Bioremediation of copper-contaminated soils by bacteria

Although copper (Cu) is an essential micronutrient for all living organisms, it can be toxic at low concentrations. Its beneficial effects are therefore only observed for a narrow range of concentrations. Anthropogenic activities such as fungicide spraying and mining have resulted in the Cu contamination of environmental compartments (soil, water and sediment) at levels sometimes exceeding the toxicity threshold. This review focuses on the bioremediation of copper-contaminated soils. The mechanisms by which microorganisms, and in particular bacteria, can mobilize or immobilize Cu in soils are described and the corresponding bioremediation strategies—of varying levels of maturity—are addressed: (i) bioleaching as a process for the ex situ recovery of Cu from Cu-bearing solids, (ii) bioimmobilization to limit the in situ leaching of Cu into groundwater and (iii) bioaugmentation-assisted phytoextraction as an innovative process for in situ enhancement of Cu removal from soil. For each application, the specific conditions required to achieve the desired effect and the practical methods for control of the microbial processes were specified.     

Bioremediation potential of basidiomycetes isolated from compost

The potential of a consortium of three basidiomycete mycelia isolated from compost to degrade polycyclic aromatic hydrocarbons (PAH) was first evaluated using a test based on decolorization of Poly R-478 dye. When pre-grown on straw, the consortium decolorized the dye by 83% in 7 days and generated a laccase activity of 663 IU l(-1). Its ability to degrade naphthalene was investigated in soil microcosms specially suited for this volatile PAH. The kinetic study was conducted at a maximal naphthalene concentration of 500 mg kg(-1) of soil. Naphthalene concentration, CO(2) evolution and phytotoxicity (germination index, GI%) on Lepidium sativum seeds were monitored. The naphthalene concentration decreased by about 70% in three weeks in the presence of metabolic activity, while the GI% increased indicating reduced phytotoxicity.     

Bioremediation of glyphosate-contaminated soils

Based on the results of laboratory and field experiments, we performed a comprehensive assessment of the bioremediation efficiency of glyphosate-contaminated soddy-podzol soil. The selected bacterial strains Achromobacter sp. Kg 16 (VKM B-2534D) and Ochrobactrum anthropi GPK 3 (VKM B-2554D) were used for the aerobic degradation of glyphosate. They demonstrated high viability in soil with the tenfold higher content of glyphosate than the recommended dose for the single in situ treatment of weeds. The strains provided a two- to threefold higher rate of glyphosate degradation as compared to indigenous soil microbial community. Within 1–2 weeks after the strain introduction, the glyphosate content of the treated soil decreased and integral toxicity and phytotoxicity diminished to values of non-contaminated soil. The decrease in the glyphosate content restored soil biological activity, as is evident from a more than twofold increase in the dehydrogenase activity of indigenous soil microorganisms and their biomass (1.2-fold and 1.6-fold for saprotrophic bacteria and fungi, respectively). The glyphosate-degrading strains used in this study are not pathogenic for mammals and do not exhibit integral toxicity and phytotoxicity. Therefore, these strains are suitable for the efficient, ecologically safe, and rapid bioremediation of glyphosate-contaminated soils.     

Reductive dechlorination of tetrachloroethene by two compost samples with different maturity

This study sets up microcosms using two types of compost samples, bagasse/manure compost, and yard-trimming compost with different maturity, to evaluate their capacity for reductive dechlorination of tetrachloroethene (PCE). The experimental results show that less matured compost samples could reduce 300 μM of PCE to ethene within 180 days of incubation. Decreasing initial PCE concentration and removing dissolved oxygen from the solution could enhance reducing efficiency. The solution remains near neutral pH throughout the experiment, and ethene emerged when the redox potential dropped to below -150 mV. Different microbial inhibition agents, such as 2-bromoethanesulfonic acid and sodium molybdate 2-hydrate, exhibit different effects on the dechlorination efficiency. The potential advantages of using compost to remove PCE are discussed. Overall, due to their high carbon content, diverse microbial activity, high buffer capacity, and complex physical structure, compost samples could serve as suitable media for dechlorinating PCE.     

