering and molecular dynamics simulations

Motion of water molecules in Aerosol OT [sodium bis(2-ethylhexyl) sulfosuccinate, AOT] reverse micelles with water content w(0) ranging from 1 to 5 has been explored both experimentally through quasielastic neutron scattering (QENS) and with molecular dynamics (MD) simulations. The experiments were performed at the energy resolution of 85 microeV over the momentum transfer (Q) range of 0.36-2.53 A(-1) on samples in which the nonpolar phase (isooctane) and the AOT alkyl chains were deuterated, thereby suppressing their contribution to the QENS signal. QENS results were analyzed via a jump-diffusion/isotropic rotation model, which fits the results reasonably well despite the fact that confinement effects are not explicitly taken into account. This analysis indicates that in reverse micelles with low-water content (w(0)=1 and 2.5) translational diffusion rate is too slow to be detected, while for w(0)=5 the diffusion coefficient is much smaller than for bulk water. Rotational diffusion coefficients obtained from this analysis increase with w(0) and are smaller than for bulk water, but rotational mobility is less drastically reduced than translational mobility. Using the Faeder/Ladanyi model [J. Phys. Chem. B 104, 1033 (2000)] of reverse micelle interior, MD simulations were performed to calculate the self-intermediate scattering function F(S)(Q,t) for water hydrogens. Comparison of the time Fourier transform of this F(S)(Q,t) with the QENS dynamic structure factor S(Q,omega), shows good agreement between the model and experiment. Separate intermediate scattering functions F(S) (R)(Q,t) and F(S) (CM)(Q,t) were determined for rotational and translational motion. Consistent with the decoupling approximation used in the analysis of QENS data, the product of F(S) (R)(Q,t) and F(S) (CM)(Q,t) is a good approximation to the total F(S)(Q,t). We find that the decay of F(S) (CM)(Q,t) is nonexponential and our analysis of the MD data indicates that this behavior is due to lower water mobility close to the interface and to confinement-induced restrictions on the range of translational displacements. Rotational relaxation also exhibits nonexponential decay. However, rotational mobility of O-H bond vectors in the interfacial region remains fairly high due to the lower density of water-water hydrogen bonds in the vicinity of the interface.     

碱性品红修饰磁性纳米粒子的制备及在分枝杆菌分离中的应用

痰或其它各种体液内结核分枝杆菌(MTB)阳性是诊断结核病(TB)的金标准.结核硬脂酸(TBSA)是鉴定分枝杆菌与其它非分枝杆菌的特征组分,可用于TB的诊断[1,2]。     

吸水膨胀弹性体在不同介质中的溶胀行为

研究了由共硫化法制得的三种吸水膨胀弹性体（ＷＳＥ）在不同介质中的溶胀行为，得出了溶胀速率方程和动力学参数，确定了不同介质对平衡溶胀度（Ｑｅ）的影响规律．     

新型金属卟啉的合成及其对大肠杆菌生长代谢的抑制作用

以5,10,15,20-四（对羟基苯基）卟啉（2）为原料,合成并表征了一系列 水溶性和非水溶性的金属卟啉。使用LKB 2277热活性监测器测定了大肠杆菌在金属 卟啉4a ～ 4f和7a ～ 7f作用下的生热曲线,得到了不同金属卟啉在不同浓度下大 肠杆菌生长代谢的生热速率常数k,最大发热功率p_(max)和最大发热功率的出现时 间t。结果发现,含有吡啶溴化盐的水溶性金属卟啉7a ～ 7f对大肠杆菌生长代谢 的抑制活性要明显大于含有酯基的金属卟啉4a ～ 4f。     

Simultaneous analyses of photoinduced electron transfer in the wild type and four single substitution isomers of the FMN binding protein from Desulfovibrio vulgaris, Miyazaki F

