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1.
We find that three mechanisms lead to the absorption enhancements of light in a thin-film amorphous silicon solar cell coated with a periodic array of silver nanoparticles on the rear surface according to our simulation. They are localized surface plasmon modes of the silver nanoparticles, Fabry–Pérot resonant cavity modes and waveguide effects. Each enhancing mechanism can yield a maximum absorption enhancement of over two times at the corresponding resonant wavelengths when the nanoparticles cover 20 % of the solar cell surface, and an average absorption enhancement of up to 57 % can be achieved in the AM 1.5 G solar spectrum. The absorption enhancements can also be tuned in spectrum to optimize the total absorption in a plasmonic solar cell. 相似文献
2.
Sulfur-Specific Microbial Desulfurization of Sterically Hindered Analogs of Dibenzothiophene 总被引:6,自引:6,他引:6
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Dibenzothiophenes (DBTs) bearing alkyl substitutions adjacent to the sulfur atom, such as 4,6-diethyldibenzothiophene (4,6-DEDBT), are referred to as sterically hindered with regard to access to the sulfur moiety. By using enrichment cultures with 4,6-DEDBT as the sole sulfur source, bacterial isolates which selectively remove sulfur from sterically hindered DBTs were obtained. The isolates were tentatively identified as Arthrobacter species. 4,6-DEDBT sulfone was shown to be an intermediate in the 4,6-DEDBT desulfurization pathway, and 2-hydroxy-3,3(prm1)-diethylbiphenyl (HDEBP) was identified as the sulfur-free end product. 相似文献
3.
The hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus was found to be capable of lithoautotrophic growth on medium containing molecular hydrogen, sulfate, and amorphous Fe(III) oxide. During the growth of this microorganism, amorphous Fe(III) oxide was transformed into black strongly magnetic precipitate rich in magnetite, as shown by Moessbauer studies. Experiments involving inhibition of microbial sulfate reduction and abiotic controls revealed that magnetite production resulted from chemical reactions proceeding at elevated temperatures (83°C) between molecular hydrogen, amorphous Fe(III) oxide, and sulfide formed enzymatically in the course of dissimilatory sulfate reduction. It follows that magnetite production in this system can be characterized as biologically mediated mineralization. This is the first report on magnetite formation as a result of activity of sulfate-reducing microorganisms. 相似文献
4.
Spent mycelia of Blakeslea trispora recovered from a previous fermentation enhanced carotene production by mated cultures of the same organism. Peak yields of 107 to 142 mg of carotene per 100 ml of medium were achieved in 6 days. β-Carotene constituted 92% of the total carotenoids produced. The enhancing substance was found present in an aqueous extract of the mycelium. Part of its activity was due to an organic acid fraction. Other microbial cells, molds, yeasts, and bacteria were also capable of enhancing carotene production. 相似文献
5.
Bulbous rush (Juncus bulbosus) is a pioneer species in acidic, iron-rich, coal mining lakes in the eastern part of Germany. Juncus roots are coated with iron plaques, and it has been suggested that microbial processes under the iron plaques might be supportive for Juncus plant growth. The objectives of this work were to enumerate the microbes involved in the turnover of iron and organic root exudates in the rhizoplane, to investigate the effect of oxygen and pH on the utilization of these exudates by the rhizobacteria, and to study the ability of the root-colonizing microbiota to reduce sulfate. Enumeration studies done at pH 3 demonstrated that 106 Fe(III) reducers and 107 Fe(II) oxidizers g (fresh wt root)–1 were associated with Juncus roots. When roots were incubated in goethite-containing medium without and with supplemental glucose, Fe(II) was formed at rates approximating 1.1 mmol g (fresh wt root) –1 d–1 and 3.6 mmol g (fresh wt root)–1 d–1 under anoxic conditions, respectively. These results suggest that a rapid microbially mediated cycling of iron occurs in the rhizosphere of Juncus roots under changing redox conditions. Most-probable-number estimates of aerobes and anaerobes capable of consuming root exudates at pH 3 were similar in the rhizosphere sediment and in Juncus roots, but numbers of aerobes were significantly higher than those of anaerobes. At pH 3, supplemental organic exudates were primarily subject to aerobic oxidation to CO2 and not subject to fermentation. However, at pH 4.5, root exudates were also rapidly utilized under anoxic conditions. Root-associated sulfate reduction was not observed at pH 3 to 4.5 but was observed at pH 4.9. The pH increased during all root-incubation studies both under oxic and anoxic conditions. Thus, as result of the microbial turnover of organic root exudates, pH and CO2 levels might be elevated at the root surface and favor Juncus plants to colonize acidic habitats. 相似文献
6.