Characters of aerated compost tea from immature compost that limit colonization of bean leaflets by Botrytis cinerea

Aims: The aim was to produce and characterize an aerated compost tea (ACT) that suppressed growth of the plant pathogen Botrytis cinerea. Methods and Results: Three different open‐windrow composts were sampled weekly from the early secondary mesophilic stage until maturity. Each 10 kg of compost sample was extracted in 30 l of aerated water for 24, 48 or 72 h. Relative to water, all batches of ACT applied to detached bean leaflets reduced lesion development following single‐point inoculations of B. cinerea. There was a significant linear, inverse relationship between the internal windrow temperature of compost (≤51°C) used to prepare ACT and the extent of lesion development. Bacterial diversity in ACTs from one windrow was highest using compost sampled at 48°C. The compost weight‐to‐water volume ratios of 1 : 3, 1 : 10 or 1 : 30, using compost sampled from a fourth windrow at 50°C, also produced ACTs that reduced the growth of B. cinerea on bean leaflets. The ‘1 : 3’ ACT, and to a lesser degree the same ACT filtered to remove micro‐organisms, inhibited the germination of B. cinerea conidia. Conclusions: ACT produced using the methods reported here suppressed the growth of B. cinerea on bean leaflets, with an abundant and diverse microbial community likely to contribute to pathogen suppression. Significance and Impact of the Study: This is the first report of the use of immature compost to produce a pathogen‐suppressive ACT, suggesting that compost stage is an important production variable.     

Bioremediation of hydrocarbon-contaminated polar soils

Bioremediation is increasingly viewed as an appropriate remediation technology for hydrocarbon-contaminated polar soils. As for all soils, the successful application of bioremediation depends on appropriate biodegradative microbes and environmental conditions in situ. Laboratory studies have confirmed that hydrocarbon-degrading bacteria typically assigned to the genera Rhodococcus, Sphingomonas or Pseudomonas are present in contaminated polar soils. However, as indicated by the persistence of spilled hydrocarbons, environmental conditions in situ are suboptimal for biodegradation in polar soils. Therefore, it is likely that ex situ bioremediation will be the method of choice for ameliorating and controlling the factors limiting microbial activity, i.e. low and fluctuating soil temperatures, low levels of nutrients, and possible alkalinity and low moisture. Care must be taken when adding nutrients to the coarse-textured, low-moisture soils prevalent in continental Antarctica and the high Arctic because excess levels can inhibit hydrocarbon biodegradation by decreasing soil water potentials. Bioremediation experiments conducted on site in the Arctic indicate that land farming and biopiles may be useful approaches for bioremediation of polar soils.     

Bioremediation of oil polluted aquatic systems and soils with novel preparation `Rhoder'

This paper summarises the experience accumulated duringthe field application of biopreparation `Rhoder' (solely or in a combinationwith preliminary mechanical collection of free oil) for remediation of oil polluted aquatic systems and soils in the Moscow region and Western Siberia during 1994–1999.It was demonstrated that `Rhoder' had a very high efficiency (>99%) for bioremediation of the open aquatic surfaces (100 m² bay of the River Chernaya, two 5,000 m² lakes in Vyngayakha) at initial level of oil pollution of 0.4–19.1 g/l. During remediation of the wetland (2,000 m²) in Urai (initial level of oil pollution of 10.5 g/l), a preliminary mechanical collection of oil was applied (75% removal) followed by a triple treatment with `Rhoder'. It resulted in an overall treatment efficiency of 94%. Relatively inferior results of bioremediation of the 10,000 m² wetland in Vyngayakha (65% removal) and the 1,000 m² marshy peat soil in Nizhnevartovsk (19% removal) can be attributed to the very high initial level of oil pollution (24.3 g/l and >750 g/g dry matter, respectively) aggravated by the fact that it was impossible to apply a preliminary mechanical collection of oil on these sites. A possible strategy for remediation of such heavily polluted sitesis discussed.     

Bioremediation 2,4,6,-Trichlorophenol (2,4,6-TCP) by Shigella sp. S2 Isolated from Industrial Dumpsite

A bacterium that utilizes 2,4,6-trichlorophenol (2,4,6-TCP) as a sole source of carbon and energy was isolated from an industrial dumpsite, the bacterium designated as strain S2. Degradation was routinely monitored by observing growth analysis, chloride release assay, and ring cleavage activity and was further confirmed by gas chromatography (GC) analysis. The bacterium was found to degrade up to 90% of 2,4,6-TCP at 1.5 mM concentration. The bacteria were characterized morphologically, biochemically, and by 16S rRNA gene sequencing, which showed 99% sequence similarity with Shigella sp. This is the first report that Shigella sp. was able to degrade 2,4,6-TCP. This strain was found to be novel and a potential 2,4,6-TCP degrader. Further, this strain may be used for bioremediation of 2,4,6-TCP–containing waste in the environment.     

Potassium forms in aerated and anoxic soils of different management and potassium fertilizer history

The potassium forms and dominant clay mineralogy were studied in naturally well-drained (Hapludalfs, Eutropept) and poorly-drained soils (Fragiudalfs, Fragiaquept), both composed of the same parent materials (silty-clay or silt loam or clayey-loam). The well-drained soils (i.e. aerated) were cultivated and received larger amounts of K fertilizer; the poorly-drained types (i.e. anoxic) were grasslands and received low amount of K fertilizer. The different aspects investigated-exchangeable and nonexchangeable K, potassium fixation capacity and clay X-ray diffraction diagrams-indicated that the potassium status and the behavior of K-containing clays significantly differed between naturally well-drained aerated soils and anoxic poorly-drained soils. The aerated soils were high in both exchangeable and nonexchangeable K; the K saturation rate was high whereas fixation capacity was moderate. However, the anoxic soils showed a large K depletion and high fixation capacity. The silty-clayey soils studied were more affected by moisture regimes than the silt loam or clayey-loam.The differing K status between aerated and anoxic soils can be explained by several processes and factors, including soil weathering and management and K fertilizer history.     

