新疆一号冰川土壤细菌多样性的研究

应用变性梯度凝胶电泳（DGGE）技术分离PCR扩增的16SrDNA来研究土壤微生物的多样性。直接从新疆一号冰川不同海拔高度的土壤样品中提取总DNA。用两套细菌通用引物分别扩增16SrDNA的V3和V6／V9高变区的特异性片段,PCR产物进行DGGE分析。PCR—DGGE图谱表明,PCR产物经DGGE检测到的条带清晰且分离效果好。结果表明,PCR—DGGE是一种快速研究微生物群落结构的有效方法。     

Evaluation of Microbial Biomass and Activity in Different Soils Exposed to Increasing Level of Arsenic Pollution: A Laboratory Study

Soil contamination with arsenic is a widespread phenomenon in many parts of the world and it is well known that it may affect the soil microbial community. A laboratory experiment was performed to evaluate the acute toxicity effect of different As concentrations (0, 0.1, 1.0, 10, 100, and 200 mg/kg) on soil biological parameters like microbial biomass carbon (MBC), active microbial biomass carbon (AMBC), basal soil respiration (BSR), fluorescein diacetate hydrolase activity (FDA), and dehydrogenase activity (DHA) under three different soil types (Inceptisol, Vertisol, and Entisol). Soil enzyme activities, microbial biomass, and respiration were significantly decreased by arsenic exposure. The soil metabolic quotient increased with increasing As concentration, the maximum being observed for Entisol followed by Vertisol and Inceptisol. Except for soil enzyme activities, the majority of which started to decrease after the addition of 10 mg/kg arsenic, all other parameters decreased at arsenic dose ≥0.1 mg/kg. The decrease of AMBC/MBC ratio showed that acute arsenic stress affected the active microorganisms more than the dormant component of total microbial biomass. Among the three soils studied, Vertisol was comparatively more tolerant to As exposure in terms of soil enzymes and biomass, followed by Inceptisol and Entisol. MBC has evolved as a distinct parameter in cluster analysis, while some others, such as DHA and AMBC, and FDA and BSR, appeared essentially redundant.     

Microbial Diversity in Cerrado Biome (Neotropical Savanna) Soils

The Cerrado, the largest savanna region in South America, is located in central Brazil. Cerrado physiognomies, which range from savanna grasslands to forest formations, combined with the highly weathered, acidic clay Cerrado soils form a unique ecoregion. In this study, high-throughput sequencing of ribosomal RNA genes was combined with shotgun metagenomic analysis to explore the taxonomic composition and potential functions of soil microbial communities in four different vegetation physiognomies during both dry and rainy seasons. Our results showed that changes in bacterial, archaeal, and fungal community structures in cerrado denso, cerrado sensu stricto, campo sujo, and gallery forest soils strongly correlated with seasonal patterns of soil water uptake. The relative abundance of AD3, WPS-2, Planctomycetes, Thermoprotei, and Glomeromycota typically decreased in the rainy season, whereas the relative abundance of Proteobacteria and Ascomycota increased. In addition, analysis of shotgun metagenomic data revealed a significant increase in the relative abundance of genes associated with iron acquisition and metabolism, dormancy, and sporulation during the dry season, and an increase in the relative abundance of genes related to respiration and DNA and protein metabolism during the rainy season. These gene functional categories are associated with adaptation to water stress. Our results further the understanding of how tropical savanna soil microbial communities may be influenced by vegetation covering and temporal variations in soil moisture.     

Assessment of Microbial Diversity in Saudi Springs by Culture-Dependent and Culture-Independent Methods

Culture-dependent and culture-independent methods were used to evaluate the microbial diversity in two hot springs of the Aljouf region in Saudi Arabia, including Qasr Kaff and Ain Hawas. Physicochemical characteristics of the springs were examined to establish their effect on the biodiversity of thermophilic bacteria and fungi. We employed culture-dependent techniques to study microbial diversity using four different complex media for bacteria and fungi. In addition, the direct count for algal populations from two springs was investigated. We surveyed the microbial diversity in water and sediment samples from both springs by denaturing gradient gel electrophoresis (DGGE) and clone library construction. Bacillariophycaea (18 species) was the most diverse group, followed by Cyanophyceaea. Bacterial isolates closer to the genera Bacillus spp., Geobacillus, Thermoactinomyces, and unidentified actinobacteria were recovered. Fungal isolates were related to Aspergillus, Pezizaceae, Penicillium, Acremonium, Fusarium, Chrysosporium, and Stachybotrys. Using molecular-based techniques, the results were slightly different from those obtained by culture-dependent methods, and more genera were obtained. However, most genera were uncultured microbes, particularly from bacterial communities.     