Vishal Shah Shreya Shah Hirsh Shah Fred J. Rispoli Kevin T. McDonnell Selam Workeneh Ajay Karakoti Amit Kumar Sudipta Seal 《PloS one》2012,7(10)
Cerium oxide nanoparticles have found numerous applications in the biomedical industry due to their strong antioxidant properties. In the current study, we report the influence of nine different physical and chemical parameters: pH, aeration and, concentrations of MgSO4, CaCl2, KCl, natural organic matter, fructose, nanoparticles and Escherichia coli, on the antibacterial activity of dextran coated cerium oxide nanoparticles. A least-squares quadratic regression model was developed to understand the collective influence of the tested parameters on the anti-bacterial activity and subsequently a computer-based, interactive visualization tool was developed. The visualization allows us to elucidate the effect of each of the parameters in combination with other parameters, on the antibacterial activity of nanoparticles. The results indicate that the toxicity of CeO2 NPs depend on the physical and chemical environment; and in a majority of the possible combinations of the nine parameters, non-lethal to the bacteria. In fact, the cerium oxide nanoparticles can decrease the anti-bacterial activity exerted by magnesium and potassium salts. 相似文献
7.
Biodesulfurization of dibenzothiophene by microbial cells coated with magnetite nanoparticles 总被引:3,自引:0,他引:3
Microbial cells of Pseudomonas delafieldii were coated with magnetic Fe3O4 nanoparticles and then immobilized by external application of a magnetic field. Magnetic Fe3O4 nanoparticles were synthesized by a coprecipitation method followed by modification with ammonium oleate. The surface-modified Fe3O4 nanoparticles were monodispersed in an aqueous solution and did not precipitate in over 18 months. Using transmission electron microscopy (TEM), the average size of the magnetic particles was found to be in the range from 10 to 15 nm. TEM cross section analysis of the cells showed further that the Fe3O4 nanoparticles were for the most part strongly absorbed by the surfaces of the cells and coated the cells. The coated cells had distinct superparamagnetic properties. The magnetization (delta(s)) was 8.39 emu.g(-1). The coated cells not only had the same desulfurizing activity as free cells but could also be reused more than five times. Compared to cells immobilized on Celite, the cells coated with Fe3O4 nanoparticles had greater desulfurizing activity and operational stability. 相似文献
8.
Alessio Paris Alessandro Vaccari Antonino Calà Lesina Enrico Serra Lucia Calliari 《Plasmonics (Norwell, Mass.)》2012,7(3):525-534
We investigate on absorption and scattering from metal nanoparticles in view of possible applications to photovoltaic cells. The analysis, accounting for most of the parameters involved in the physical mechanism of scattering, is split into two parts. In the first part, scattering from a metallic sphere is treated analytically to investigate the dependence on sphere size, sphere metal, and surrounding medium. In the second part, scattering from a metallic particle is investigated as a function of particle shape (spheroids, hemispheres, and cylinders) via numerical simulations based on the finite-difference time-domain method. The aim of the work is to provide a systematic study on scattering and absorption by metal nanoparticles, exploring several combinations of material and geometrical parameters in order to identify those combinations that could play a key role in solar cell efficiency improvement. 相似文献
9.
Mechanism of Dimercaptosuccinic Acid Coated Superparamagnetic Iron Oxide Nanoparticles with Human Serum Albumin
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Lining Zhao Wei Song Jing Wang Yunxing Yan Jiangwei Chen Rutao Liu 《Journal of biochemical and molecular toxicology》2015,29(12):579-586
To research the mechanism of dimercaptosuccinic acid coated‐superparamagnetic iron oxide nanoparticles (SPION) with human serum albumin (HSA), the methods of spectroscopy, molecular modeling calculation, and calorimetry were used in this paper. The inner filter effect of the fluorescence intensity was corrected to obtain the accurate results. Ultraviolet–visible absorption and circular dichroism spectra reflect that SPION changed the secondary structure with a loss of α‐helix and loosened the protein skeleton of HSA; the activity of the protein was also affected by the increasing exposure of SPION. Fluorescence lifetime measurement indicates that the quenching mechanism type of this system was static quenching. The isothermal titration calorimetry measurement and molecular docking calculations prove that the predominant force of this system was the combination of Van der Waals’ force and hydrogen bonds. 相似文献
10.
