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1.
Design and application of the method for isolating magnetotactic bacteria   总被引：1，自引：0，他引：1  
A simple apparatus was designed to effectively isolate magnetotactic bacteria from soils or sediments based on their magnetotaxis. Through a series of processes including sample incubation, MTB harvesting, isolation, purification and identification, several strains of bacteria were isolated from the samples successfully. By Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray Analysis (EDXA), these bacteria were certificated to be magnetotactic bacteria. The phylogenetic relationship between the isolated magnetic strains and some known magnetotactic bacteria was inferred by the construction of phylogenetic tree based on 16SrDNA sequences. This apparatus has been proven to have the advantages of being inexpensive, simple to assemble, easy to perform and highly efficient to isolate novel magnetotactic bacteria. The research indicated that the combined approach of harvesting MTB by home-made apparatus and the method of plate colony isolation could purify and isolate magnetotactic bacteria effectively.  相似文献   

2.
Within a series of pot experiments with substrates sampled at heavily to moderately polluted sites of past metal mining activities, it was tried to influence the soil plant transfer of metals via addition of complexants, soil bacteria and perlite. Lettuce （lactuca sativa） was chosen as a universal accumulator plant. A wide range of concentrations in the samples ensures a rather general approach. The goal was to develop a strategy to enable plant growth at metal contaminated substrates for phytoremediation purposes. One contaminated mine tailing from Shiheung/Korea was treated with EDTA, NTA, citric acid, malic acid, NaCl, citrate＋NaCl, as well as compost, to provoke effects from chemical treatment. This should yield low molecular metal complexes in the soil solution and provide a carbon source to natural soil life. Other samples from Shiheung, from Okdong mine tailings, Okdong farmland, as well as from three contaminated sites from a medieval mine tailing at Oberzeiring/Styria/Austrias were treated with Cd- adapted soil bacteria, perlite, and soil bacteria and perlite, to impose of changes in microbial life directly. Fresh mine tailings are low in microbial life and plant- available nitrogen, whereas in the contaminated Austrian medieval samples, conditions have had time to adapt for more than 600 years. In the test substrates, supply with nutrient nitrogen was low, supply with nutrient phosphorus was low to adequate, and supply with potassium and sulfate was adequate. Effects of various additives on the plant yield mainly depend on the initial nutrient status. After harvest, the soils were parted in root soils and bulk soils to recognize possible differences. The lettuce plants were parted in leaves and roots. The solids were characterized by convential methods and aqua regia digestion, as well as by a Tessier-type sequential leaching procedure. The plant samples were digested with HNO3/HClO4. Basically, sample solutions were simultaneously read for 23 elements in ICP-OES in appropriate dilutions. Various treatments result in concentration shifts in root soil, bulk soil, plant roots and plant leaves. Interpretation is not easy, but physiologically active elements or contaminants are usually more involved.  相似文献   

3.
Microbial enhanced oil recovery (MEOR) utilizes microbes for enhancing the recovery by several mechanisms, among which the most studied are the following: (1) reduction of oil-water interfacial tension (IFT) by the produced biosurfactant and (2) selective plugging by microbes and metabolic products. One of the ways of bacterial survival and propagation under harsh reservoir conditions is formation of spores. A model has been developed that accounts for bacterial growth, substrate consumption, surfactant production, attachment/filtering out, sporulation, and reactivation. Application of spore-forming bacteria is an advantageous novelty of the present approach. The mathematical setup is a set of 1D transport equations involving reactions and attachment. Characteristic sigmoidal curves are used to describe sporulation and reactivation in response to substrate concentrations. The role of surfactant is modification of the relative permeabilities by decreasing the interfacial tension. Attachment of bacteria reduces the pore space available for flow, i.e., the effective porosity and permeability. Clogging of specific areas may occur. An extensive study of the MEOR on the basis of the developed model has resulted in the following conclusions. In order to obtain sufficient local concentrations of surfactant, substantial amounts of substrate should be supplied; however, massive growth of bacteria increases the risk for clogging at the well inlet areas, causing injectivity loss. In such areas, starvation may cause sporulation, reducing the risk of clogging. Substrate released during sporulation can be utilized by attached vegetative bacteria and they will continue growing and producing surfactant, which prolongs the effect of the injected substrate. The simulation scenarios show that application of the spore-forming bacteria gives a higher total production of surfactant and the reduced risk of clogging, leading to an increased period of production and a higher oil recovery.  相似文献   

