典型矿冶区周边土壤微生物功能特征及影响因素

土壤微生物对重金属污染胁迫敏感,但在实际野外环境中,土壤微生物群落生态效应通常是污染胁迫和环境因素综合作用的结果。为探究重金属污染土壤中微生物群落生态效应发生变化的主控因素,本研究以湖南省某典型矿冶区周边不同土地利用类型土壤为研究对象,以土壤碳氮循环过程主要的微生物功能指标土壤微生物生物量碳(MBC)、基础呼吸(BR)、诱导呼吸(SIR)和硝化潜势(PNR)为生态效应终点,进行采样调查分析。结果表明: 土地利用类型对MBC、BR和SIR影响均不显著;研究区土壤微生物功能的主要影响因子包括CaCl₂提取态Pb(CaCl₂-Pb)含量与土壤有机质(SOM)含量。多元回归分析结果表明,在CaCl₂-Pb含量为0.004～13.14 mg·kg^-1及SOM含量为0.24%～4.34%的条件下,土壤CaCl₂-Pb和SOM含量可以共同解释土壤中BR、SIR和PNR总变异的39.8%～58.3%;中等含量下(SOM在1.70%～2.36%,CaCl₂-Pb在0.004～12.98 mg·kg^-1),土壤CaCl₂-Pb和SOM含量与BR、SIR和PNR的变化能够建立显著的暴露-效应关系,可以作为测定终点定量评价重金属污染对微生物群落功能的生态效应。     

重金属胁迫下的微生物代谢组学研究进展

微生物的代谢活动易受到环境变化的影响,当环境中存在重金属污染时微生物会通过调节代谢降低自身所受的重金属的毒害。本文通过微生物代谢组学研究探讨重金属胁迫下微生物代谢活动的响应情况,介绍了微生物代谢组学的相关技术和方法,对其应用进行说明;基于重金属对微生物细胞的毒害作用,对重金属胁迫下微生物代谢组学的相关内容进行综述,发现在重金属胁迫下,微生物可以通过增加代谢活动进而产生更多的代谢物质来响应重金属的胁迫,其中微生物产生的胞外聚合物、草酸和柠檬酸等代谢物在微生物响应重金属胁迫中具有重要作用。微生物通过产生相应代谢物不仅使自身可以在重金属胁迫下生存,这些代谢物还可以使环境中重金属有所减少,这对于利用微生物资源修复重金属污染具有重要意义。     

水分条件变化对土壤微生物的影响及其响应机制研究进展

土壤微生物在维持陆地生态系统服务中扮演着重要的角色.土壤水分条件是影响微生物活性与生态系统功能的重要因素之一,全球气候变化所引起的极端干旱与降雨必将加速土壤水分的剧烈变化.由于不同土壤微生物对干旱胁迫的耐受性不同及其对水分变化的响应差异,使得土壤水分条件变化直接改变了土壤微生物活性与群落结构,进而对微生物介导的关键过程与土壤生态系统功能造成深刻的影响.因此,全面深入地理解水分条件变化下土壤微生物群落的结构变化特征与响应机制具有重要意义.本文在总结土壤水分条件变化对土壤微生物活性(土壤呼吸与酶活性)和微生物群落结构的影响的基础上,进一步阐述了土壤微生物对干旱胁迫与水分条件变化的响应机制和生态学策略,包括: 1)积累胞内溶质、产生胞外聚合物、进入休眠状态等应对干旱胁迫的细胞生理策略;2)微生物之间、微生物与植物之间相关抗逆性基因的转移及土壤微生物群落的功能冗余等应对水分变化的微生物机制.研究水分条件变化下土壤微生物群落结构及生态系统功能之间的内在联系,不仅有助于进一步剖析微生物介导的土壤生态过程,而且能够为今后陆地生态系统对气候变化的响应研究和模型预测提供理论依据.     

重金属对土壤微生物的生态效应

通过分析重金属对土壤微生物生化过程与数量、种群及群落的影响、影响重金属对土壤微生物毒性的因素、重金属对土壤微生物毒性的评价指标、微生物对重金属的耐性与适应性以及重金属毒性的差异 ,综合评述了重金属对土壤微生物的生态效应 .     