Maria Ada Malvindi Valeria De Matteis Antonio Galeone Virgilio Brunetti George C. Anyfantis Athanassia Athanassiou Roberto Cingolani Pier Paolo Pompa 《PloS one》2014,9(1)
We have studied in vitro toxicity of iron oxide nanoparticles (NPs) coated with a thin silica shell (Fe3O4/SiO2 NPs) on A549 and HeLa cells. We compared bare and surface passivated Fe3O4/SiO2 NPs to evaluate the effects of the coating on the particle stability and toxicity. NPs cytotoxicity was investigated by cell viability, membrane integrity, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) assays, and their genotoxicity by comet assay. Our results show that NPs surface passivation reduces the oxidative stress and alteration of iron homeostasis and, consequently, the overall toxicity, despite bare and passivated NPs show similar cell internalization efficiency. We found that the higher toxicity of bare NPs is due to their stronger in-situ degradation, with larger intracellular release of iron ions, as compared to surface passivated NPs. Our results indicate that surface engineering of Fe3O4/SiO2 NPs plays a key role in improving particles stability in biological environments reducing both cytotoxic and genotoxic effects. 相似文献
11.
Sharonova N. V. Svirshchevskaya E. V. Popov A. A. Karpov N. V. Tikhonovskiy G. V. Zakharkiv A. Yu. Sizova S. V. Timoshenko V. Yu. Klimentov S. M. Oleinikov V. A. 《Russian Journal of Bioorganic Chemistry》2020,46(6):1198-1206
Russian Journal of Bioorganic Chemistry - Silicon and silicon-based nanoparticles (SiNP) attract scientific attention due to the biocompatibility and assimilation of silicon by body tissues.... 相似文献
12.
Claude Saint-Ruf Corinne Cordier Jérome Mégret Ivan Matic 《Applied and environmental microbiology》2010,76(5):1674-1678
We have developed a new method for accurate quantification of dead microbial cells. This technique employs the simultaneous use of fluorescent hydrazides and nucleic acid dyes. Fluorescent hydrazides allow detection of cells that cannot be detected with currently used high-affinity nucleic acid dyes. This is particularly important for nongrowing bacterial populations and for multicellular communities containing physiologically heterogeneous cell populations, such as colonies and biofilms.Many different approaches are used to assess the viability of bacterial cells. Currently, the most-used method is determination of the number of CFU, which reflects the ability of cells to reproduce. However, this method is not reliable because a fraction of live bacterial cells cannot divide under standard growth conditions (2) and because some bacteria are killed due to oxidative stress that occurs upon plating (3). Another approach detects dead cells through staining with fluorescent dyes that have high affinities for nucleic acids (RNA and DNA). Examples of this class of dye include Sytox Green (SG) (7). Cells incorporating these stains are then identified using flow cytometry or fluorescence microscopy. Discrimination between live and dead cells is based on the selective entry of dyes such as SG into dead cells, whose membrane integrity is compromised. However, the accessibility of DNA to SG staining also depends on the bacterial cell cycle stage. Cells that die during stationary phase are poorly stained by SG, probably because the DNA topology is altered (7). In addition, it is not possible to detect dead cells whose nucleic acids are degraded.In order to detect dead cells that escape detection by the methods described above, we used an Alexa Fluor hydrazide (AFH) dye. AFH dyes are low-molecular-weight, bright, photostable fluorescent molecules that are generally used as cell tracers by microinjection into eukaryotic cells. Because hydrazine components interact with carbonyl groups (aldehydes and ketones), AFH can be used for the detection of carbonylated proteins (1, 10). The quantity of carbonylated proteins, which are irreversibly damaged, increases after various lethal stresses such as oxidative stress, heat shock, and acidic stress (4). In stationary phase, bacteria also accumulate carbonylated proteins (5). As AFH cannot pass freely across the functional membranes of living cells, we hypothesized that it can be used for the detection of dead cells by tagging carbonylated proteins even when cells are devoid of nucleic acids. For the development of this method, we used Escherichia coli as a model organism.We first compared the results of staining E. coli cells killed by heat treatment with SG and Alexa Fluor 633 hydrazide (AF633H; both