Microbial community composition and functional diversity in the rhizosphere of maize

This study investigates the small-scale stratification of bacterial community composition and functional diversity in the rhizosphere of maize. Maize seedlings were grown in a microcosm with a horizontal mesh (53 M) creating a planar root mat and rhizosphere soil. An unplanted microcosm served as control. Thin slices of soil were cut at different distances from the mesh surface (0.2–5.0 mm) and analysed for bacterial community composition by PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) of 16S rDNA and tested for activities of different enzymes involved in C, N, P and S cycling. Bacterial community composition and microbial functional diversity were affected by the presence of the maize roots. The bacterial composition showed a clear gradient up to 2.2 mm from the root surface, while no such gradient was observed in the unplanted pot. Invertase and phosphatase activities were higher in the close vicinity of maize roots (0.2–0.8 mm), whereas xylanase activity was unaffected. This study shows that the changes in bacterial community composition and functional diversity induced by roots may extend several millimetres into the soil.     

Chemical Extraction of Arsenic from Contaminated Soils in the Vicinity of Abandoned Mines and a Smelting Plant Under Subcritical Conditions

Under subcritical conditions, we studied the chemical extraction of arsenic (As) from contaminated soils that were sampled from the vicinity of abandoned mines and a smelting plant in South Korea. The total initial concentrations of As in the soil samples from the Myungbong and Cheongyang mines and the Janghang smelting plant were 298.6, 145.6, and 103.7 mg/kg, respectively. X-ray photoelectron spectroscopy analysis showed that the species of As identified in the soil was As(+V), including As₂O₅ and AsO₄ ^3? _. At 20°C, only 27.4, 26.5, and 40.1% of the total As was extracted from the Myungbong, Cheongyang, and Janghang soil samples, respectively, with 100 mM of NaOH. As the temperature was increased to 300°C, the extraction efficiencies remarkably increased. However, to achieve the complete extraction of As from the soils, 100 mM of citric acid, EDTA, or NaOH was needed at 200, 250, or 300°C. Extraction with subcritical water at 300°C resulted in incomplete extraction of As from the soils. The results of these experiments indicate that extraction mechanisms other than oxidative dissolution of As(+III) species may be responsible for the enhancement of As extraction. Our results suggest that subcritical water extraction combined with extracting reagents can effectively remediate As-contaminated soil regardless of the As species.     

Chemical Extraction of Arsenic and Heavy Metals from Contaminated Soils Under High Temperature and Pressure Conditions in Abandoned Mines in South Korea

The chemical extraction of As and heavy metals from contaminated soils, sampled from the Geopoong and Keumpoong mines in South Korea, was investigated under subcritical conditions. Soil samples from the abandoned mines were heavily contaminated with As, Cd, Cu, Pb, and Zn. The extent of metal removed from the contaminated soils by extractants varied according to the chemical forms of the metals in the soils. When temperature increased, the extraction of As increased accordingly, showing 92-100% removal with 100 mM of NaOH at 300°C. In contrast, the extraction of cationic metals by citric acid and ethylenediaminetetraacetic acid (EDTA) decreased markedly at 200–300°C because their chelating ability was decreased via decarboxylation and dehydration at high temperatures. Furthermore, the extraction of cationic metals was significantly affected by solution pH. Our results suggest that chemical extraction of cationic metals under subcritical conditions may be affected by several factors, including character of metal, type of extracting reagent, existing forms of metal in the soil, temperature, and soil pH.     