白车轴草(Trifolium repens)植株抗病性和生长与植物病史的关系

从白车轴草(Trifolium repens)自然种群中采集无白车轴草单孢锈菌病史的无性系(clones)17个,有白车轴草单孢锈菌病史的无性系14个,分别作为抗病型和感受型植物实验材料;采集白车轴草单孢锈菌(Uromyces trifolii-repentis)菌系(strains)10个,作为病菌实验材料.分别设置并进行了两个温室实验、一个田间盆栽实验和一个原生长地移栽实验,实验处理上分对照、单菌系接种和10个菌系接种等3种.实验结果表明,无论是用单菌系接种还是10个菌系接种,植株发病的概率和程度均与其抗病性有关,抗病型植株(无病史)发病的概率和程度显著低于感受型(有病史)植株.在相同处理的实验中(无论是田间实验还是温室实验),无病史植株和有病史植株的生长无显著差异;不同处理田间实验植株的生长有显著差异,病情愈重,生长愈差.无病史植株的抗病性明显强于有病史植株.但是,原生长地的移栽实验结果表明,在无病原菌存在的情况下,有病史植株的(叶)生长显著好于无病史植株.可以认为,研究生物个体对环境因子反应性差异的实验应当在自然条件下和自然梯度范围内进行.     

低温微生物修复石油烃类污染土壤研究进展

耐冷菌、嗜冷菌等低温微生物广泛存在于极地、高山以及高纬度等土壤环境中,是石油烃类污染物在低温条件下降解与转化的重要微生物资源.利用低温微生物的独特优势,石油污染土壤的低温生物修复技术的研究成为当前热点领域.本文系统综述了低温石油烃降解菌的分类及冷适机制,低温微生物对不同类型石油烃组分的降解特征和降解机理,低温环境中接种降解菌、添加营养物质和表面活性剂等强化技术在石油污染土壤中生物修复的应用.以及微生物分子生物学技术在低温微生物降解石油烃的研究现状,为拓展我国石油污染土壤生物修复技术提供参考.     

Bioremediation of the herbicide glyphosate in polluted soils by plant-associated microbes

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两株绿脓杆菌对石油污染土壤的修复作用

本文旨在研究环境条件下微生物对石油污染土壤的修复情况。从矿井周边土样定向筛选出两株绿脓杆菌,摇瓶降解实验发现,两菌混合培养10 d原油降解率达到95.67%,比单菌培养提高至少32%,即两菌对原油降解具有协同作用。根据降解实验结果制备了混合修复菌剂,并且人工构建石油污染场地,展开中试场地修复试验,模拟不同的操作条件下土壤中原油的降解情况。经60 d修复发现,添加了菌剂的场地,石油烃含量下降趋势明显,每克土壤中石油烃含量从初始的0.8%降至0.1%–0.3%,其中额外添加有机肥作为补充碳氮源的场地,总石油烃降解率最高,达到85.28%。而未添加菌剂的对照组石油烃含量仅减少25.85%。     

Bioremediation of diesel-oil-contaminated alpine soils at low temperatures

Bioremediation of two diesel-oil-contaminated alpine subsoils, differing in soil type and bedrock, was investigated in laboratory experiments at 10 °C after supplementation with an inorganic fertilizer. Initial diesel oil contamination of 4000 mg kg⁻¹ soil dry matter (dm) was reduced to 380–400 mg kg⁻¹ dm after 155 days of incubation. In both soils, about 30 % of the diesel oil contamination (1200 mg kg⁻¹ dm) was eliminated by abiotic processes. The residual decontamination (60 %–65 %) could be attributed to microbial degradation activities. In both soils, the addition of a cold-adapted diesel-oil-degrading inoculum enhanced biodegradation rates only slightly and temporarily. From C/N and N/P ratios (determined by measuring the contents of total hydrocarbons, NH₄ ⁺ N, NO₃ ⁻ N and PO₄ ³⁻ P) of soils␣it could be deduced that there was no nutrient deficiency during the whole incubation period. Soil biological activities (basal respiration and dehydrogenase activity) corresponded to the course of biodegradation activities in the soils. Received: 9 September 1996 / Accepted: 7 December 1996     