purchased from Invitrogen, Carlsbad, CA). Cells from 1- and 15-day-old liquid cultures were killed by incubation at 95°C for 10 min, which reduced the CFU counts in the cultures from approximately 2 × 108/ml to undetectable levels (below 10 CFU/ml). Aliquots of cells taken before and after heat treatment were stained with the two dyes and analyzed with a FACSAria cell sorter and flow cytometer (Becton Dickinson Biosciences, San Jose, CA) (Fig. (Fig.1).1). Among cells from the 1-day-old cultures, less than 1% collected before treatment and 99.5% collected after treatment were stained with the two dyes. The 15-day cultures contained large proportions of dead cells even before treatment, as indicated by a decrease in the CFU count from approximately 2 × 109/ml on day 1 to 1 × 108/ml on day 15 (a reduction of 95%). In 15-day cultures, 26 and 89% of cells before heat treatment were stained with SG and AF633H dyes, respectively. After heat treatment, CFU levels were again undetectable, and 99.9% of cells from 15-day cultures were stained with AF633H, while only 36% were stained with SG. This difference in staining of dead cells by SG and AF633H indicates that the ability of dead cells to be stained by SG decreases dramatically with cell age but that the staining of dead cells by AF633H increases with cell age. This may be due at least partly to the fact that AF633H can stain cells devoid of nucleic acids while SG cannot. Reconstruction experiments in which heat-treated and untreated cells from 1- and 15-day-old cultures were mixed in fixed ratios and stained by the two dyes gave expected values (Table (Table1),1), showing that AF633H can be used for precise quantification of dead cells. In addition, we observed that AF633H staining remained stable after cell fixation with paraformaldehyde (see Fig. S1 in the supplemental material).Open in a separate windowFIG. 1.Levels of fluorescence of heat-killed microbial cells stained by AF633H and SG are indicated by fluorescence intensity histograms for untreated microbial cells (white histograms) and heat-treated cells (brown histograms). Cells were stained with AF633H (left panels) and SG (right panels). E. coli (MG1665) cells were from 1- and 15-day-old cultures. D. radiodurans, B. subtilis, and S. cerevisiae cells were from 1-day-old liquid cultures. The presence of two peaks of fluorescence for cells stained with SG probably indicates the existence of cells with different numbers of copies of the chromosome.
Open in a separate windowaHeat-treated cells were mixed with untreated cells at different ratios, and the cell mixtures were simultaneously stained with AF633H and SG in order to estimate which of the two dyes is more reliable for the detection of dead cells. The number of stained cells was compared to the number of dead cells expected in each different mixed population. The probability that the number of stained cells corresponded to the known number of dead cells was estimated using a chi-square test. The expected number of dead cells in each population of untreated bacteria was defined as the total number of stained cells, i.e., the sum of the cells stained by SG, the cells stained by AF633H, and the cells stained by both dyes. In a 1-day culture, these groups were 0.3, 0.1, and 0.3% of the population, respectively; in a 15-day culture, they were 4, 62, and 22.5% of the population, respectively.We then examined mid-exponential-phase cultures treated with hydrogen peroxide (H2O2) (see the supplemental material). Cells were exposed to 20 mM H2O2 for 15 min in Luria-Bertani (LB) medium. The CFU count showed that 75% of cells were not capable of growing after treatment. Using flow cytometry, we observed that 45 min after the end of treatment, 77% of cells were stained by AF633H (Fig. 2C and D), which correlates very well with the CFU count. The same experiment was performed using an E. coli strain with the deletion of the gene coding for the RpoS sigma factor, which regulates a set of genes endowing the cells with resistance to various stresses, including oxidative stress (9). When rpoS-deficient cells were treated with H2O2, 100% were killed and stained by AF633H (data not shown).Open in a separate windowFIG. 