Toxicity and bioremediation of As(III) and As(V) in the green microalgae Botryococcus braunii: A laboratory study

Worldwide threats of fuel shortages in the near future and climate change because of greenhouse gas emissions are posing severe challenges and therefore it is vital to search for sustainable ways of preventing the consequences. The dual use of microalgae for phycoremediation and biomass production for sustainable biofuel production is a viable choice. Phycoremediation of As(III) and As(V) ions using microalgae was investigated in a two-staged batch reactor. Accumulation and toxicity of inorganic arsenic forms (As(III) and As(V)) to green microalgae Botryococcus braunii depend on environmental factors. Dissolved oxygen and pH cycles did not significantly differ due to the absence or presence of arsenic (either As(III) or As(V)) ions in the culture. Monod model was utilized for representing the growth kinetics of microalgae in pure media containing various concentrations of nitrate ions. Maximum specific growth rate and saturation constant were found to be 0.14788 d^?1 and 0.00105 g/L, respectively. With the increase in concentration of phosphate in growth medium, the growth of microalgae increased. Media with NaCl (1.0 g/L) and NaHCO₃ (1 g/L) resulted in higher maximum biomass concentration. Effect of coexisting ions on phycoremediation of As(III) and As(V) ions using microalgae was studied.     

Arsenic and Mercury in the Soils of an Industrial City in the Donets Basin,Ukraine

Soil and house dust collected in and around Hg mines and a processing facility in Horlivka, a mid-sized city in the Donets Basin of southeastern Ukraine, have elevated As and Hg levels. Surface soils collected at a former Hg-processing facility had up to 1300 mg kg^?1 As and 8800 mg kg^?1 Hg; 1M HCl extractions showed 74–93% of the total As, and 1–13% of the total Hg to be solubilized, suggesting differential environmental mobility between these elements. In general, lower extractability of As and Hg was seen in soil samples up to 12 km from the Hg-processing facility, and the extractable (1M HCl, synthetic precipitation, deionized water) fractions of As are greater than those for Hg, indicating that Hg is present in a more resistant form than As. The means (standard deviation) of total As and Hg in grab samples collected from playgrounds and public spaces within 12 km of the industrial facility were 64 (±38) mg kg^?1 As and 12 (±9.4) mg kg^?1 Hg; all concentrations are elevated compared to regional soils. The mean concentrations of As and Hg in dust from homes in Horlivka were 5–15 times higher than dust from homes in a control city. Estimates of possible exposure to As and Hg through inadvertent soil ingestion are provided.     

Influence of Arsenic from Anthropogenic Loaded Soils on the Mine Water Quality in the Tin District Ehrenfriedersdorf,Erzgebirge (Germany)

The central part of the tin ore deposit Ehrenfriedersdorf/Erzgebirge, which was exploited from the 13^th century to 1990, was flooded from 1994 to 1996. Since that time mine waters have flown through the gallery “Tiefer Sauberger Stolln” to the creek Wilisch in the Elbe river catchment area. The water at the mine portal shows high concentrations of arsenic and heavy metals. The average arsenic concentration is about 0.5 mg/L. Approximately two thirds of arsenic are transported dissolved. Where the mine water ascends from deeper levels, arsenic concentrations of about 0.4 mg/L were found. Here arsenic occurs predominantly particular. The mining gallery “Tiefer Sauberger Stolln” provides the unique opportunity of subsurface sampling for the identification of the arsenic sources under different hydrological conditions (normal and high water level). The sources of dissolved arsenic in the gallery part between the raise and the portal were determined and analyzed. Between these two monitoring points, many inflows of infiltration water were detected. The concentration of As in the infiltration water reaches up to 1.8 mg/L, which varies depending on the location in the gallery and the hydrological situation. The first part of the gallery was straightened, heightened and partly concreted with modern mining technique. The arsenic concentrations can decrease owing to high precipitation rates and snow melt events. The last part of the gallery was preserved due to low coverage. Here the arsenic concentrations in the infiltration waters increase with the surface water inflow. At a normal water level, 1 kg arsenic per day leaves the raise and 2.1 kg the gallery portal, which means that 50 % of the arsenic load comes from the infiltration water. At a high water level, 2.5 kg arsenic per day are transported through the raise and 8.2 kg per day through the gallery portal, which means that about 70 % of the arsenic load comes from infiltration water. The area of Ehrenfriedersdorf is characterized by a superposition of anthropogenic soil pollution over the geogenic inventory. There is a close connection between ancient soil contaminations by high amounts of water‐soluble arsenic compounds, e.g. arsenic trioxide formed by roasting the ores during ancient tin smelting, and high concentrations of dissolved arsenic in the infiltration water. The contamination of surface water and river sediments by arsenic is originating from an anthropogenic pollution of soils by ancient tailings via infiltration of water rich in arsenic into the mine gallery.     