The mechanism of photoinduced electron transfer (PET) from the aromatic amino acids (Trp32, Tyr35 and Trp106) to the excited flavin mononucleotide (FMN) in the wild type (WT) and four single amino acid substitution isomers (E13T, E13Q, W32A and W32Y) of FMN binding protein (FBP) from the Desulfovibrio vulgaris (Miyazaki F) were simultaneously analyzed (Method A) with the Marcus-Hush (MH) theory and Kakitani-Mataga (KM) theory using ultrafast fluorescence dynamics of these proteins. In addition, the PET mechanism of the WT, E13T and E13Q FBP systems (Method B) were also analyzed with both MH and KM theories. The KM theory could describe all of the experimental fluorescence decays better than the MH theory by both Methods A and B. The PET rates were found to largely depend on the electrostatic energies between photo-products, isoalloxazine (Iso) anion and the PET donor cations, and the other ionic groups, and hence on static dielectric constants. The dielectric constant (ε(0)(DA)) around the PET donors and acceptor was separately determined from those (ε(0)(j), j = WT, E13T, E13Q, W32Y and W32A) in the domain between the Iso anion or the donor cations and the other ionic groups in the proteins. The values of ε(0)(DA) were always lower than those of ε(0)(j), which is reasonable because no amino acid exists between the PET donors and acceptor in all systems. The values of the dielectric constants ε(0)(j) (j = WT, E13T and E13Q) were similar to those obtained previously from the analysis of the crystal structures and the average lifetimes of these FBP proteins. Energy gap law in the FBP systems was examined. An excellent parabolic function of the logarithms of the PET rates was obtained against the total free energy gap. The PET in these FBP isomers mostly took place in the so-called normal region, and partly in the inverted region.     

Evaluation of blue and green absorbing proteorhodopsins as holographic materials

Transient holographic diffraction is observed for the green (GPR) and blue (BPR) absorbing proteorhodopsins (BAC31A8 and HOT75M1, respectively), as well as the GPR E108Q and BPR E110Q variants. In contrast to bacteriorhodopsin, where the metastable bR-M pair is responsible for generating diffraction, the pR and red-shifted N-like states fulfill that role in both the green and blue wild-type proteorhodopsins. The GPR E108Q and BPR E110Q variants, however, behave more similarly to their bacteriorhodopsin analogue, D96N, with diffraction arising from the PR M-state (strongly enhanced in both GPR E108Q and BPR E110Q). Of the four proteins evaluated, wild type (WT) GPR and GPR E108Q produce the highest diffraction efficiencies, etamax, at approximately 1% for a 1.7 OD sample. GPR E108Q, however, requires 1-2 orders of magnitude less laser intensity to generate eta equivalent to WT GPR and BR D96N under similar conditions (as compared to literature values). WT BPR requires lower actinic powers than GPR but diffracts only about 30% as well. BPR E110Q performs the most poorly of the four, with etamax < 0.05% for a 1.4 OD film. The Kramers-Kronig transformation and Koglenik's coupled wave theory were used to predict the dispersion spectra and diffraction efficiency for the long M-state variants. To a first approximation, the gratings formed by all samples decay upon discontinuing the 520 nm actinic beams with a time constant characteristic of the appropriate intermediate: the N-like state for WT GPR and BPR and the M-state for GPR 108Q and BPR E110Q.     

Effect of static magnetic field on growth of Escherichia coli and relative response model of series piezoelectric quartz crystal

The effect of magnetic field on the growth of bacteria was studied with the series piezoelectric quartz crystal (SPQC) sensing technique. The growth situations of Escherichia coli (E. coli) in the absence and presence of different intensities of static magnetic fields were examined and analyzed. The results showed that the growth of E. coli was inhibited due to the presence of magnetic fields. By fitting frequency shift (deltaD) versus time curves according to the frequency shift response equation of SPQC, the relationships between three kinetic growth parameters, i.e., the asymptote A, the maximum specific growth rate mu(m) and lag time lambda, and magnetic field intensity were established. Based on these results, a new response model containing the magnetic field intensity was derived as: delta(f) = 167.7 (7.25 - 7.11B)/[1 + exp[4 x 2.46e(-3.97B)/(7.25 -7.1 IB)] x (4.42 + 16.46B - t) + 2]] The kinetic parameters of bacterial growth obtained from this model are close to those obtained from the logistics popular growth model, in which the concentration of the bacteria was determined by the traditional pour plate count method.     

Reveal E. coli 2.0 method for detection of Escherichia coli O157:H7 in raw beef

Reveal E. coli 2.0 is a new lateral-flow immunodiagnostic test for detection of E. coli O157:H7 and O157:NM in raw beef trim and ground beef. Compared with the original Reveal E. coli O157:H7 assay, the new test utilizes a unique antibody combination resulting in improved test specificity. The device architecture and test procedure have also been modified, and a single enrichment protocol was developed which allows the test to be performed at any point during an enrichment period of 12 to 20 h. Results of inclusivity and exclusivity testing showed that the test is specific for E. coli serotypes O157:H7 and O157:NM, with the exception of two strains of O157:H38 and one strain of O157:H43 which produced positive reactions. In internal and independent laboratory trials comparing the Reveal 2.0 method to the U.S. Department of Agriculture-Food Safety and Inspection Service reference culture procedure for detection of E. coli O157:H7 in 65 and 375 g raw beef trim and ground beef samples, there were no statistically significant differences in method performance with the exception of a single internal trial with 375 g ground beef samples in which the Reveal method produced significantly more positive results. There were no unconfirmed positive results by the Reveal assay, for specificity of 100%. Results of ruggedness testing showed that the Reveal test produces accurate results even with substantial deviation in sample volume or device incubation time or temperature. However, addition of the promoter reagent to the test sample prior to introducing the test device is essential to proper test performance.     

