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1.
胞外呼吸菌是在厌氧条件下氧化有机物产生电子,进而将电子传递至胞外电子受体并产生能量维持自身生长的一类微生物,在重金属和有机污染物迁移转化过程中发挥着重要作用,且菌群的协同作用效果较单一微生物更为显著。胞外呼吸菌在自然环境中广泛存在,主要集中在变形菌门(Proteobacteria)、放线菌门(Acidobacteria)和厚壁菌门(Firmicutes),且多数为革兰氏阴性菌,其中希瓦氏菌(Shewanella oneidensisi MR-1)和地杆菌(Geobacter sulfurreducens)是研究较为深入的胞外呼吸模式菌。目前已知的5种胞外电子传递机制包括直接电子传递、电子穿梭体、应电运动、纳米导线和细胞间电子传递机制,各种机制非独立存在而是共同作用以促进污染物降解。文章从胞外呼吸菌的种类、胞内与胞外电子传递机制等方面进行综述,并着重论述了胞外呼吸菌在污染物迁移转化中的最新应用进展,为更好地发挥其环境效应提供参考。  相似文献   

2.
土壤微生物铁循环及其环境意义   总被引:9,自引:0,他引:9       下载免费PDF全文
胡敏  李芳柏 《土壤学报》2014,51(4):683-698
铁是土壤中重要的高活性高丰度元素。铁的生物地球化学循环包括铁还原与亚铁氧化两个过程,需要微生物提供基本驱动力,已经成为陆地表层系统研究的国际热点。铁循环控制着土壤有机物矿化、反硝化、甲烷产生、重金属固定等环境过程,是连结土壤养分循环与污染物转化的纽带。从生物地球化学循环的角度,综述了微生物作用下的铁还原、亚铁氧化过程及其主要微生物类群,重点论述了厌氧条件铁还原与亚铁氧化的环境效应及其地球化学机理,以及铁还原与亚铁氧化两个过程的协调及其调控因子。本文将有助于深入理解地球表层的关键环境过程与驱动机制。  相似文献   

3.
微生物直接种间电子传递:机制及应用   总被引:4,自引:0,他引:4  
黄玲艳  刘星  周顺桂 《土壤学报》2018,55(6):1313-1324
微生物种间电子传递(Interspecies electron transfer,IET)是指电子供体微生物与电子受体微生物之间通过直接或间接方式传递电子形成互营生长关系,从而共同完成单一微生物不能完成的代谢过程的现象。IET分为间接种间电子传递(MediatedIET,MIET)和直接种间电子传递(Direct IET,DIET)。其中,前者一般需要氢、甲酸、核黄素等作为电子载体,而后者是指微生物间通过纳米导线、氧化还原蛋白、导电颗粒等进行直接电子交换。DIET是最新发现的IET方式,DIET的发现改变了微生物互营代谢必须依赖氢/甲酸等能量载体的传统认识。本文在论述MIET的同时,重点阐述了DIET的三种介导机制,列举了参与IET的典型微生物种类,系统介绍了IET在厌氧消化产甲烷、甲烷厌氧氧化、微生物脱氯等重要环境过程中的作用机制及应用潜力,并展望了微生物种间电子传递的未来研究方向。本综述有助于加深对微生物IET发生机制的认识,为理解微生物IET在自然界碳氮等元素循环、温室气体排放、污染物降解等关键生物地球化学过程中的作用提供理论基础,为IET的实际工程应用提供可能。  相似文献   