4.
Microbial remediation potential to crude oil-contaminated soils in the Yellow River delta was assessed. Hydrocarbons degradaters were isolated from the soil samples obtained from the Yellow River delta. A selected mixed microbial consortium （MYRD-1） and two individual isolates （YRD-3 and YRD-4） were further tested for optimal performance and degradation of different hydrocarbons. The results demonstrated that the optimal crude oil biodegradation conditions for the mixed microbial consortium were at temperature of 28 ℃, salt concentration of 15‰, and pH of 8, and the optimal C/N/P ratio was found to be 70 ： 3 ： 1. Isolate YRD-3 could only use n-alkanes （C8, C12 and C16） as the sole source of carbon and YRD-4 could transform only naphthalene and phenanthrene. The optimal performance conditions for both isolates were at salt concentration of 20‰, and pH of 7, and C/N/P ratio of 80 ： 5 ： 1, but the temperature for YRD-3 was 24 ℃ and 28 ℃ for YRD-4. Capacity to transform hydrocarbons for the mixed microbial consortium and both isolates could be improved in a liquid medium supplemented using a mixture of alkanes and/or aromatic hydrocarbons （naphthalene and phenanthrene）, but the transformation of different substrates by MYRD-1 was higher than both isolates, showing the importance of mixed bacteria （microbial community） in hydrocarbon degradation.  相似文献   

5.
The rapid kinetics of microbial U （Ⅵ） reduction and low solubility of uraninite make this process a promising strategy for removing uranium from groundwater and preventing its further migration. Nevertheless, some environmental factors that can influence U（Ⅵ） bioreduction, such as pH, the concentration of coexistent anions（sulfate, nitrate） and toxicity of heavy metal cations[Cu（ Ⅱ ）, Zn（ Ⅱ ）, etc], are not well defined. In this paper, anaerobic batch experiments were performed to evaluate their effects on the enzymatic reduction of U （Ⅵ） by mixed cultures of sulfate-reducing bacteria （SRB）. Kinetics investigations under variable pH conditions demonstrated that U （Ⅵ） was mainly reduced during the first 48h. The yield of this bacterial reduction depended strongly on the pH and increased from 4.3% to 99.4% when the pH was raised from 2.0 to 6.0. No inhibition of U （Ⅵ） bioreduction occurred and the formation Of uraninite was concurrent with the precipitation of metal sulfide （ZnS/CuS） at an initial concentration of 20 mg/L Zn （ Ⅱ ） or 10 mg/L Cu （ Ⅱ ）. But addition of 25 mg/L of Zn （ Ⅱ ） or 15 mg/L of Cu （ Ⅱ ） to the bacterial medium stopped U （Ⅵ） reduction due to their toxicities to SRB. Assessment tests for heavy metal toxicity implied that Cu （ Ⅱ ） toxicity probably proceeds by a mechanism different from that of Zn （ Ⅱ ） toxicity. The Zn （ Ⅱ ）-induced inhibition of microbial activity can be eliminated, but Cu （ Ⅱ ） toxicity can generate permanent and irreversible damage to SRB. The sulfate concentration as high as 4000 mg/L did not appreciably interfere with U （Ⅵ） reduction, however, the anion level greater than 5000 mg/L significantly slowed the rate of U （Ⅵ） reduction. Moreover, it was found that U （Ⅵ） was not reduced by H2S produced during dissimilatory sulfate reduction.  相似文献   

6.
High concentrations of arsenic and humic substances in groundwater from the southwestern coastal plain of Taiwan were well known for their probable relationships with black-foot disease. In order to realize the relationships between the concentrations of humic substances and arsenic in this area, 24 well water samples were analyzed. After filtered through 0.45 μm glass fiber membrane in the field, samples were kept in the dark at 4℃ and then separated into six fractions with varying range of molecular weight （〈0.5, 0.5-1, 1-5, 5-10, 10-50 and 〉50 k Da） by ultrafiltration apparatus （Molecular/Por Stirred Cell system） in the lab. Concentrations of humic substances were measured by fluorescence spectrometer （HITACHI F-2000, ex=370, em=445） and arsenic by FIAS-AA （Perkin Elmer AAnalyst 100, FIAS-400）. On average, only 6.2% of the total arsenic in water existed in the fraction of 〉0.5 k Da. and the others were complexed with humic substances （including humic acid and fulvic acid）. The results demonstrated a distinct positive correlation between the concentrations of humic substances and arsenic.  相似文献   