Phytoremediation of lead (Pb) and Arsenic (As) by Melastoma malabathricum L. from Contaminated Soil in Separate Exposure

This study was conducted to investigate the uptake of lead (Pb) and arsenic (As) from contaminated soil using Melastoma malabathricum L. species. The cultivated plants were exposed to As and Pb in separate soils for an observation period of 70 days. From the results of the analysis, M. malabathricum accumulated relatively high range of As concentration in its roots, up to a maximum of 2800 mg/kg. The highest accumulation of As in stems and leaves was 570 mg/kg of plant. For Pb treatment, the highest concentration (13,800 mg/kg) was accumulated in the roots of plants. The maximum accumulation in stems was 880 mg/kg while maximum accumulation in leaves was 2,200 mg/kg. Only small amounts of Pb were translocated from roots to above ground plant parts (TF < 1). However, a wider range of TF values (0.01–23) for As treated plants proved that the translocation of As from root to above ground parts was greater. However, the high capacity of roots to take up Pb and As (BF > 1) is indicative this plants is a good bioaccumulator for these metals. Therefore, phytostabilisation is the mechanism at work in M. malabathricum's uptake of Pb, while phytoextraction is the dominant mechanism with As.     

Risk Element (As,Cd, Cu,Pb, and Zn) Contamination of Soils and Edible Vegetables in the Vicinity of Guixi Smelter,South China

Risk element (As, Cd, Cu, Pb, and Zn) contamination in soils and in two edible vegetables (Solanum melongena L. and Capsicum annum L.) was investigated in the vicinity of Guixi Smelter, South China. Soil As concentrations averaged 23.9 mg/kg. Sites near the smelter tailings recorded the highest levels of As and heavy metals in soils. The concentration order of heavy metals in soils was Cd < Pb < Zn < Cu. Cu and Cd in soils were abundant in the exchangeable and bound to carbonate fraction, while Pb and Zn were in the residual fraction, limiting their potential toxicity as pollutants. The proportions of the metals in the mobile fraction followed the order Pb < Zn < Cu < Cd. In Solanum melongena L. and Capsicum annum L., Zn concentration was the highest, followed by Cu, Cd, and Pb, different from that in soils and in the mobile fraction. Concentrations of heavy metals in the labile fractions in soils and in vegetables presented significant correlation (p < 0.05). Both of the two vegetables are not the Cu and Zn accumulators. As for Cd and As, Capsicum annum L. poses a higher risk to animal and human health than Solanum melongena L., with soil-plant transfer coefficients more than three. Root-stem is the main barrier for most of the heavy metals and As in the two vegetables, resulting in higher metal concentrations in roots relative to other plant tissues. The low stem-fruit transfer coefficients for Zn in Solanum melongena L. and for Pb in Capsicum annum L. suggested that very few of them could reach the fruits.     

Microbial Biomass, N Mineralization and Nitrification, Enzyme Activities, and Microbial Community Diversity in Tea Orchard Soils