4.
新时代土壤化学前沿进展与展望   总被引:4,自引:1,他引:3  
土壤化学是重要的土壤学基础分支学科。在回顾了土壤化学发展历程的基础上,梳理了土壤化学的四个前沿交叉方向,并展望了土壤化学与其他相关学科的交叉发展趋势,以期寻求新的学科增长点。土壤化学经历了从恒电荷到可变电荷土壤学说演变,我国在土壤电化学、根际土壤化学、土壤化学-物理-微生物界面反应等方向逐步领跑。新时代中国已经发展成为国际土壤化学的研究中心之一,尤其在土壤化学与微生物学、地球化学、矿物学、环境化学等交叉领域取得了突破性发展。同时,发展并运用同步辐射、微流控联用光谱能谱、高分辨显微镜、光谱电化学等实时、原位、高精度研究方法,推动土壤化学研究取得了长足的进步。新时代的土壤化学具有三个重要发展趋势,首先系统揭示地球表层系统中物质循环与能量交换的土壤化学机制,实现"0到1"的土壤化学原创性成果的突破;其次需要综合运用地球表层系统理论,从多界面、多要素、多过程的"三多"交互耦合;再次,需要加强与地球宜居性这一人类重大命题的交叉融合,为生态文明建设、土壤污染防治攻坚战、全球变化等国家重大需求提供理论支持。  相似文献   

5.
土壤胞外呼吸是驱动元素生物地球化学循环的引擎,而微生物纳米导线是实现土壤胞外呼吸的重要途径。微生物纳米导线是一类生长于微生物表面,可长达数十微米的具有导电性的纤维状结构。它直接作用于微生物与土壤矿物、产甲烷与甲烷氧化微生物间的电子传递,从而影响了土壤矿物的迁移转化及温室气体减排。Geobacter sulfurreducens是研究微生物纳米导线的模式微生物。长久以来,基于分子生物学实验证据表明,G. sulfurreducens纳米导线是PilA-N菌毛。而最近基于冷冻电镜技术的纳米导线结构分析发现,G. sulfurreducens实际上表达着各种形式的细胞色素c纳米导线。自此,关于“纳米导线本质”的问题成为学术界争论的焦点。以G. sulfurreducens纳米导线理论发展为主线,综述了不同时期对纳米导线结构与功能的认识,并系统分析了作为“纳米导线本质”争议的证据基础,将推动该争议的早日解决,并助力土壤胞外呼吸理论的成熟及微生物纳米导线的应用研究。  相似文献   

6.
不同施肥条件土壤胡敏酸能态的初步研究   总被引:6,自引:0,他引:6       下载免费PDF全文
地球的腐殖质层是太阳能的巨大贮存库,在陆地的生物能量贮存中,约有50%含于腐殖质中。因此土壤中的有机质转化是最有意义的能量转化过程之一。此外,土壤肥力水平除与腐殖质的数量有关外,腐殖物质的组成、特性也是重要的影响因素。能态是腐殖物质的一种重要特性,腐殖物质能态的研究有助于加深对腐殖物质特性的认识。因此研究土壤腐殖质形成过程的能量转化,以及不同条件下土壤腐殖物质的能态特征具有重要的意义。  相似文献   

7.
甲烷氧化菌以甲烷作为碳源和能源,在全球甲烷平衡和温室效应控制中扮演着重要角色。甲烷生物氧化过程跨越不同氧化还原生态位,近年来的研究表明,在湿地缺氧生态位下变形菌门甲烷氧化菌具有代谢潜力,但其能量代谢机制尚不清楚。本研究基于生物电化学技术、矿物学实验及微生物组学方法,结果表明变形菌门甲烷氧化菌主导的菌群具有直接和间接胞外电子传递潜力;在氧气耗尽时,甲烷氧化菌群可利用水铁矿作为电子受体完成能量代谢过程,缺氧体系中γ-Proteobacteria纲的甲烷氧化菌和非甲烷氧化微生物共同驱动铁矿还原。本研究探讨了变形菌门甲烷氧化菌主导菌群的缺氧能量代谢过程,拓展了反硝化厌氧甲烷氧化菌及厌氧甲烷氧化古菌主导的缺氧甲烷氧化理论,为甲烷生物控制提供了理论支持。  相似文献   

