自然生境中亚硝酸盐型厌氧甲烷氧化细菌研究进展

随着功能微生物介导的亚硝酸盐型厌氧甲烷氧化(nitrite-dependent anaerobic methane oxidation,N-DAMO)过程被发现,人们对自然界的碳氮循环有了全新的认识,该过程成为自然生态系统中温室气体甲烷的汇,同时还是氮污染的消减途径。本文系统介绍了N-DAMO过程反应机理以及参与该过程的亚硝酸盐型厌氧甲烷氧化细菌(Candidatus Methylomirabilis oxyfera)的生理生化特征,并对研究该功能菌的分子微生物方法进行了汇总。通过对不同自然生境中该细菌的研究报道进行总结分析,揭示各生境中年均降水量、年均温度、所处不同自然区等大尺度宏观环境因子及碳源、氮源、pH和氧气含量等生存因子对其群落结构的潜在影响,最后在展望中提出此功能菌在未来可深入研究的方向,期望能厘清厌氧甲烷氧化过程及其功能菌在碳、氮循环中的生态学功能。     

甲烷厌氧氧化机理及其应用研究进展

甲烷是一种重要的温室气体, 研究证明甲烷厌氧氧化(AOM)对于降低全球甲烷的排放有着重要意义。参与AOM 反应的最终电子受体可分为三类, 即SO2– 4、NO₂^– /NO₃^–以及以Fe³⁺、Cr⁵⁺等为代表的金属离子。本文基于甲烷厌氧氧化过程所利用的电子受体的差别, 结合不同类型AOM 反应微生物的基因型分析, 阐述了AOM 过程的反应机理、相关的微生物种类及其代谢途径。其中对AAA(AOM-associated archaea, 属于ANME-2d)的分离培养, 以及其利用硝酸盐、Fe³⁺、Cr⁵⁺等离子氧化甲烷的研究对认识AOM 反应机理和AOM 的实际应用有很大推动作用。本文还介绍了AOM 过程在环境污染控制领域实际应用中的最新研究进展, 对AOM 的实际应用及其在节能减排上的价值进行展望。AOM 过程的进一步研究对拓宽该过程的工程应用以及对正确认识全球碳、氮、硫循环均有着重要意义。     

微生物介导的甲烷厌氧氧化过程及其影响因子研究进展

温室气体甲烷减排是全球变化领域的研究热点,甲烷厌氧氧化(anaerobic methane oxidation,AOM)过程是一个以前被忽视的甲烷汇,在调控全球甲烷收支平衡及减缓温室效应等方面扮演着十分重要的角色。AOM微生物以甲烷为唯一电子供体,与硫酸盐(SO42-)、亚硝酸盐(NO2-)/硝酸盐(NO3-)、金属离子(Fe3+、Mn4+、Cr6+)等结合完成氧化还原过程,该过程是耦合碳、氮、硫循环的关键环节。本文系统整理分析了不同AOM类型、发生机理、相关功能微生物类群(ANME-1、ANME-2、ANME-3、NC10、MBG-D)及影响AOM过程的关键调控因子的最新研究进展。结果发现,目前80%以上研究都集中在对最常见电子受体类型(SO42-/NO3-/NO2-/Fe3+/Mn4+)的AOM相关过程,而忽视了潜在的新型电子受体(AQDS/HAs O42-/Cr6+/ClO4-等)的耦合作用过程和相对应的微生物类型及作用机理。对未来AOM研究方向提出展望,以期为研究甲烷厌氧氧化菌在不同生态系统中的生态分布及减缓全球温室气体排放提供新的思路。     

微生物厌氧甲烷氧化反硝化研究进展

厌氧甲烷氧化反硝化过程(Denitrifying anaerobic methane oxidation,DAMO)以甲烷为电子供体进行反硝化作用,在实现废水脱氮处理的同时,可有效削减温室气体甲烷的排放,从而减缓全球温室效应。相关机制研究集中在逆向产甲烷途径耦合反硝化和亚硝酸盐依赖型厌氧甲烷氧化(nitrite-dependent anaerobic methane oxidation,n-damo)两个方面。鉴于厌氧甲烷氧化反硝化过程对全球碳氮物质循环的重要意义,本文对近年来厌氧甲烷氧化反硝化过程的研究进展进行了概述,着重阐述了有关厌氧甲烷氧化反硝化微生物富集培养物,特别是含Candidatus Methylomirabilis oxyfera(M.oxyfera)富集培养物的微生物特性、甲烷氧化反硝化的机理以及影响因子。在此基础上,探讨了厌氧甲烷氧化反硝化过程未来的研究方向和工业化应用前景。     