2.Detection of oxidative-stress-killed E. coli cells by CLSM and flow cytometry. To visualize AF633H staining at the single-cell level and to evaluate the timing of carbonylation processes in cells after oxidative stress, aliquots of cells either exposed to 20 mM H2O2 or untreated were inoculated onto microscope cavity slides containing a solid matrix of M9 minimal medium-agarose with AF633H. The staining of cells with AF633H was monitored by CLSM using a Zeiss LSM 510 microscope for 1 h. (A) Untreated cells; (B) H2O2-treated cells; (C and D) flow cytometry analyses of AF633H-stained untreated cells and H2O2-treated cells, respectively. t, time.In order to trace the kinetics of protein carbonylation, the timing of AF633H staining of individual cells treated or not treated with H2O2 was monitored by confocal laser scanning microscopy (CLSM) (Fig. 2A and B; see also Movie S1 in the supplemental material). In the population of untreated bacteria, 1.6% of cells were stained after 1 h of incubation with AF633H. This indicates that AF633H very poorly stains healthy, undamaged cells. Between 1 and 45 min after treatment with H2O2 (with a peak after 30 min), individual cells became fluorescent. Forty-five minutes after treatment, 83% of cells were stained, and this percentage did not increase with further incubation. This result was in quantitative agreement with the CFU count, which showed that H2O2 treatment rendered 82% of cells incapable of growth.After determining that AFH accurately detects cells killed by different stress treatments, we wanted to detect cells that die without exogenous toxic compounds under standard laboratory growth conditions. Using the cell sorter, we isolated two populations from an overnight liquid culture of E. coli, those that were stained by AF633H and those that were not. We sorted single cells into wells of a 96-well plate that contained the growth medium and checked the capacities of the cells to grow. Less than 5% (standard deviation [SD], 3%) of AF633H-stained cells were capable of growing, while 96% (SD, 2.6%) of cells not stained by AF633H were capable of growing (Fig. (Fig.3A3A).Open in a separate windowFIG. 3.Analyses of dead cells from liquid cultures and aging colonies. (A) The live/dead status of cells stained with AF633H was investigated by cell sorting. Cells from an overnight culture were sorted into a 96-well plate filled with LB medium. AF633H-stained cells were sorted into the 48 wells on the right side of the microplate, while cells that were not stained with AF633H were sorted into the 48 wells on the left side of the microplate. The abilities of the sorted cells to reproduce were assessed by incubating the plate at 37°C and adding IPTG (isopropyl-β-d-thiogalactopyranoside) and X-Gal (5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside) to reveal β-galactosidase activity and facilitate visualization of the cells. (B) Percentages of cells in E. coli colonies stained by AF633H alone, by SG alone, and by both AF633H and SG. (C) Results from dual staining of the cells from a 4-day colony with the membrane potential dye DiOC2(3) and AF633H. (D to F) Three-dimensional views (obtained by CLSM) of a 7-day colony which was stained with SG (D) and stained with AF633H (E) and a merged image in which cells stained with AF633H and SG appear pink (F).In nature, bacteria are found mostly in structured communities, such as colonies and biofilms (6). Structured bacterial communities cause many problems for industry and for public health because they are highly resistant to various types of physical, chemical, and biotic stresses, including the host immune system. Dead cells in structured communities play an important role in the development and spreading of the communities (11, 13). Therefore, we tested the validity of our method for the quantification of dead cells in aging E. coli colonies. Cells from 1- and 11-day-old colonies were stained with SG and AF633H and analyzed by flow cytometry (Fig. (Fig.3B;3B; see also Fig. S2 in the supplemental material). Three populations of stained cells were observed: (i) cells stained only by AF633H, (ii) cells stained by both dyes, and (iii) cells stained only by SG. Over time, the percentages of cells in these three categories changed significantly. In 2-day-old colonies, 3% of all cells were stained, of which 10, 16, and 90% belonged to populations i, ii, and iii, respectively. In 11-day-old colonies, 75% of cells were stained. Among them, 55, 32, and 11% belonged to populations i, ii, and iii, respectively. These variously stained populations of cells may represent cells that die in different metabolic states and/or different phases of cell deterioration after death. Therefore, we conclude that without the use of AF633H, the majority of dead cells in old colonies would pass undetected.We