Determination of fluoroquinolone residues in animal tissues using Escherichia coli as indicator organism

Three strains of Escherichia coli (ATCC 128, 10536, and 25922) and one strain of Bacillus subtilis (ATCC 3491) were compared as indicator microorganisms in microbial inhibition tests for their ability to detect fluoroquinolone residues. E. coli strains 128 and 10536 were most susceptible to fluoroquinolone residues, with detection limits of 35-50 micrograms/kg for enrofloxacin. Of the 2 strains, E. coli 10536 was slightly less susceptible. Ciprofloxacin was detected consistently by E. coli 128 at 30 micrograms/kg. Other fluoroquinolone drugs of veterinary interest detected by E. coli 128 were sarafloxacin and difloxacin at 100-250 micrograms/kg concentration. E. coli 25922 yielded 100% sensitivity in detection of enrofloxacin only at the 250 micrograms/kg concentration, and ciprofloxacin and sarafloxacin at 200 micrograms/kg. B. subtilis detected only enrofloxacin 100% of the time at 250 micrograms/kg. The E. coli strains tested were insensitive to other antibacterials commonly used in animals, with the exception of ceftiofur which was detected by E. coli 128 and 10536 at 500 micrograms/kg. The B. subtilis strain was not effective in detecting the fluoroquinolone drugs, whereas the E. coli strains were selective for the fluoroquinolones. E. coli 128 was 100% effective in detecting enrofloxacin and ciprofloxacin in spiked diaphragm homogenate samples at 50 micrograms/kg. Of the microorganisms tested, E. coli strain ATCC 128 was highly suitable as an indicator microorganism in a microbial inhibition assay for selective detection of fluoroquinolone antibacterial residues in animal tissues.     

Strain effects in electron spin resonance spectroscopy of quintet 2,6-bis(4'-nitrenophenyl)-4-phenylpyridine

Photolysis of 2,6-bis(4'-azidophenyl)-4-phenylpyridine in 2-methyltetrahydrofuran (2MTHF) glass at 7 K leads to quintet 2,6-bis(4'-nitrenophenyl)-4-phenylpyridine as a mixture of rotational isomers. The electron spin resonance (ESR) spectrum of this mixture of rotamers shows a considerable broadening of many transitions in the range of 0-5000 G and cannot be reproduced by computer simulations solely based on the tuning of the spin Hamiltonian parameters g, D(Q), and E(Q) alone or on predictions of DFT calculations. The best modeling of the experimental ESR spectrum is obtained only when the large line-broadening parameter of Γ(E(Q)) = 1200 MHz along with the spin Hamiltonian g = 2.003, D(Q) = 0.154 cm(-1), and E(Q) = 0.050 cm(-1) is used in the spectral simulations. The most accurate theoretical estimations of the magnetic parameters of the dinitrene in a 2MTHF glass are obtained from the B3LYP/6-311+G(d,p)+PBE/DZ/COSMO calculations of the spin-spin coupling parameters D(SS) and E(SS). Such calculations overestimate the E(Q) and D(Q) values of the dinitrene just by 1% and 10%, respectively, demonstrating that contributions of the spin-orbit coupling parameters D(SOC) and E(SOC) to the total D(Q) and E(Q) values are negligibly small. The research shows that ESR studies of polynuclear high-spin nitrenes, obtained by photolysis of rotational isomers of the starting azides, can only be successful if large E(Q) strain effects are taken into account in the spectral simulations.     

Chemical activity of palladium clusters: Sorption of hydrogen

Samples of Pd/SiO2 with average cluster size of palladium (d(Pd)) ranging from 1 to 10 nm were prepared by different methods, such as incipient wetness impregnation (IW), ion exchange (IE), and sol-gel (SG). The dispersion (D(Pd)) for prepared Pd/SiO2 samples varied with the method of preparation and showed a trend of IW < IE < SG. Chemical interaction between the dispersed nanopalladium and hydrogen gas was calorimetrically studied as a function of hydrogen uptake. Measured profiles of interaction energy vary with the d(Pd) of studied samples. The initial heat of hydrogen chemisorption (Q(Hi)) also steeply increases for particles with d(Pd) smaller than 2 nm.