重金属土壤微生物的生态效应

通过分析重金属对土壤微生物生化过程与数量、种群及群落的影响、影响重金属对土壤微生物毒性的因素、重对土壤微生物毒性的评价指标、微生物对重金属的耐性与适应性以及重金属毒性的差异,综合评述了重金属对土壤微生物生态效应。     

重金属污染对土壤微生物生态的影响

土壤重金属污染面积大,波及范围广,是一个全球性的环境问题。重金属的大量积累会降低土壤中微生物的生物量和活性,甚至会影响微生物群落的结构和多样性。土壤微生物由于其高灵敏度和及时对环境因素作出变化而越来越多地被用作监控土壤质量的生物指标。现主要针对土壤中重金属污染在土壤微生物活性、生物量、微生物群落结构等方面的影响进行综述。结合现有研究因素综合考虑,对微生物生态学研究指标在重金属土壤修复领域进行展望,为重金属污染土壤研究提供更为全面的质量评价和有效指标。     

土壤微生物群落对全球气候变化响应的研究进展

全球气候变化对陆地生态系统过程和功能产生重要影响,土壤微生物群落在陆地生态系统几乎所有的生物地球化学循环过程起到关键作用。本文针对气候变化对土壤微生物的影响研究结果,主要从土壤微生物活性(土壤呼吸与酶活性)和微生物群落结构对大气CO₂升高、增温、降水变化、氮沉降等全球变化单因子和多因子的直接或间接响应进行综述,并进一步阐述参与土壤碳氮循环过程的功能微生物对气候变化的响应机制与适应规律。全球变化因子改变了土壤微生物的群落组成,呈现降低、增加和无影响3种效应,且不同功能微生物也呈现不同的敏感性。多个全球变化因子对土壤微生物群落结构的交互效应可能存在加性、协同、拮抗作用,产生加和的、相互促进或抵消的整体效果。然而,目前对多种全球变化因子如三因子或四因子的组合作用,以及多因子的高阶交互作用研究较少;已有的研究地理分布不均匀,且时间和空间大尺度的研究不足;缺乏综合生态系统模型对全球变化的影响进行模拟和预测。最后指出今后的研究发展方向：进行多种全球变化因子、长时间、多生态系统点位、大空间尺度的土壤微生物群落动态研究;探究多种全球变化因子的高阶交互作用;建立综合响应的生态系统模...     

谷子及其根际土壤微生物群落对铬胁迫的响应机制

重金属铬(Cr)污染对农田中农作物产生毒害作用并破坏土壤微生物群落稳态,但不同农作物及其根际土壤微生物群落对Cr胁迫的响应机制均有所差异。该研究在时间序列上分析Cr胁迫对谷子(正名:粱, Setaria italica)长势、谷子差异表达基因(DEGs)的功能途径及土壤微生物群落结构和功能等方面的影响,阐明谷子及土壤微生物群落的响应机制,为Cr胁迫下的谷子生长及污染土壤的生态修复治理提供理论依据。基于室内盆栽实验,以谷子幼苗和种植谷子的土壤为实验材料,在Cr胁迫前(CK)及胁迫后6 h和6 d (Cr＿6h、Cr＿6d)的时间序列上分别进行样本采集,同时测量幼苗生理性状指标及土壤理化指标。通过转录组分析,研究Cr胁迫时间序列上谷子幼苗基因表达及所富集的功能途径的变化趋势;通过高通量测序分析,研究Cr胁迫时间序列上土壤微生物群落结构、物种多样性、群落功能的动态变化过程及与土壤理化性质的相关性。结果发现:1)转录组分析结果表明Cr胁迫诱导基因表达上调(上调DEGs 54%); Gene Ontology (GO)富集分析表明DEGs在CK和Cr＿6h、Cr＿6h和Cr＿6d样本对中与光合作...     