also determined the numbers of cells within colonies which had active metabolism. We used the cyanine dye DiOC2(3) (3,3′-diethyloxacarbocyanine iodide) (12), which allows the estimation of membrane potential. In 1-day-old colonies, 93% of cells were metabolically active, while 40% of cells in 4-day-old colonies and 7% of cells in 7-day-old colonies were metabolically active (see Fig. S3 in the supplemental material). As these populations represented only fractions of the cells capable of growing according to the CFU count, we concluded that metabolically active cells coexist with the dormant cells, i.e., those that are alive but metabolically inactive. Simultaneous staining with DIOC2(3) and AF633H showed that cells stained by AF633H did not accumulate DIOC2(3) (Fig. (Fig.3C).3C). Therefore, we confirm that without the use of AF633H, the majority of dead cells in old colonies would pass undetected.We showed that SG and AF633H freely diffuse inside a bacterial colony (see the supplemental material). This allowed us to monitor death patterns by using CLSM without disruptions of the aging colony. For example, Fig. 3D to F show the spatial distribution of the dead cells in a 7-day-old colony.These results demonstrate that this method can be used for Gram-negative bacteria. To determine if the method is generally relevant to microorganisms, we assayed 1-day-old cultures of the Gram-positive bacteria Bacillus subtilis and Deinococcus radiodurans and the yeast Saccharomyces cerevisiae in which the cells were either heat inactivated or untreated. In all cases, AF633H staining clearly distinguished between live and dead populations (Fig. 1E to J), indicating that this technique can be broadly useful in microbiology. Considerable fluorescence from live D. radiodurans and B. subtilis cells stained with SG was observed. This background fluorescence is due probably to the binding of this dye to the cell surface, as reported previously by Lebaron et al. (8). The level of background fluorescence was much lower with AF633H. The shift in fluorescence intensity between live and dead cells was 2 log with AF633H, whereas it was only 1 log with SG.In conclusion, we developed a method consisting of the simultaneous use of fluorescent hydrazide and a high-affinity nucleic acid dye that allows precise quantification of dead microbial cells. Fluorescent hydrazides allow detection of cells that cannot be detected with currently used nucleic acid dyes, which may represent a large part of the biomass. 相似文献
TABLE 1.
Detection of dead E. coli cells in liquid cultures by AF633H and SG staininga% of heat-treated cells | % of SG-stained cells in: | % of AF633H-stained cells in: | % of expected dead cells in: | |||
---|---|---|---|---|---|---|
1-day culture | 15-day culture | 1-day culture | 15-day culture | 1-day culture | 15-day culture | |
0 | 0.6 | 26.3 | 0.4 | 84.7 | 0.7 | 88.5 |
25 | 27.45 | 31.6 | 26.6 | 87.1 | 25 | 91.4 |
50 | 48.3 | 29.6 | 48.1 | 92 | 50 | 94.2 |
100 | 98.75 | 36.1 | 99.7 | 99.9 | 100 | 100 |
Chi-square test result | 0.95 | 3.4 × 10−36 | 0.96 | 0.94 |
13.
The high-sulfur coal desulfurization process completed by A. ferrooxidans LY01 cells domesticated with either ferrous iron [Fe(II)] or pyrite (FeS2) was investigated in this article. The desulfurization rate for 13 d was as high as 67.8% for the LY01 cells domesticated with pyrite but was only 45.6% for the LY01 cells domesticated with Fe(II). Bacterial adsorption experiments indicated that the bacterial adsorption quantity onto the pyrite particles was similar to the desulfurization efficiency. FTIR analysis showed that chemical composition of the two cell types was similar, but the LY01 cells domesticated with pyrite had higher levels of hydrophobic aromatic R-O groups than cells domesticated with Fe(II). The amount of extracellular polymeric substances (EPS) from the pyrite-domesticated LY01 cells was 1820 μg C/1010 cells, which was five times more than the amount of EPS in the Fe(II)-domesticated cells; the EPS readily bound Fe(III) with a maximum binding capacity of 0.21 mg Fe(III) per mg C EPS. Strains of pyrite-domesticated LY01 with a high amount of Fe(III) in their EPS possess greater oxidation activity than Fe(II)-domesticated strains with fewer Fe(III). These experiments showed the importance of the substrate-specific differences in the oxidative activity of A. ferrooxidans LY01. In addition, this study provides theoretical guidance for the future optimization of the biodesulfurization process. 相似文献
14.