7.
The purpose of the thesis is to analyze the temporal and dimensional distribution of sulfate-reducing bacteria （SRB） groups and quantity in Lake Erhai. In April and September 2005, two sediment cores were collected from Lake Erhai. SRB groups were analyzed by PCR with six-groups primers designed according to the specific 16SrDNA sequence. FISH （fluorescence in-situ hybridization） was established with the oligonucleotide probe （SRB385） and utilized to analyze SRB quantity in the sediments. The results showed that in the sediments of Lake Erhai four SRB groups were detected except Desulfobacterium and Desulfobacter, meanwhile Desulfovibrio-Desulfomicrobium were detected only in autumn; different SRB groups had different temporal and dimensional distribution, and each group in autumn is distributed more widely than in spring; FISH used to count SRB in the sediments of fresh lake was set up successfully; the analysis of correlation between the sediment＇s depth and SRB quantity had statistical meaning （P〈0.05） . The result showed that SRB quantity showed a decreasing trend with increasing depth. Through the analysis of randomized block designed analysis of variance, the difference in SRB quantity between spring and autumn also had statistical meaning （P〈0.001）, which revealed SRB quantity in autumn was larger than in spring; the result of FISH showed that there were some SRB in the deeper sediments in which no above-mentioned six SRB groups were detected by PCR. SRB groups in the sediments of Lake Erhai were rich, and the quantities of SRB groups in autumn were larger than in spring; possibly there were uncultivable SRB groups in the sediments of Lake Erhai.  相似文献   

8.
This investigation was carried out for evaluation of indole-3-acetic acid production by bacteria under salinity and salinity–sodicity stress. A total of 298 bacteria were isolated from soils with different levels of electrical conductivity and sodium adsorption ratio. Then, ability of indole-3-acetic acid production under salinity, salinity–sodicity and l-tryptophan concentrations was analyzed. The results indicated that the ability of growth and indole-3-acetic acid production among bacteria was significantly affected by salinity, salinity–sodicity and l-tryptophan concentration. The one of the bacterial species, Arthrobacter siccitolerans, that were isolated from saline–sodic soils can adjust its indole-3-acetic acid production to different levels of salinity and salinity–sodicity stress conditions. Also, its l-TRP use efficiency under salinity–sodicity stress was 5.01% and reported as the most efficient bacterium. Seed inoculation of A. siccitolerans enhanced wheat aerial and root dry matter under salinity–sodicity stress with respect to control by 10.03 and 15.17%, respectively. The study indicates the different effects of salinity–sodicity on indole-3-acetic acid indole-3-acetic acid production and the potential of A. siccitolerans for production of indole-3-acetic acid and enhancing growth of wheat under salinity and salinity–sodicity stress.  相似文献   

9.
Doklady Earth Sciences - This paper reports on the first U–Pb dating of zircons from dacites of the volcanic paleo-edifice of the andesite–dacite complex of the Eastern Zone of the...  相似文献   