Understanding the chronological changes in soil microbial and biochemical properties of tea orchard ecosystems after wasteland has been reclaimed is important from ecological, environmental, and management perspectives. In this study, we determined microbial biomass, net N mineralization, and nitrification, enzyme (invertase, urease, proteinase, and acid phosphatase) activities, microbial community diversity assessed by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA polymerase chain reaction (PCR) products, and related ecological factors in three tea orchard systems (8-, 50-, and 90-year-old tea orchards), adjacent wasteland and 90-year-old forest. Soil microbial biomass C (C_mic) and activity, i.e., soil basal respiration (R_mic), microbial biomass C as a percent of soil organic C (C_mic/C_org), N mineralization, invertase, urease, proteinase, and acid phosphatase, significantly increased after wasteland was reclaimed; however, with the succeeding development of tea orchard ecosystems, a decreasing trend from the 50- to 90-year-old tea orchard became apparent. Soil net nitrification showed an increasing trend from the 8- to 50-year-old tea orchard and then a decreasing trend from the 50- to 90-year-old tea orchard, and was significantly higher in the tea orchards compared to the wasteland and forest. Urea application significantly stimulated soil net nitrification, indicating nitrogen fertilizer application may be an important factor leading to high-nitrification rates in tea orchard soils. The Shannon’s diversity index (H) and richness (S) based on DGGE profiles of 16S rRNA genes were obviously lower in all three tea orchards than those in the wasteland; nevertheless, they were significantly higher in all three tea orchards than those in the forest. As for the three tea orchard soils, comparatively higher community diversity was found in the 50-year-old tea orchard.     

Microbial Indicators in Mine Soils (S. Domingos Mine,Portugal)

The risk assessment process planned for the S. Domingos mine, an abandoned cupric pyrite mine (Southeast Portugal), established as a task the assessment of soil microbial parameters to evaluate the long-term effects of heavy-metal contamination on the microbial community activity and subsequently on some important soil functions (e.g. nutrients cycling, decomposition of organic matter). Total metal contents as well as physical and chemical parameters (e.g. organic matter, moisture, pH and conductivity) were measured. In the study area, the levels of As, Cd, Cr, Cu, Ni and Pb were above soil quality criteria defined by some European countries. Nevertheless, sub-areas from the mining area with high concentrations of As, Cu and Pb and low soil pH levels were separated from the rest, along the first axis of a principal component analysis (PCA). The most sensitive microbial parameters were dehydrogenase activity (DHA) and potential nitrification (POTNI), which were highly depressed in the mining area. According to the redundancy analysis (RDA) of the microbial parameters and environmental variables, and Spearman rank order correlations, pH was positively correlated with these microbial parameters (DHA: r_s = 0.733, p < 0.01; POTNI: r_s = 0.676, p < 0.01). These results suggested that the contamination with some of the most toxic elements and low pH values adversely affected the biomass and the activity of soil microorganisms in the mining area. Therefore, the results of this study provided evidence about the importance of the assessment of microbial parameters, as a tool for the evaluation of direct impacts of heavy metals in contaminated sites.     

A Microbial Arsenic Cycle in Sediments of an Acidic Mine Impoundment: Herman Pit,Clear Lake,California

The involvement of prokaryotes in the redox reactions of arsenic occurring between its +5 [arsenate; As(V)] and +3 [arsenite; As(III)] oxidation states has been well established. Most research to date has focused upon circum-neutral pH environments (e.g., freshwater or estuarine sediments) or arsenic-rich “extreme” environments like hot springs and soda lakes. In contrast, relatively little work has been conducted in acidic environments. With this in mind we conducted experiments with sediments taken from the Herman Pit, an acid mine drainage impoundment of a former mercury (cinnabar) mine. Due to the large adsorptive capacity of the abundant Fe(III)-rich minerals, we were unable to initially detect in solution either As(V) or As(III) added to the aqueous phase of live sediment slurries or autoclaved controls, although the former consumed added electron donors (i.e., lactate, acetate, hydrogen), while the latter did not. This prompted us to conduct further experiments with diluted slurries using the live materials from the first incubation as inoculum. In these experiments we observed reduction of As(V) to As(III) under anoxic conditions and reduction rates were enhanced by addition of electron donors. We also observed oxidation of As(III) to As(V) in oxic slurries as well as in anoxic slurries amended with nitrate. We noted an acid-tolerant trend for sediment slurries in the cases of As(III) oxidation (aerobic and anaerobic) as well as for anaerobic As(V) reduction. These observations indicate the presence of a viable microbial arsenic redox cycle in the sediments of this extreme environment, a result reinforced by the successful amplification of arsenic functional genes (aioA, and arrA) from these materials.     