8.
甲烷氧化菌以甲烷作为碳源和能源,在全球甲烷平衡和温室效应控制中扮演着重要角色。甲烷生物氧化过程跨越不同氧化还原生态位,近年来的研究表明,在湿地缺氧生态位下变形菌门甲烷氧化菌具有代谢潜力,但其能量代谢机制尚不清楚。本研究基于生物电化学技术、矿物学实验及微生物组学方法,结果表明变形菌门甲烷氧化菌主导的菌群具有直接和间接胞外电子传递潜力;在氧气耗尽时,甲烷氧化菌群可利用水铁矿作为电子受体完成能量代谢过程,缺氧体系中γ-Proteobacteria纲的甲烷氧化菌和非甲烷氧化微生物共同驱动铁矿还原。本研究探讨了变形菌门甲烷氧化菌主导菌群的缺氧能量代谢过程,拓展了反硝化厌氧甲烷氧化菌及厌氧甲烷氧化古菌主导的缺氧甲烷氧化理论,为甲烷生物控制提供了理论支持。  相似文献   

9.
综述了铁锰氧化菌诱导成矿对重金属环境行为的影响,分别从铁/锰氧化菌与生物成矿、铁/锰氧化菌诱导铁锰氧化物沉淀耦合重金属稳定化以及铁锰氧化物对土壤中重金属的作用方面进行阐述;并从铁/锰氧化菌生物成矿方式、铁/锰氧化菌诱导生物成矿过程对土壤重金属的稳定化机制等方面进一步总结了铁/锰氧化菌在不同重金属生物成矿修复中的应用,以及微生物诱导成矿过程的调控因素,分析胞外聚合物、温度与酸碱度、共存离子和其他因素对成矿过程的影响,以期为微生物诱导成矿修复重金属污染提供理论参考。未来工作可进一步关注生成矿物稳定重金属的长效性,不同微生物菌群组合对成矿效果的调控,以及铁/锰氧化菌在重金属复合污染场地土壤修复中的应用等方面。  相似文献   

10.
分形理论在土壤肥力研究中的应用与前景   总被引:3,自引:2,他引:1  
蒋先军  李航  谢德体  魏朝富  熊海灵 《土壤》2007,39(5):677-683
分形理论的提出对于定量描述复杂的、高度不规则的系统特征与机理提供了方法.本文从土壤腐殖质、土壤微生物、土壤团聚体等方面回顾了分形理论在土壤肥力研究中的主要结果:土壤腐殖质胶体在不同条件下形成不同分形特征的聚合物;同一种微生物可能形成具有不同分形特征的结构;土壤中的有机无机胶体在不同条件下凝聚成不同的团聚体,从而形成不同的土壤结构并对其肥力功能产生影响.我们认为分形理论在探索土壤的形成过程和肥力功能上将具有重要的应用前景:如团粒结构体的形成可能是由土壤胶体分形凝聚而成;土壤中的活性有机质有逐渐老化的现象,可能和腐殖质胶体由结构疏松的分形结构向普通团聚体过渡的过程有关;土壤微生物在不同微环境下具有不同的分形特征,可以推测在各种土壤过程(包括物理、化学以及生物化学过程)中它们的功能也可能是不一样的.此外,土壤结构的开放程度决定孔隙、水分以及空气的分布,从而决定了微生物的生存空间.所以土壤结构体对微生物空间分布的影响也是将来该领域值得研究的内容之一.  相似文献   

11.
铁矿物作为土壤的重要组成成分,一般可通过吸附、络合和共沉淀等方式影响重金属的生物有效性和毒性。此外,土壤中有机物的存在会影响铁矿物的转化,导致转化产物的结构和表面特性发生改变,进一步影响重金属的环境行为。本文从铁矿物、有机质和重金属等要素入手,综述了反应pH、温度、亚铁和微生物等因素影响下土壤铁矿物非生物和生物转化过程、土壤有机物对铁矿物转化过程的影响机制、土壤铁矿物界面重金属反应机制以及土壤铁矿物-有机质相互作用下的重金属反应机制。最后,对今后在复杂的自然环境中深入揭示铁矿物转化机制、原位观测重金属在矿物-水界面的微观反应机制以及预测和评估重金属的归趋等有关方向进行了展望。  相似文献   

12.
Purpose

Humins, as solid-phase redox mediators, are important for enhancing anaerobic biotransformation processes. Although humins are broadly distributed in estuarine and marine sediments, to date, their electron transfer capacity (ETC) from marine sediments has been poorly characterized. This study determined the potential of humins as redox mediators for microbial redox metabolic reactions in sediments along a transect from the Yangtze Estuary to the adjacent East China Sea and analyzed their electron-mediating characteristics.