10.
Synthetic surfactants are among the most widely used chemicals in the world （around 10 millions of tons are produced per year）, mainly as key components in detergent formulation, apart from other applications such as wetting agents or emulsifiers. Coastal ecosystems receive large quantities of these compounds and, after a relatively fast partial degradation in water, the remaining quantities end up in the sediments due to their high affinity for organic carbon in the particulate phase. We therefore focused our studies on sediments because they can be assumed to play an important environmental role acting as a sink for these contaminants. Moreover, because of their widespread use and source specificity, surfactants can usefully be employed as molecular indicators in sediments for more general contamination caused by human activities. This work deals with the vertical distribution in sediment cores of the main anionic surfactants, both linear alkylbenzene sulfonates （LAS） and alkyl ethoxysulfates （AES）, and non-ionic surfactants, including nonylphenol polyethoxylates （NPEOs） and alcohol polyethoxylates （AEOs）. In the case of LAS their degradation metabolites sulfophenyl carboxylic acids （SPCs） are also studied. The processes considered are degradation, sorption and diffusion occurring along the sedimentary column for the different homologues contained in the commercial surfactant mixtures. The most hydrophobic surfactants such as NPEOs and AEOs remain strongly attached to the particulate phase whereas polar metabolites such SPCs tend to be present in the pore water. Highest values of surfactants are found near the surface and, in most cases, there is a decrease in their concentration down the sediment core. Furthermore, the reduction in the average length of the ethoxylated chain in polyethoxylated surfactants, as well as the increase in the concentrations of SPCs at depths showing redox potential from -300 to -400 mV, suggests that surfactants may be degraded anaerobically in the sediment. In the case of LAS, these field results are compared with the data from laboratory experiments carried out in order to determine sorption capacity and anaerobic degradation.  相似文献   

11.
The first results on current movements are presented for the western part of the Dzhugdzhur–Stanovoi Terrane based on GPS geodesy of a geodynamic survey area of the Upper Amur region. Processing of the GPS data resulted in a vector field of the displacement rates of points of the geodynamic survey area with zones of intense deformations. It was concluded from a comprehensive analysis of geological–geophysical data and estimates of the displacement rates that the terrane is characterized by kinematic integrity and was subjected to a complex of tectonic factors related to the evolution of the eastern segment of Baikal Rift Zone in the area of transpression interaction of the Eurasian and Amur plates.  相似文献   

12.
In this study, five cores of the Anllóns River bed sediments were analyzed in order to evaluate the downcore and downstream variations in their chemical composition. The first step was the evaluation of the metal distribution in the bulk (<2 mm) and fine fractions (<63 μm). The analysis revealed that most of the metals followed the same trend in both fractions, although the fine fraction presented usually higher concentrations. However, the concentration of both fractions tended to equalize with increasing contamination. No general increase was observed in the metal concentrations toward the surface which could be attributed to recent anthropogenic contributions. Instead, the distributions were homogeneous or peaked at various depths downcore. The most important historical feature was observed at the mouth of the river, at 96-cm depth, corresponding to the end of the eighteenth century. Upcore increased metal concentrations in parallel with increased fine fraction occurred from this depth, which were attributed to a bridge construction and consequent changes in sediment dynamics. As the metal concentrations can be influenced by variations in texture or other sediment characteristics, the second step was to evaluate the efficiency of several normalized indexes in the assessment of the degree of contamination, by calculating the enrichment factor (EF), the geoaccumulation index (I GEO) and the pollution load index (PLI). The EFs obtained were <10, thus revealing little anthropogenic inputs to the basin. The I GEO produced higher values when compared with the EFs. Instead of absolute EF or I GEO absolute values, the use of cumulative probability plots allowed identifying more accurately potential outliers indicating contamination. Only one population was identified for Zn and Pb, with a reduced number of outliers at the highest concentrations for Pb. As shown, a more complex plot with the outliers identified at C4 and C5. Finally, the PLI allowed determining the absence of a significant contamination in the bed sediments. The bioavailable and non-geogenic fractions contribute up to a 90% of the total concentrations in the case of As and Cu, and showed similar (dissimilar) profiles in comparison with total metals. Also, the quality guidelines were surpassed, so the high solubility of As, Zn, Pb and Ni in the sediments revealed the need to monitor the bed sediment quality of the Anllóns River.  相似文献   

13.
Doklady Earth Sciences - The influence of the temperature and moisture content of the near-surface soil layer on variations of the barodeformation interaction of the boundary layer of the...  相似文献   

14.
Doklady Earth Sciences - The influence of variations in fo-, fa-, en-, fs-, di-, an-, and ab-components in a high-Mg basaltic melt on the topology of the spinellide liquidus was analyzed using the...  相似文献   

15.
Bursting the Limits of Time by the distin- guished historian of geology Martin Rudwick is a massive, two-part book. The first part contains what he calls a synchronous history of what eventually became historical geology in western Europe between the time of de Sans- sure＇s epoch-making ascent of Mont Blanc in 1787 and the discovery of the Kirkdale hyaena cave by Buckland in the winter of 1821-1822,  相似文献   