The Remediation of Chromium (VI)-Contaminated Soils Using Microbial Fuel Cells

Chromium (VI) is a priority pollutant in soil and water and poses serious threats to the environment. Microbial fuel cells (MFCs), as a sustainable technology, have been applied to treat heavy-metal-contaminated wastewater. To study MFC application in soil remediation, red clay soil and fluvo-aquic soil were spiked with Cr(VI) and packed into a cathode chamber of MFCs, which were then operated at external resistances of 100 and 1000 Ω for 16 days, with open circuit condition as a control treatment. After the operation, the concentration of dissolved Cr(VI) in supernatant and total Cr(VI) in soil was decreased. Soil type and external resistance significantly affected the current, removal efficiency of Cr(VI), and cathode efficiency. Reducing external resistance improved the removal efficiency. The red soil generated a higher current of MFCs, but showed a lower removal efficiency and cathode efficiency than fluvo-aquic soil, implying that the red soil may contain more electron acceptors that competed with Cr(VI) reduction reaction. Our study demonstrated that MFC-based technology has the potential to remediate Cr(VI)-contaminated soil; the efficiency varied between soil types and can be improved with high current.     

Bacterial Community Structure and Functional arrA Gene Diversity Associated with Arsenic Reduction and Release in an Industrially Contaminated Soil

This study aimed at evaluating potential arsenic (As) mobility in an industrially contaminated soil (64 mg/kg of As) of the Meuse River basin, and at identifying key bacterial groups that drive soil As dynamics. Both speciation and release of As from this soil was followed under anaerobic conditions using a laboratory batch experiment. In the presence of exogenous carbon sources, As^V initially present in the soil matrix and/or adsorbed on synthetic hydrous ferric oxides were solubilized and mainly reduced to As^III by indigenous soil microflora. After a 1-month incubation period in these biotic conditions, As^III accounted for 80–85% of the total dissolved As and more than 60% of the solid-phase As. Bacterial community structure (i.e., 16S rDNA-based capillary electrophoresis single-strand conformation polymorphism profiles) changed with incubation time and As amendment. The detection of distantly related arsenate respiratory reductase genes (arrA), as functional markers of As^V respirers, indicates that novel dissimilatory As^V-reducing bacteria may be involved in As biotransformation and mobility in anoxic soils. Since As and iron were concomitantly released, a crucial role of indirect As-mobilizing bacteria on As behavior was also revealed. Our results show that the majority of As within the soil matrix was bioavailable and bioaccessible for heterotrophic As^V reduction to As^III, which may increase As toxicity and mobility in the contaminated soils.     

Removal of Cadmium from Contaminated Soils by Multiple Washing with Iron (III) Chloride

In the present study, three concentrations of FeCl₃ were applied to the Cd-contaminated soils at two solid-to-solution ratios, and 1–3 washes were applied. The Cd removal percentages increased with the number of washes. An optimal treatment for removing Cd from the soil was a solid-to-solution ratio of 1/2 using 45 mM FeCl₃ and three washes. However, the application of FeCl₃ decreased the soil pH values, increased the soil electrical conductivity, and also changed the exchangeable concentrations of cations. These changes negatively influenced the germination percentage of pak choi (Brassica campestris L. ssp. chinensis) compared with control soils.     

微生物氧化As(III)和Sb(III)的研究进展

砷(Arsenic,As)和锑(Antimony,Sb)属于同族元素,具有相似的化学性质,是公认的有毒类金属(metalloid),广泛存在于自然界中。随着人类的发展,环境中砷和锑的污染日益严重,类金属污染环境的修复已经刻不容缓。现已表明,自然界中的微生物在砷和锑的生物地球化学循环中发挥着重要的作用,尤其是微生物的氧化作用,可以将毒性较强的亚砷酸盐[Arsenite,As(III)]和亚锑酸盐[Antimonite,Sb(III)]氧化为毒性较低的砷酸盐[Arsenate,As(V)]和锑酸盐[Antimonate,Sb(V)],被认为是一种潜在的类金属污染环境修复方法。本文就国内外对As(III)氧化菌和Sb(III)氧化菌的多样性、As(III)和Sb(III)微生物氧化调控机制和应用的研究进展进行总结,旨在为深入了解和探索微生物介导的砷和锑生物地球化学循环及污染环境的微生物修复提供参考。