厌氧消化器中的甲烷氧化菌

自产沼气的厌氧消化器中分离到两株甲烷氧化菌。对这类菌在厌氧消化器中的数量变化及其对产甲烷菌生成甲烷活性的影响作了初步探讨。     

厌氧消化器中的甲烷氧化菌

自产沼气的厌氧消化器中分离到两株甲烷氧化菌。对这类菌在厌氧消化器中的数量变化及其对产甲烷菌生成甲烷活性的影响作了初步探讨。     

内陆湿地与水体甲烷厌氧氧化功能微生物研究进展

内陆湿地与水体(如湖泊、河流、水库等)是温室气体甲烷的重要排放源。微生物介导的甲烷厌氧氧化(anaerobic oxidation of methane,AOM)反应在控制内陆湿地与水体甲烷排放中起着不可忽视的作用,对缓解全球温室效应具有重要意义。内陆湿地与水体易形成缺氧环境,且电子受体的种类和数量繁多,是发生AOM反应的理想生境。近年来,不断有研究表明,内陆湿地与水体中存在多种电子受体(NO₂^-、NO₃^-、SO₄^2-、Fe (III)等)驱动的AOM途径。NC10门细菌和甲烷厌氧氧化古菌(anaerobic methanotrophic archaea,ANME)的一新分支ANME-2d主导了湿地和水体环境中的AOM反应,其中ANME-2d具有根据环境条件选择不同电子受体的潜力。研究系统综述了内陆湿地与水体中不同电子受体驱动的AOM途径及其参与的主要功能微生物类群;分析了AOM反应在控制温室气体甲烷排放中的作用及其环境影响因素;总结了相关功能微生物的分子生物学检测方法及甲烷厌氧氧化活性测定的同位素示踪技术。最后,对未来相关研究方向进行了展望。     

水生生态系统中金属依赖型甲烷厌氧氧化过程的研究进展

甲烷是一种比CO_2更活跃的温室气体,微生物驱动的甲烷厌氧氧化(anaerobicoxidationof methane,AOM)过程对于降低全球甲烷的排放有着重要意义。参与AOM反应的最终电子受体主要分为三类,即硫酸盐、亚硝酸盐/硝酸盐以及以Fe(III)、Mn(IV)等为代表的金属离子。可溶性金属物质和不溶性金属矿物都可以被用作AOM的电子受体,这大大提高了参与金属依赖型甲烷厌氧氧化(metal-dependent anaerobic oxidation of methane,Metal-AOM)微生物的生态价值。目前研究聚焦在功能菌群、生态分布等方面。部分甲烷厌氧氧化古菌(anaerobic methanotrophic archaea,ANME)具有直接或间接参与Metal-AOM过程的能力。但由于功能菌群纯化富集和分离具有一定难度,有关其生理生化和生态学等特征的研究受到限制。同时,随着Metal-AOM被发现存在于不同水生生境中,其在污染治理领域的应用也被广泛讨论,但是河口生境尚缺乏深入研究。本文从Metal-AOM的发现入手,阐述了参与该过程的主要微生物及其在水域环境下的生态分布,并介绍了Metal-AOM的反应机制和在实际应用中的机遇与挑战。最后,根据现有研究结果,提出对功能菌群、机制及环保应用的研究展望,包括微生物分离纯化和影响因素、菌群代谢活性和作用机制的解析以及新型生产工艺的设计和发展应用,以期为今后的环境污染治理和工业应用提供借鉴意义。     

厌氧甲烷氧化微生物物质代谢与能量代谢研究进展

甲烷既是一种温室气体,也是一种潜在的能源物质,其源与汇的平衡对地球化学循环及工程应用均有重要意义。厌氧甲烷氧化(anaerobic oxidation of methane,AOM)过程是深海、湿地和农田等自然生境中重要的甲烷汇,在缓解温室气体排放方面发挥了巨大作用。AOM微生物的中枢代谢机制及其能量转化途径则是介导厌氧甲烷氧化耦合其他物质还原的关键所在。因此,本文从电子受体多样性的视角,主要分析了硫酸盐型,硝酸盐/亚硝酸盐型,金属还原型厌氧甲烷氧化微生物的生理生化过程及环境分布,并对近些年发现的新型厌氧甲烷氧化进行了梳理;重点总结了厌氧甲烷氧化微生物细胞内电子传递路径以及胞外电子传递方式;根据厌氧甲烷氧化微生物环境分布及反应特征,就其生态学意义及在污染治理与能源回收方面的潜在应用价值进行了展望。本综述以期深化对厌氧甲烷氧化过程的微生物学认知,并为其潜在的工程应用方向提供新的思路。     