Materials and methods

Comparative analyses of humins in sediments along this transect were conducted to investigate their ETC as redox mediators for microbial redox metabolic reactions, namely dissimilatory iron reduction (DIR) and dissimilatory nitrate reduction to ammonium (DNRA), using Shewanella oneidensis MR-1. Elemental composition, electrochemical, and Fourier transform infrared analyses were performed to better understand the functional redox groups in humins.

Results and discussion

All the humins functioned as solid-phase redox mediators and enhanced DIR and DNRA by Shewanella oneidensis, although with varying efficacy. The humins extracted from sampling site P1 (P1-HM), located close to the Yangtze Estuary, most effectively enhanced iron and nitrate reduction without nitrite accumulation. Electrochemical analysis confirmed the highest redox activity and ETC in P1-HM and a weakening trend of ETC with increasing distance from the estuary. Fourier transform infrared analysis suggested that quinone moieties might serve as key redox functional groups in humins.

Conclusions

Considering their high yield and ETC, P1-HM could be important redox mediators that influence microbial redox metabolic reactions in sedimentary ecosystems of the Yangtze Estuary. Thus, this study provides insights into the distribution of humins, their ECT, and their potential role as redox mediators for microbial redox reactions, which could improve understanding of elemental biogeochemical cycling processes involving microorganisms in the Yangtze Estuary and East China Sea sedimentary ecosystems and provide important reference information for researches on other estuary areas.

  相似文献   

13.

Purpose

Dissolved organic matter (DOM) has been shown to be an efficient electron transfer facilitator in biogeochemical reactions due to its ability to mediate redox reactions. It has been known that various fractions of DOM differed in their chemical and biogeochemical behaviors in environment. However, there has been relatively little work directed at predicting the dependence of redox properties of DOM on its fractions.

Materials and methods

DOM was extracted from sewage sludge compost. Freeze-dried DOM was grouped into three fractions of different molecular sizes (<3,500, 3,500–14,000, and >14,000 Da) using dialysis bags (Spectra/Por 3 and 4, Spectrum Industries, California, US). Cycle voltammetry was used to investigate the redox behavior of the fractions. Chronoamperometry was employed to study their electron accepting capacities and electron donating capacities by applying fixed positive or negative potential to the working electrode in a conventional three-electrode cell. Fourier-transform infrared and three-dimensional excitation/emission matrix fluorescence spectroscopies were used to determine the functional groups in the fractions. Shewanella putrefaciens 200 (SP200) and Klebsiella pneumoniae L17 (L17) were used for all microbial iron(III) reduction experiments.

Results and discussion

Electrochemical methods show that the electron transfer capacity (ETC) of DOM depends on its molecular weight, and ETC is in the order of high-molecular weight DOM (H-DOM) > moderate-molecular weight DOM > low-molecular weight DOM. The same trend is discovered in the DOM-stimulated iron(III) oxide bioreduction where DOM fractions act as electron shuttles transferring electrons from the Fe(III)-reducing bacteria to the iron oxide. Both spectroscopic and cyclic voltammogram assays show the highest abundance of redox moieties associated to H-DOM, which is possibly responsible for its strongest electron-shuttling ability.

Conclusions

DOM has a wide molecular weight (MW) distribution due to the complexity of its chemical composition and structure. In addition to structural variations, DOM fractions with different MW have different redox properties and electron-shuttling capacities in microbial Fe(III) reduction. The results are of great significance for further studies on DOM geochemical behavior in environment.  相似文献   

14.