Marjorie S. Hong Evguenia Rainina Janet K. Grimsley Bruce E. Dale James R. Wild 《Bioremediation Journal》1998,2(2):145-157
A genetically engineered strain of Escherichia coli that expresses organophosphorus hydrolase (OPH) was immobilized in a polyvinyl alcohol (PVA) cryogel to form a porous biocatalyst that successfully degrades organophosphorus (OP) neurotoxins. The impacts of both diffusion and reaction on biocatalyst efficiency were determined to enable prediction and optimization of the biocatalyst performance. The kinetic rate parameters and activation energies of pure OPH, free cell suspensions, and the immobilized cell biocatalyst were compared. Diffusion was a determining factor for paraoxon hydrolysis because of the very rapid OPH kinetics for its model substrate. Both the paraoxon diffusion through the PVA matrix and the diffusion associated with microbial transport of paraoxon were shown to impact the biocatalyst reaction. However, the enhancement in storage stability resulting from diffusional limitations provides an advantage to diffusion-limited operation. This research may serve as a guide to define the influence of diffusion in biological reaction systems. The broad substrate specificity and hydrolytic efficiency of OPH coupled with the ability to genetically engineer the enzyme for specific target OP neurotoxins enhance the suitability of OPH-based technologies for detoxification of these compounds. Cryoimmobilization provides a suitable vehicle as a cost-effective, efficient technology for bioremediation of environmental media contaminated with OP compounds. 相似文献
15.
Selective Desulfurization of Dibenzothiophene by Rhodococcus erythropolis D-1 总被引:11,自引:0,他引:11
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Yoshikazu Izumi Takashi Ohshiro Hiroshi Ogino Yoshimitsu Hine Masayuki Shimao 《Applied microbiology》1994,60(1):223-226
A dibenzothiophene (DBT)-degrading bacterium, Rhodococcus erythropolis D-1, which utilized DBT as a sole source of sulfur, was isolated from soil. DBT was metabolized to 2-hydroxybiphenyl (2-HBP) by the strain, and 2-HBP was almost stoichiometrically accumulated as the dead-end metabolite of DBT degradation. DBT degradation by this strain was shown to proceed as DBT → DBT sulfone → 2-HBP. DBT at an initial concentration of 0.125 mM was completely degraded within 2 days of cultivation. DBT at up to 2.2 mM was rapidly degraded by resting cells within only 150 min. It was thought this strain had a higher DBT-desulfurizing ability than other microorganisms reported previously. 相似文献
16.
Charlotte Petters Felix Bulcke Karsten Thiel Ulf Bickmeyer Ralf Dringen 《Neurochemical research》2014,39(2):372-383
To investigate the cellular accumulation and intracellular localization of dimercaptosuccinate-coated iron oxide nanoparticles (D-IONPs) in oligodendroglial cells, we have synthesized IONPs that contain the fluorescent dye BODIPY (BP) in their coat (BP-D-IONPs) and have investigated the potential effects of the absence or presence of this dye on the particle uptake by oligodendroglial OLN-93 cells. Fluorescent BP-D-IONPs and non-fluorescent D-IONPs had similar hydrodynamic diameters and ζ-potentials of around 60 nm and ?58 mV, respectively, and showed identical colloidal stability in physiological media with increasing particle size and positivation of the ζ-potential in presence of serum. After exposure of oligodendroglial OLN-93 cells to BP-D-IONPs or D-IONPs in the absence of serum, the specific cellular iron content increased strongly to around 1,800 nmol/mg. This strong iron accumulation was lowered for both types of IONPs by around 50 % on exposure of the cells at 4 °C and by around 90 % on incubation in presence of 10 % serum. The accumulation of both D-IONPs and BP-D-IONPs in the absence of serum was not affected by endocytosis inhibitors, whereas in the presence of serum inhibitors of clathrin-dependent endocytosis lowered the particle accumulation by around 50 %. These data demonstrate that oligodendroglial cells efficiently accumulate IONPs by an endocytotic process which is strongly affected by the temperature and the presence of serum and that BP-D-IONPs are a reliable tool to monitor by fluorescence microscopy the uptake and cellular fate of D-IONPs. 相似文献
17.
Isao Takeda Takashi Iguchi Takeshi Kawamura Sadayuki Horiguchi Shiro Hayakawa Saburo Senoh 《Bioscience, biotechnology, and biochemistry》2013,77(9):796-803
Hydrocarbon-assimilating yeasts and bacteria were isolated from soil and sewage. The optimal conditions of cell yield from liquid paraffine by a Torulopsis yeast and a Pseudomonas strain were studied. A Torulopsis yeast gave, in optimal condition, 70 percent cell yield on a weight conversion basis from light oil fraction. In a strain of Pseudomonas the additions of amino acids, Fe+ +, Mg+ + and Ca+ + ions were effective for cell production. This strain showed, in optimal condition, 80 percent cell yield (wt%) from kerosene. 相似文献
18.