土壤重金属污染的微生物生态效应研究进展

对近年来土壤重金属污染微生物生态效应的研究进展进行了归纳总结,主要从微生物群落特性和微生物生理、生化参数等几个方面进行了阐述。重金属污染土壤后,尤其是高浓度的重金属污染对微生物生物量和群落结构都有破坏作用,但由于微生物群落结构的复杂性和研究方法的片面性,一直是研究的热点和难点,开发更加简便、直接的方法将是对这方面研究的突破。同时,微生物的生理、生化参数是从另一侧面反映重金属污染对微生物的影响,它是对微生物群落特性研究的有利补充,所以不同方法的合理选择和搭配是实验取得预期结果的关键因素之一。     

鸡粪有机肥对设施菜地土壤重金属和微生物群落结构的影响

通过田间试验,研究在设施菜地上施用不同剂量的鸡粪有机肥对土壤-植物系统中重金属的累积、重金属有效性和土壤微生物群落结构的影响,进一步探讨土壤微生物群落结构与土壤重金属之间的相关关系。结果表明,与对照相比,施用有机肥可提高小白菜地上部生物量,其中施肥量为60 t/hm²时值最大,增幅为59.92%;小白菜地上部Cd、Cr、Cu、Zn和As含量均大幅增加,但Pb含量无明显变化。土壤重金属Cd、Cr、Cu、Zn和As的全量均随鸡粪有机肥施加量的增加而增大,最高增幅分别为21.30%、21.58%、17.40%、19.40%和17.43%,出现明显的累积现象;施用有机肥均增加了土壤Cd、Cr、Cu、Zn和As的有效态含量,而Pb的全量和有效态含量无显著变化;除重金属Pb外,不同重金属元素全量与有效态含量均显著正相关,其中元素Zn的全量与有效态含量相关性最强。磷脂脂肪酸（PLFA）分析结果表明,土壤中含量较高的PLFA为16：0、18：1ω7c、10Me16：0和18：1ω9c,土壤微生物总PLFA和各类群PLFA含量均呈现M0.5 > M1 > CK > M2 > M4;相关性分析结果表明,土壤Cu、As全量和Cd、Cr、Cu、As有效态含量与微生物总PLFA和各类群PLFA含量均呈现显著负相关关系,其中有效态Cr和Cu含量对微生物群落结构的影响最为显著。     

Assessing Risks of Heavy Metal Toxicity in Agricultural Soils: Do Microbes Matter?

Deleterious effects of heavy metals on soil microorganisms are reviewed in relation to the complexities involved in their study. There is strong evidence that soil microbes are more sensitive to heavy metals than animals or crop plants. Decisions concerning limits considered to be ‘safe’ in terms of protection of soil microorganisms or soil microbial processes from metal toxicity depend on the organisms considered and value judgements as to their importance. At present there is a large discrepancy in actual concentrations of heavy metals that are allowed to accumulate in agricultural soils between different countries. The approach of attempting to achieve zero accumulation of heavy metals in soils is undoubtedly the most conservative, but will severely restrict the recycling of sewage sludges to agricultural land.     

土壤重金属生物毒性研究进展

世界范围内土壤重金属污染不断加重,由污染所带来的问题以及如何治理污染已经受到人们越来越多的关注.土壤重金属将对土壤生物产生影响,而土壤生物在重金属的胁迫下也会产生不同的响应.综述了国内外近年来土壤重金属生物毒性的研究进展,介绍了土壤重金属污染对陆地生态系统中植物、动物和微生物生长的影响;土壤重金属生物毒性的影响因素;土壤重金属生物毒性的研究方法;土壤重金属生物毒性的预测模型,最后提出了问题和展望.     