Purpose

The thermodynamic energy of redox reactions affects the distribution of microbial redox reactions and cyclic transformation of elements in various anaerobic ecosystems. The principle of thermodynamics is of dramatic significance in understanding the energetics of metabolic processes, the biogeochemical behavior of microorganisms, and mass and energy cycles. The purpose of this paper is to relate the distribution of the coupling reactions between C, N, Fe, and S, the most important elements involved in microbially mediated redox reactions, with their thermodynamic feasibility to provide theoretical foundation of their occurrence.

Results and discussion

Anaerobic microorganisms catalyze diverse redox reactions in anoxic environments, driving elemental biogeochemical cycles on the earth. They capture energy from catalyzing these redox reactions in order to support life. The thermodynamic feasibility of these microbe-driven redox reactions is controlled by their energy yields which depend on environmental conditions. Anaerobic microorganisms can oxidize organic carbon with diverse inorganic compounds including nitrate/nitrite, ferric iron, and sulfate as electron acceptors in various anoxic environments which is referred to anaerobic respiration of organic matter; reversely, inorganic carbon can be reduced to synthesize cell material with ferrous iron and sulfide as an alternative electron donor by phototrophs under different sets of circumstances. Nitrate/nitrate can be microbically reduced by inorganic compounds such as ferrous iron and sulfide under some specific situations; the coupling of anaerobic anammox oxidation and reduction of nitrite (anammox), ferric iron (feammox), and sulfate (suramox) driven by anaerobes occurs in other particular systems.

Conclusions and perspectives

Although there are increasing researches investigating the anaerobe-driven coupling of pairs of elements such as C-N, C-Fe, C-S, N-Fe, N-S, and Fe-S, much more intricate situations associating the coupling of multiple elements are still not comprehensively understood. A great many reactions which are thermodynamically feasible have not yet been identified in natural environments or laboratories. Further work focusing on the metabolic pathways from a genetic and enzymatic perspective and the factors controlling the feasibility of the reactions by using updated technical tools and methods is required.
  相似文献   

15.
The chemistry of pedogenic thresholds   总被引:5,自引:0,他引:5  
Oliver A. Chadwick  Jon Chorover   《Geoderma》2001,100(3-4):321-353
Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid–base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation–reduction processes through a stepwise consumption of electron acceptors (thereby producing thresholds) but disequilibrium among redox couples and regeneration of redox buffer capacity may attenuate this response. Synthesis of secondary minerals, ranging from carbonates and smectites to kaolinite and oxides, forms a basis for many of the reported cases of pedogenic inertia and thresholds. Mineralogical change tends to occur in a serial, irreversible fashion that, under favorable environmental conditions, can lead to large accumulations of specific minerals whose crystallinity evolves over time. These accumulations and associated “ripening” processes can channel soil processes along existing pathways or they can force thresholds by causing changes in water flux and kinetic pathways.  相似文献   

16.
It has been established that soil moisture has a significant impact on the activity of chitinolytic microbial processes, rather than pectinolytic processes. The degradation of polysaccharides with an increase in soil moisture in microbial complex markedly increases the role of prokaryotic microorganisms, especially actinomycetes. For the first time, using the FISH method, the amount of detected phylogenetic composition of a metabolically active hydrolytic complex of humus horizons of grey forest and gley and weakly podzolic soil and humus has been estimated depending on the humidity. At optimum moisture, phylogenetic groups Actinobacteria and Firmicutes dominated in the chitinolytic process. An increase in the proportion of proteobacteria is observed with an increase in humidity. The role of gamma- and alphaproteobacteria and actino-bacteria is heightened with the drying of soil in the hydrolytic complex. A quantitative estimate of the rate of degradation of polysaccharides (pectin and chitin) in different types of soils at different levels of moisture is given. The dependence of the phylogenetic composition of an active microbial hydrolytic complex of humus horizons of grey forest and gley, weakly podzolic soils and humus on humidity is revealed.  相似文献   