16.
Uranium processing and mining activities that generate many contaminants, such as high concentrations of U （VI）, sulfate and heavy metals （Zn, Cu, Ni, etc）, may pose a serious threat to the groundwater resources. In recent years, considerable research has been conducted respectively on two kinds of permeable reactive barriers （PRB）, including zerovalent iron （ZVI） and sulfate reducing bacteria （SRB）, for in-situ removal of these pollutants from groundwater. However, little investigation has been carried out on the potential benefits of bioaugmenting ZVI barriers to enhance the elimination of the pollutants by combining ZVI with SRB systems. The main goal of this study was to conduct batch and column experiments to determine whether the combination of SRB and ZVI can function synergistically and accelerate the rate of pollutant removal. The results of anaerobic batch experiments demonstrated that although the integrated ZVI/PRB system itself has no ability to reduce and remove sulfate directly, SRB can utilize hydrogen gas produced during the slow process of ZVI corrosion as an electron donor to raise biomass yields significantly and accelerate reductive sulfate removal. In particular, ferrous cations produced as the byproduct of ZVI corrosion process reacted with hydrogen sulfide from sulfate reduction and formed iron-bearing sulfide precipitates, which can stimulate the growth of SRB and promote sulfate removal activity by eliminating the biotoxicity of hydrogen sulfide. It was also shown that secondary mineral products （pyrite/ferrous sulfide） formed as a consequence of microbial sulfate reduction and ZVI corrosion process can enhance the microbial precipitation of soluble U （VI） as insoluble uraninite（uranium dioxide）.  相似文献   

17.
陶正章 《中国地球化学学报》1991,10(3):288-293,T003
The carat is the unit of weight for diamonds and other gemstones.It corresponds to the average weight of the seeds of a leguminous tree.What kind of tree is this?We have studied the samples from Ethiopia,Egypt,Cyprus and the United States.The tree is neither“Kuara“nor“Locust“（Robina pseudoacacia Linn.）,but rather Carob(Ceratonia Siliqua).In Ethiopia,as called by local inhabitants,“Kuara“is a species of Erythrina-E.brucei rather than E.abyssinica.As might be expected,using the seeds as a means of weighing an extremely valuable commodity is not very scientific.Before 1907,at various times and in various countries,there were at least twenty-three stan-dards for the carat ranging from 187.00mg to 215.990mg.The metric carat equal to 200mg was proposed in Paris in 1907.It was adopted in the United States on July1,1913 and now is the world-accepted standard.But in reality,the standard of the carat is still confused with respect to its usage throughout the world .This is why the author reiterates that the standard of the car-at should be integrated with the metric system.  相似文献   

18.
The catastrophic Shikotan earthquake of October 4 (5), 1994, occurred in the Pacific Ocean. Its focus was located 80 km eastward of Shikotan Island. The stress state of the Earth’s crust in this area was estimated by the method of the cataclastic analysis of the whole range of the earthquake mechanisms. The performed reconstruction of the parameters of the current stress state of the Earth’s crust and the upper mantle in the area of the Southern Kuril Islands made it possible to establish that this area is characterized, on the one hand, by the presence of extensive areas of steady behavior of the stress tensor parameters and, on the other hand, by the presence of local sections of anomalously fast changes in these parameters.  相似文献   

19.
Doklady Earth Sciences - The problems of diagnostics of the beginning of agrarian development of coniferous–broad-leaved forests in northwestern European Russia and its specificity regarding...  相似文献   

20.
This paper discusses the discrimination principles. deduction and methods for probing into the source composition of mantle-derived magma. The magmatophile (incompatible) source elements are not all optimal tracers for mantle source composition. The ratios of two strong magmatophile elements (D<1) or the ratios of two trace elements with the same D value are not controlled by the formation mode and evolution degree of a magma, but maintain the characteristics of their composition in mantle source region prior to the magma formation. The ratios are related to different mantle-crust structures and dynamics. The mantle source composition of the Emeishan Basalt series is similar to that of the South Atlantic Rio Grande Rise-Walvis Ridge Basalts and Brazil continental-margin basalts. This may indicate that these basalt series might have similar source regions and tectonic environments.  相似文献   

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