Long-term effects of metals in sewage sludge on soils,microorganisms and plants

Summary This paper reviews the evidence for impacts of metals on the growth of selected plants and on the effects of metals on soil microbial activity and soil fertility in the long-term. Less is known about adverse long-term effects of metals on soil microorganisms than on crop yields and metal uptake. This is not surprising, since the effects of metals added to soils in sewage sludge are difficult to assess, and few long-term experiments exist. Controlled field experiments with sewage sludges exist in the UK, Sweden, Germany and the USA and the data presented here are from these long-term field experiments only. Microbial activity and populations of cyanobacteria,Rhizobium leguminosarum bv.trifolii, mycorrhizae and the total microbial biomass have been adversely affected by metal concentrations which, in some cases, are below the European Community's maximum allowable concentration limits for metals in sludge-treated soils. For example, N₂-fixation by free living heterotrophic bacteria was found to be inhibited at soil metal concentrations of (mg kg^–1): 127 Zn, 37 Cu, 21 Ni, 3.4 Cd, 52 Cr and 71 Pb. N₂-fixation by free-living cyanobacteria was reduced by 50% at metal concentrations of (mg kg^–1): 114 Zn, 33 Cu, 17 Ni, 2.9 Cd, 80 Cr and 40 Pb.Rhizobium leguminosarum bv.trifolii numbers decreased by several orders of magnitude at soil metal concentrations of (mg kg^–1): 130–200 Zn, 27–48 Cu, 11–15 Ni, and 0.8–1.0 Cd. Soil texture and pH were found to influence the concentrations at which toxicity occurred to both microorganisms and plants. Higher pH, and increased contents of clay and organic carbon reduced metal toxicity considerably. The evidence suggests that adverse effects on soil microbial parameters were generally found at surpringly modest concentrations of metals in soils. It is concluded that prevention of adverse effects on soil microbial processes and ultimately soil fertility, should be a factor which influences soil protection legislation.     

Using the stress response to monitor process control: pathways to more effective bioremediation

Environmental contamination with a variety of pollutants has prompted the development of effective bioremediation strategies. But how can these processes be best monitored and controlled? One avenue under investigation is the development of stress response systems as tools for effective and general process control. Although the microbial stress response has been the subject of intensive laboratory investigation, the environmental reflection of the laboratory response to specific stresses has been little explored. However, it is only within an environmental context, in which microorganisms are constantly exposed to multiple changing environmental stresses, that there will be full understanding of microbial adaptive resiliency. Knowledge of the stress response in the environment will facilitate the control of bioremediation and other processes mediated by complex microbial communities.     

Effect of heavy metal pollution on mycorrhizal colonization and function: physiological, ecological and applied aspects

 High concentrations of heavy metals in soil have an adverse effect on micro-organisms and microbial processes. Among soil microorganisms, mycorrhizal fungi are the only ones providing a direct link between soil and roots, and can therefore be of great importance in heavy metal availability and toxicity to plants. This review discusses various aspects of the interactions between heavy metals and mycorrhizal fungi, including the effects of heavy metals on the occurrence of mycorrhizal fungi, heavy metal tolerance in these micro-organisms, and their effect on metal uptake and transfer to plants. Mechanisms involved in metal tolerance, uptake and accumulation by mycorrhizal hyphae and by endo- or ectomycorrhizae are covered. The possible use of mycorrhizal fungi as bioremediation agents in polluted soils or as bioindicators of pollution is also discussed. Accepted: 23 June 1997     

Microorganisms and heavy metal toxicity

The environmental and microbiological factors that can influence heavy metal toxicity are discussed with a view to understanding the mechanisms of microbial metal tolerance. It is apparent that metal toxicity can be heavily influenced by environmental conditions. Binding of metals to organic materials, precipitation, complexation, and ionic interactions are all important phenomena that must be considered carefully in laboratory and field studies. It is also obvious that microbes possess a range of tolerance mechanisms, most featuring some kind of detoxification. Many of these detoxification mechanisms occur widely in the microbial world and are not only specific to microbes growing in metal-contaminated environments.     

Understanding molecular mechanisms for improving phytoremediation of heavy metal-contaminated soils

Heavy metal pollution of soil is a significant environmental problem with a negative potential impact on human health and agriculture. Rhizosphere, as an important interface of soil and plants, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria or mycorrhizas have received more and more attention. In addition, some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals, and they manage to survive under metal stresses. High tolerance to heavy metal toxicity could rely either on reduced uptake or increased plant internal sequestration, which is manifested by an interaction between a genotype and its environment.A coordinated network of molecular processes provides plants with multiple metal-detoxifying mechanisms and repair capabilities. The growing application of molecular genetic technologies has led to an increased understanding of mechanisms of heavy metal tolerance/accumulation in plants and, subsequently, many transgenic plants with increased heavy metal resistance, as well as increased uptake of heavy metals, have been developed for the purpose of phytoremediation. This article reviews advantages, possible mechanisms, current status and future direction of phytoremediation for heavy-metal–contaminated soils.     