硝酸盐和硫酸盐厌氧氧化甲烷途径及氧化菌群

甲烷属于温室气体,厌氧氧化甲烷有效地减少了大气环境中甲烷的含量。依据吉布斯自由能变,以SO42、Mn4+、Fe3+、NO3等作为电子受体,厌氧条件下甲烷可以转化为CO2。重点阐述以SO42和NO3为电子受体时甲烷厌氧氧化的机理、反应发生的环境条件以及甲烷厌氧氧化菌的特点。针对目前研究存在的主要问题,提出了今后的发展方向。SO42为电子受体时,甲烷厌氧氧化的可能途径包括:逆甲烷生成途径、乙酰生成途径以及甲基生成途径。甲烷的好氧或厌氧氧化协同反硝化是以NO3为电子受体的甲烷氧化的可能途径。环境中的甲烷、硫酸盐或硝酸盐的浓度,有机质的数量,以及环境条件对甲烷的厌氧氧化有显著影响。     

氮依赖型甲烷厌氧氧化菌的整合

氮依赖型甲烷厌氧氧化菌(nitrite-dependent anaerobic methane oxidation bacteria,n-damo细菌,属于NC10门)是最近10年来微生物生态学领域的研究热点。然而,对该类群基于现有数据的生态分布、群落结构和系统进化的整合分析还未见报道。【目的】为了更好地将近年来针对该类群的研究做一次全面梳理,本文通过整合前人已有发表数据和结合自身实验数据两方面进行。【方法】一方面,利用NCBI数据库(数据搜集到2016年11月)中所有n-damo细菌序列对其进行生物信息学分析;另一方面,对大九湖泥炭地表层泥炭利用16S rRNA二代测序技术对该类群进行检测,并同前人数据进行对比。【结果】n-damo细菌主要在沉积物、湿地和水稻土检出;基于pmo A基因的n-damo细菌的平均检出率是基于16S rRNA基因检出率的7倍,但是这两类基因分子标记物所得到的多样性指数保持相对稳定(1.4-3.4);贫氮的大九湖泥炭其NC10的丰度仅为0.067%。【结论】n-damo类群种群相对稳定,暗示其行使的生态功能相对单一;贫氮的大九湖泥炭其极低的NC10丰度暗示氮对NC10是限制因子;具有真正氮依赖型甲烷厌氧氧化细菌的Group A可能只占很少的一部分(小于20%),暗示出该类群真正的生态潜能需要进一步评估。本次整合分析为更好的理解n-damo细菌的生活环境、评估不同基因分子标记物下n-damo细菌的检出率、不同亚类群比如Group A和Group B等的丰度和真正的潜在生态功能提供参考。     

Biogeochemistry and microbial ecology of methane oxidation in anoxic environments: a review

Evidence supporting a key role for anaerobic methane oxidation in the global methane cycle is reviewed. Emphasis is on recent microbiological advances. The driving force for research on this process continues to be the fact that microbial communities intercept and consume methane from anoxic environments, methane that would otherwise enter the atmosphere. Anaerobic methane oxidation is biogeochemically important because methane is a potent greenhouse gas in the atmosphere and is abundant in anoxic environments. Geochemical evidence for this process has been observed in numerous marine sediments along the continental margins, in methane seeps and vents, around methane hydrate deposits, and in anoxic waters. The anaerobic oxidation of methane is performed by at least two phylogenetically distinct groups of archaea, the ANME-1 and ANME-2. These archaea are frequently observed as consortia with sulfate-reducing bacteria, and the metabolism of these consortia presumably involves a syntrophic association based on interspecies electron transfer. The archaeal member of a consortium apparently oxidizes methane and shuttles reduced compounds to the sulfate-reducing bacteria. Despite recent advances in understanding anaerobic methane oxidation, uncertainties still remain regarding the nature and necessity of the syntrophic association, the biochemical pathway of methane oxidation, and the interaction of the process with the local chemical and physical environment. This review will consider the microbial ecology and biogeochemistry of anaerobic methane oxidation with a special emphasis on the interactions between the responsible organisms and their environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coupled anaerobic methane oxidation and metal reduction in soil under elevated CO2

Continued current emissions of carbon dioxide (CO₂) and methane (CH₄) by human activities will increase global atmospheric CO₂ and CH₄ concentrations and surface temperature significantly. Fields of paddy rice, the most important form of anthropogenic wetlands, account for about 9% of anthropogenic sources of CH₄. Elevated atmospheric CO₂ may enhance CH₄ production in rice paddies, potentially reinforcing the increase in atmospheric CH₄. However, what is not known is whether and how elevated CO₂ influences CH₄ consumption under anoxic soil conditions in rice paddies, as the net emission of CH₄ is a balance of methanogenesis and methanotrophy. In this study, we used a long-term free-air CO₂ enrichment experiment to examine the impact of elevated CO₂ on the transformation of CH₄ in a paddy rice agroecosystem. We demonstrate that elevated CO₂ substantially increased anaerobic oxidation of methane (AOM) coupled to manganese and/or iron oxides reduction in the calcareous paddy soil. We further show that elevated CO₂ may stimulate the growth and metabolism of Candidatus Methanoperedens nitroreducens, which is actively involved in catalyzing AOM when coupled to metal reduction, mainly through enhancing the availability of soil CH₄. These findings suggest that a thorough evaluation of climate-carbon cycle feedbacks may need to consider the coupling of methane and metal cycles in natural and agricultural wetlands under future climate change scenarios.     