17.
微生物残体在土壤中的积累转化过程与稳定机理研究进展   总被引:3,自引:0,他引:3  
张彬  陈奇  丁雪丽  何红波  张旭东 《土壤学报》2022,59(6):1479-1491
近年来,关于微生物残体在土壤有机质积累和转化过程中的作用越来越受到研究者的关注。土壤有机质中微生物残体的数量和组成比例变化与土壤有机质的形成、容量大小及周转特征密切相关。对目前土壤微生物残体研究方面的相关进展进行了梳理和总结,在明确土壤微生物残体的来源及其重要性的基础上,介绍了土壤微生物残体定量和转化的表征方法,阐述了微生物残体在土壤有机质积累转化过程中的作用及其主要影响因素,探讨了微生物残体在土壤中的稳定机制,提出了微生物通过同化代谢作用驱动细胞残体积累进而促进土壤有机质积累和稳定过程中亟待探讨的科学问题。期望为进一步探究陆地生态系统土壤有机质周转与微生物过程的相互作用机理提供一定的思考。  相似文献   

18.
Our understanding of the interactions between minerals, organic matter, and microorganisms at so-called biogeochemical interfaces in soil is still hampered by the inherent complexity of these systems. Artificial soil maturation experiments can help to bridge a gap in complexity between simple abiotic sorption experiments and larger-scale field experiments. By controlling other soil-forming factors, the effect of a particular variable can be identified in a simplified system. Here, we review the findings of a series of artificial soil incubation experiments with the aim of revealing general trends and conclusions. The artificial soils were designed to determine the effect of mineral composition and charcoal presence on the development of abiotic and biotic soil properties during maturation. In particular, the development of soil aggregates, organic matter (OM) composition and turnover, sorption properties, and the establishment of microbial community composition and function were considered. The main objectives of the research were to determine (1) how surface properties and sorption of chemicals modify biogeochemical interfaces; (2) how much time is required to form aggregates from mixtures of pure minerals, OM, and a microbial inoculum; and (3) how the presence of different mineral and charcoal surfaces affects aggregation, OM turnover, and the development of microbial community composition.  相似文献   

19.
The stabilization of SOM by Al–humus complexes and non-crystalline minerals is a key issue to explain the soil-C variability and the biogeochemical processes that determine the fate of soil C following land-use/cover change (LUCC) in volcanic landscapes. In an altitudinal gradient of volcanic soils (2550–3500 masl), we quantified the total soil C (CT) concentrations and stocks in soil pits sampled by genetic horizons. We performed analyses at landscape and local scales in order to identify and integrate the underlying environmental controls on CT and the effects of LUCC. We selected four sites, two on the upper piedmont, one on the lower mountain slope and one on the middle mountain slope at Cofre de Perote volcano (eastern central Mexico) where temperate forests are the natural vegetation. At each site we selected three to five units of use/cover as a chronosequence of the LUCC pathways. In each soil horizon chemical characteristics (i.e. N, C/N ratio, pH, exchangeable bases) were determined and mineralogical properties were estimated from selective Al, Fe and Si oxalate and pyrophosphate extractions (i.e. the Alp/Alo ratio, the active Al related to non-crystalline minerals as Alo ? Alp, the allophane concentration, and the non-crystalline Al and Fe minerals as Alo + 1/2Feo). At landscape scale, the Al–humus complexes were strongly related to the CT concentration in topsoil (A horizons) but this relationship decreased with depth. In turn, the non-crystalline minerals and the C/N ratio explained the variability of the CT concentrations in C horizons. At local scale, CT concentrations and stocks were depleted after conversion of forest to agriculture in Vitric Andosols at the upper piedmont but this was not observed in Silandic Andosols. However, in Vitric Andosols the reduction of the CT stocks is partially recovered throughout the regeneration/reforestation processes. The results suggest that the lower vulnerability of Silandic Andosols than Vitric Andosols to changes in the CT after LUCC is due to the higher levels of SOM stabilized by Al–humus complexes and non-crystalline minerals in the Silandic soils. Furthermore, the importance of the allophane to explain the CT stocks in the Silandic Andosols of the middle slopes suggests that the CT stabilized by this mineral fraction in the subsoil adds an important fraction of the CT to the estimates of the stocks.  相似文献   

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