Metal toxicity and ectomycorrhizas

Metal toxicity (Al and heavy metals) is a major constraint affecting root growth in a number of natural or managed ecosystems. Fine roots of the majority of plant species are associated with mycorrhizal fungi, which may modify the sensitivity of roots to metal stress. In this review, we summarise the available evidence demonstrating beneficial effects of ectomycorrhizas in alleviation of metal toxicity in forest tree seedlings. We identify experimental shortcomings of past research (e.g. the use of shoot metal concentrations as a measure of metal uptake, use of microanalytical techniques biased by element redistribution) that may confound major conclusions drawn from these experiments. Although there is no doubt that in many cases ectomycorrhizal fungi indeed ameliorate metal stress in their host plants, the mechanism(s) involved remain(s) unclear. The role of metal sorption on fungal tissues thought to reduce metal exposure of the host plant is critically reviewed. As direct evidence (both under artificial and soil conditions) supporting a unique role of fungal immobilisation of metals is lacking so far, there is an urgent need to also test alternative tolerance mechanisms such as the release of metal chelating substances, or nutritional and hormonal effects mediated by mycorrhizal fungi.     

Environmental impact and bioremediation of seleniferous soils and sediments

Selenium concentrations in the soil environment are directly linked to its transfer in the food chain, eventually causing either deficiency or toxicity associated with several physiological dysfunctions in animals and humans. Selenium bioavailability depends on its speciation in the soil environment, which is mainly influenced by the prevailing pH, redox potential, and organic matter content of the soil. The selenium cycle in the environment is primarily mediated through chemical and biological selenium transformations. Interactions of selenium with microorganisms and plants in the soil environment have been studied in order to understand the underlying interplay of selenium conversions and to develop environmental technologies for efficient bioremediation of seleniferous soils. In situ approaches such as phytoremediation, soil amendment with organic matter and biovolatilization are promising for remediation of seleniferous soils. Ex situ remediation of contaminated soils by soil washing with benign leaching agents is widely considered for removing heavy metal pollutants. However, it has not been applied until now for remediation of seleniferous soils. Washing of seleniferous soils with benign leaching agents and further treatment of Se-bearing leachates in bioreactors through microbial reduction will be advantageous as it is aimed at removal as well as recovery of selenium for potential re-use for agricultural and industrial applications. This review summarizes the impact of selenium deficiency and toxicity on ecosystems in selenium deficient and seleniferous regions across the globe, and recent research in the field of bioremediation of seleniferous soils.     

微生物胞外多糖的合成及其在重金属修复中的作用机制与应用

重金属的生物不可降解性使其在环境中长期存在,导致严重的环境污染,对人类健康和生态系统构成威胁。与传统的物化修复技术相比,微生物修复具有成本低廉、环境友好和高效等特点。在面对重金属胁迫或营养不均衡时,微生物会被激发以分泌合成胞外多糖(exopolysaccharides, EPS)。由此可见,EPS的产生是微生物对抗重金属胁迫的重要策略之一。EPS不仅能保护微生物在低温、高温、高盐等极端环境或受毒性化合物胁迫的条件下存活,并且在细胞内外进行信息和物质的交流与传递,既作为保护屏障限制重金属离子进入细胞,又作为介质进行交流。EPS结构中含有多个带负电荷的官能团,能够与重金属离子发生络合、离子交换、氧化还原等反应,从而降低重金属的生物有效性并减轻其毒性。微生物EPS在重金属胁迫环境中的修复具有重要意义。然而,目前缺乏关于微生物EPS合成过程、与重金属互作机制及其在重金属胁迫环境中应用现状的系统综述。本文概述了微生物EPS及其分类,详细阐述了细菌EPS胞内及胞外的生物合成机制,并探讨了微生物EPS与重金属互作机制,以及微生物EPS修复水、土环境中重金属污染方面的研究进展。最后,展望了EPS合成及其在重金属修复中的作用机制研究,可为微生物EPS进一步应用于环境重金属污染修复提供支持。