利用异化金属还原菌构建含糖微生物燃料电池 总被引:14,自引:0,他引:14
环境中的一些微生物通过还原金属氧化物进行无氧呼吸,而石墨电极与金属氧化物相似,也可以作为这类微生物呼吸作用的最终电子受体,利用这类微生物构建微生物燃料电池,以糖类物质为燃料,对电池产电情况、产电原理进行研究。实验结果表明,以Rhodoferaxferrireducens为产电微生物,在外接电阻510Ω条件下,以葡萄糖为燃料,常温下产生的电流密度达158mAm2(平台电压为0.46V,电极有效接触表面积为57cm2),且循环性能良好。更换燃料为其它糖,发现微生物可以利用多种糖进行产电;通过SEM观察发现大量微生物吸附在石墨电极上,用Bradford法对运行20d后电池的细胞量进行定量,测得悬浮细胞蛋白浓度为140mgL,吸附在电极上的生物量为1180mgm2。通过数据采集分析和细菌还原实验,发现吸附在电极上的微生物对电压的产生贡献最大,具有电化学和生物学活性;悬浮细胞对产电贡献很小,不具有电化学和生物学活性。 相似文献
19.
Liesje De Schamphelaire Angela Cabezas Massimo Marzorati Michael W. Friedrich Nico Boon Willy Verstraete 《Applied and environmental microbiology》2010,76(6):2002-2008
By placing the anode of a sediment microbial fuel cell (SMFC) in the rhizosphere of a rice plant, root-excreted rhizodeposits can be microbially oxidized with concomitant current generation. Here, various molecular techniques were used to characterize the composition of bacterial and archaeal communities on such anodes, as influenced by electrical circuitry, sediment matrix, and the presence of plants. Closed-circuit anodes in potting soil were enriched with Desulfobulbus-like species, members of the family Geobacteraceae, and as yet uncultured representatives of the domain Archaea.Living plants release substantial amounts of carbon in the soil as rhizodeposits, which are to a large extent transformed into the greenhouse gas methane in wetlands (21). It was recently demonstrated (8, 33) that the rhizodeposits can be harvested by plant microbial fuel cells (plant MFCs) and transformed into electricity. In its most straightforward form, a plant MFC is an adaptation of a sediment MFC (SMFC), which has an anode buried in (planted) sediment, allowing (microbial) oxidation of reduced compounds, and a cathode in the overlying water.The roots and surrounding rhizosphere in a plant SMFC add an extra parameter to the as yet multifaceted SMFC system. In the present study, two molecular profiling techniques (denaturing gradient gel electrophoresis [DGGE] and terminal restriction fragment length polymorphism [T-RFLP]) will be applied to evaluate the effect of plant presence, support material, operation of the electrical circuit, and anode depth on the bacterial and archaeal communities associated with rice SMFC anodes. Phylogenetic analysis will give further insight in their composition. 相似文献
20.
Biodesulfurization of water-soluble coal-derived material by Rhodococcus rhodochrous IGTS8 总被引:12,自引:0,他引:12
Rhodococcus rhodochrous IGTS8 was previously isolated because of its ability to use coal as its sole source of sulfur for growth. Subsequent growth studies have revealed that IGTS8 is capable of using a variety of organosulfur compounds as sources of sulfur but not carbon. In this article, the ability of IGTS8 to selectively remove organic sulfur from water-soluble coal-derived material is investigated. The microbial removal of organic sulfur from coal requires microorganisms capable of cleaving carbon-sulfur bonds and the accessibility of these bonds to microorganisms. The use of water-soluble coal-derived material effectively overcomes the problem of accessibility and allows the ability of microorganisms to cleave carbon-sulfur bonds present in coal-derived material to be assessed directly. Three coals, two coal solubilization procedures, and two methods of biodesulfurization were examined. The results of these experiments reveal that the microbial removal of significant amounts of organic sulfur from water-soluble coal-derived material with treatment times as brief as 24 h is possible. Moreover, the carbon content and calorific value of biotreated products are largely unaffected. Biotreatment does result, however, in an increased hydrogen and nitrogen content and a decreased oxygen content of the coal-derived material. The aqueous supernatant obtained from biodesulfurization experiments does not contain sulfate, sulfite, or other forms of soluble sulfur at increased concentrations in comparison with control samples. Sulfur removed from water-soluble coal-derived material appears to be incorporated into biomass. (c) 1992 John Wiley & Sons, Inc. 相似文献