Influence of free air space on microbial kinetics in passively aerated compost

The influence of free air space (FAS) on passively aerated composting has been reported, but the quantitative relationship between FAS and the microbial kinetics in passively aerated compost has not been investigated. This relationship was studied by composting dairy manure and straw in an enclosed, passively aerated, cylindrical vessel. Based on this experimental system, conceptual and numerical models were developed in which the compost bed was considered to consist of layered elements, each being physically and chemically homogeneous. The microbial activity in each layer was represented in order to predict oxygen and substrate consumption and the release of water and heat. Convective transport of air, moisture, and heat through the layers was represented. Microbial growth and substrate consumption rates were described using modified first-order kinetics for each of the mesophilic and thermophilic temperature regimes. The values of the microbial kinetic parameters were adjusted for each layer based on an innovative, non-linear, statistical analysis of temperature histories recorded at different layers in the compost bed during three treatments (i.e., FAS values of 0.45, 0.52, and 0.65). Microbial kinetic rate constants were found to follow a sigmoid relationship with FAS, with correlation coefficients (R(2)) of 0.97 for the mesophilic stage and 0.96 for the thermophilic stage. Temperature histories and airflow measurements from a fourth treatment (FAS value of 0.57) were used as an independent check of the model's performance. Simulation results indicate that the model could predict the general trend of temperature development. A plot of the residuals shows that the model is biased, however, possibly because many parameters in the model were not measured directly but instead were estimated from literature. The result from this study demonstrates a new method for describing the relationship between microbial kinetics (k(max)) and substrate FAS, which could be used to improve the design, optimization, and management of passively aerated composting facilities.     

Ecological effects of cow manure compost on soils contaminated by landfill leachate

The experiment was conducted to evaluate the effect of cow manure compost (CMC) application on leaching toxicity of leachate polluted soils by using Tetrahymena pyriformis (TP). Soils treated with various levels of leachate (0, 12.5 ml, 25 ml, 37.5 ml, and 50 ml leachate per 300 g soil) were amended with 0, 25 g and 50 g CMC, respectively. The results showed CMC application resulted in 7–18% lower leaching toxicity while excessive CMC has no significant benefit for decreasing leaching toxicity further. The alleviating effect of CMC on biotoxicity of soil extract was mainly attributed to either pH increase, high content of P and organic matter, or promotion on soil microbial metabolism and especially pH played an important role in alleviating effect. And the observations indicated that death rate (DR) of TP was more sensitive to leachate level respect to other biological parameters above and TP was effective as the test organism for leaching toxicity. Further studies are needed to unambiguously determine in-deep mechanism of toxicity impacts on TP posed by leachate pollutants.     

城市污泥强制通风堆肥过程中的生物学和化学变化特征

采用间竭式强制通风堆肥法进行的肥堆体积约4m3,堆肥时间为53d的污泥堆肥试验表明,堆肥的第2天即达高温阶段(≥55℃)并能保持8d,平均最高温度达68℃,局部温度达74℃.粪大肠杆菌由开始时的1.41×105个·g-1降至试验结束时的2.32×101个·g-1.污泥堆肥过程中挥发性固体,总有机C、水溶性有机C、固体有机 C/N比和水溶性有机 C/有机 N比下降明显,而 N、P及重金属含量有所升高.随着堆肥的进程,在前1周堆肥过程中产生的氨氮大幅下降,硝酸盐含量随之升高.相应地,pH在第1周内升高,随后降低.堆肥40d左右,水芹(Lepidiumsativum L.)种子发芽指数即可达 80%.综合堆肥过程中堆温和化学与生物学变化特点,表明污泥堆肥在40d左右基本上接近腐熟,50d后达到完全腐熟.产品外观呈黑褐色,蓬松,无明显异味.     

两种植物条件下土壤中矿物油和多环芳烃（PAHs）的生物修复研究

选择苜蓿草和水稻为供试植物,以污染物水平、有机以、专性细菌和真菌为调控因子,进行土壤中矿物油和PAHs的生物修复研究,结果表明,投肥对苜蓿草土壤中矿物油降解有促进作用,但对水稻土壤中矿物油降解无明显作用,投肥均使苜蓿草和水稻土壤中多环芒烃总量（11种列于美国EPA黑名单上的多环芳烃）降解率提高,这一降解促进效果在水稻土壤中好于苜蓿草土壤,有机肥量与苜蓿草根际土著真菌、细菌数量明显呈正相关,但仅与水稻根际土著细菌数量呈明显正相关,两种土壤中实测真菌和细菌总数均与试验投加专性真菌和细菌量无关,水稻土和苜蓿草土壤中3环多环芳烃的降解随投肥量增大而降解率提高,其在水稻土蓑中的效果好于苜蓿草土壤,投肥怪4环多环芳烃的降解并未产生有效作用。