Enhancing mainstream nitrogen removal by employing nitrate/nitrite-dependent anaerobic methane oxidation processes

Due to serious eutrophication in water bodies, nitrogen removal has become a critical stage for wastewater treatment plants (WWTPs) over past decades. Conventional biological nitrogen removal processes are based on nitrification and denitrification (N/DN), and are suffering from several major drawbacks, including substantial aeration consumption, high fugitive greenhouse gas emissions, a requirement for external carbon sources, excessive sludge production and low energy recovery efficiency, and thus unable to satisfy the escalating public needs. Recently, the discovery of anaerobic ammonium oxidation (anammox) bacteria has promoted an update of conventional N/DN-based processes to autotrophic nitrogen removal. However, the application of anammox to treat domestic wastewater has been hindered mainly by unsatisfactory effluent quality with nitrogen removal efficiency below 80%. The discovery of nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) during the last decade has provided new opportunities to remove this barrier and to achieve a robust system with high-level nitrogen removal from municipal wastewater, by utilizing methane as an alternative carbon source. In the present review, opportunities and challenges for nitrate/nitrite-dependent anaerobic methane oxidation are discussed. Particularly, the prospective technologies driven by the cooperation of anammox and n-DAMO microorganisms are put forward based on previous experimental and modeling studies. Finally, a novel WWTP system acting as an energy exporter is delineated.     

微生物甲烷氧化反硝化耦合反应研究进展

甲烷氧化反硝化耦合过程是连接碳循环和氮循环的重要桥梁.该过程的深入研究有助于完善人们对全球碳氮生物化学循环的认识.甲烷作为反硝化外加气体碳源,既能调控大气甲烷平衡,有效减缓由甲烷引起的温室效应,又能降低反硝化工艺中因投入外加碳源带来的成本.因此近年来甲烷氧化反硝化耦合反应及其机理研究倍受关注.本文主要讨论了好氧和厌氧两种类型的甲烷氧化反硝化过程,重点对其微生物耦合反应机理及其影响因素进行了综述,同时指出了其工程化应用存在的问题,并对其应用前景提出展望.
     

硝态氮还原型厌氧甲烷氧化的研究进展及展望

以硝态氮为电子受体的甲烷厌氧氧化(Nx-damo)是近年被证实的微生物驱动的地球氮、碳循环机制,对于认识重要元素地球化学循环的微生物驱动机制和自然环境中甲烷的源与汇具有重大意义;在废水生物脱氮及其温室气体减排方面也具有潜在工程应用价值。从功能微生物富集及其影响因素、生理特性、生物代谢的可能机理等方面对Nx-damo的最新进展进行了梳理和讨论;评估了其应用于废水处理的潜力和优势;对未来的研究方向进行了展望,以期推动该领域更广泛的研究,并为其提供有价值的参考。     

Thermophilic anaerobic oxidation of methane by marine microbial consortia

The anaerobic oxidation of methane (AOM) with sulfate controls the emission of the greenhouse gas methane from the ocean floor. AOM is performed by microbial consortia of archaea (ANME) associated with partners related to sulfate-reducing bacteria. In vitro enrichments of AOM were so far only successful at temperatures ⩽25 °C; however, energy gain for growth by AOM with sulfate is in principle also possible at higher temperatures. Sequences of 16S rRNA genes and core lipids characteristic for ANME as well as hints of in situ AOM activity were indeed reported for geothermally heated marine environments, yet no direct evidence for thermophilic growth of marine ANME consortia was obtained to date. To study possible thermophilic AOM, we investigated hydrothermally influenced sediment from the Guaymas Basin. In vitro incubations showed activity of sulfate-dependent methane oxidation between 5 and 70 °C with an apparent optimum between 45 and 60 °C. AOM was absent at temperatures ⩾75 °C. Long-term enrichment of AOM was fastest at 50 °C, yielding a 13-fold increase of methane-dependent sulfate reduction within 250 days, equivalent to an apparent doubling time of 68 days. The enrichments were dominated by novel ANME-1 consortia, mostly associated with bacterial partners of the deltaproteobacterial HotSeep-1 cluster, a deeply branching phylogenetic group previously found in a butane-amended 60 °C-enrichment culture of Guaymas sediments. The closest relatives (Desulfurella spp.; Hippea maritima) are moderately thermophilic sulfur reducers. Results indicate that AOM and ANME archaea could be of biogeochemical relevance not only in cold to moderate but also in hot marine habitats.