氮肥对土壤氧化大气甲烷影响的机制

综合评述了氮素对土壤氧化甲烷的抑制机制。包括 :( 1)竞争甲烷单氧化酶的竞争抑制机制 ,( 2 )代谢产物的毒害抑制机制 ,( 3)外源盐引起的微生物生理缺水抑制机制和 ( 4)氮素周转作用引起的抑制机制。提出了氧化菌竞争利用土壤空气有限O2 的竞争抑制机制 ,即氨氧化菌利用更多的土壤有限氧气→产生优势氨氧化菌→形成优势菌群→限制甲烷氧化菌繁殖和功能发挥的氨长期抑制土壤氧化大气甲烷的机制 ,并认为这种抑制作用是不可逆的     

环境胁迫对氨氧化菌群的影响研究进展

土壤污染物具有隐蔽性、滞后性、难治理性等特点,长期影响着土壤生态环境的安全,如何全面、实时地监测土壤环境质量成为当今的研究热点.氮素转化过程是元素地球化学循环中对土壤污染和质量十分敏感的代谢过程.硝化作用是氮素转化的主要过程之一,从硝化作用的限速步骤——氨氧化过程为切入点,综述环境条件如pH、铵浓度、O_2浓度、有机质含量、温度、季节等对氨氧化细菌(ammonia-oxidizing bacteria,AOB)和氨氧化古菌(ammonia-oxidizing archaea,AOA)的生理生化性质、转录水平和群落结构的影响,以及利用分子生物学方法测定氨氧化菌群结构及其功能基因表达量用于反映环境变化的应用前景.微生物在酶的协同作用下完成氨氧化作用;目前对氨氧化菌群群落结构的研究对象主要为16S rRNA基因和amoA功能基因;在不同的生态环境条件下,氨氧化古菌比氨氧化细菌的分布更广,且在同一环境因子胁迫下,AOB和AOA的响应有所不同,AOA在低温、低铵浓度、酸性等寡营养条件下更为活跃,AOB则在高铵浓度、碱性等条件下更为活跃,这表明二者在不同的环境条件下对硝化作用的贡献不同.最后对氨氧化菌群群落结构以及氨氧化相关基因表达水平在揭示环境变化方面进行了展望,认为未来对氨氧化微生物代谢关键酶的基因表达信息、AOA和AOB变化规律与环境因子之间的相关性进行深入研究是非常有必要的.(图1表1参82)     

影响厌氧氨氧化与甲烷化反硝化耦合的因素

氨氮、氮氧化物对产甲烷菌有一定的抑制作用,但可以通过驯化去除毒性.亚硝酸盐在厌氧氨氧化菌作用下与氨发生厌氧氨氧化反应.虽然厌氧氨氧化菌是自养菌,但具有异养代谢能力,并且NO2可提高厌氧氨氧化菌的活性.因此,通过特殊的反应器技术,将厌氧氨氧化菌与甲烷菌、反硝化菌复合在一个有利的微生态环境中,充分发挥它们之间的协同耦合作用,把有机物转化为清洁能源又同时脱氮,是极有前景的废水厌氧(缺氧)处理研究新方向.表1参31     

接种污泥源对厌氧氨氧化启动效能的影响

厌氧氨氧化(anaerobic ammonium oxidation,ANAMMOX)菌生长缓慢是影响其实际应用的主要问题之一,选取合适的接种污泥十分重要.本研究采用好氧污泥、厌氧颗粒污泥和厌氧消化污泥3种接种污泥,分别经过61、70和85 d的运行均实现了厌氧氨氧化过程,氨氮去除率分别为82%、92%和91%,总氮去除率达76%、82%和80%.分别接种3种污泥源的厌氧序批式反应器(ASBR)R1、R2、1t3出水pH值最终稳定在8.4、8.5、8.5.好氧污泥呈絮状,但沉降性比接种前好,厌氧颗粒污泥解体后最终形成粒径集中在0.5～1.0 mm的污泥,厌氧消化污泥则呈沙化状态,有细小颗粒出现.根据厌氧氨氧化细胞产率系数及NH4+-N、NO2--N去除量和NO3--N生成量之间的计量学关系,估算出厌氧氨氧化菌产率系数(以1 mol NH4+产生的CH2O0.5N0.15量计)分别为0.080、0.105和0.114 mol·mol-1,说明反应器内厌氧氨氧化菌有不同程度的衰减.总体而言,厌氧颗粒污泥是富集厌氧氨氧化菌的最适污泥源.     

高氨氮废水处理系统中功能微生物的检测

利用16S rDNA分子检测技术对高氨氮废水处理系统中的氨氧化细菌、亚硝酸盐氧化细菌等难分离培养微生物进行了分析检测.从实验室处理高氨氮废水的生物流化床硝化系统生物膜中提取细菌总DNA,以其为模板,利用氨氧化细菌(AOB)和亚硝酸盐氧化细菌(NOB)的16S rDNA特异性引物进行多聚酶链式反应(PCR)扩增,获得AOB和NOB的特异片段.将特异片段与pGEM-T载体连接并转化到E.coli DH5α中获得重组子,对阳性重组子进行酶切分型,AOB可分为8种不同类型.选取AOB的8种类型代表以及随即选取8个NOB克隆进行测序.经GenBank搜索以及同源性分析,发现所获得的8个AOB类型来自不同的菌株,处理系统中以Nitrosomonas sp.和Nitrosococcus sp.为氨氧化细菌的优势菌属;8株NOB重组子中有7株来自不同的菌株,系统中Nitrobacter sp.和Afipia sp.为亚硝酸盐氧化细菌的优势菌属.图6表1参14     

氮肥对土壤氧化大气甲烷影响的机制

综合评述了氮氧化甲烷的抑制机制。包括：（1）竞争甲烷单氧化酶的竞争抑制机制，（2）代谢产物的毒害抑制机制，（3）外源盐引起的微生物生理缺水抑制机制和（4）氮素周围作用引起的抑制机制。提出了氧化菌竞争利用土壤空气有限O2的竞争抑制机制，即氨氧化菌利用更多的土壤有限氧气→产生优势氨氧化菌→形成优势菌群→限制甲烷氧化菌繁殖和功能发挥的氨长期抑土壤化大气甲烷的机制，并认为这种抑制作用是不可逆的。     

厌氧氨氧化反应器研究进展

厌氧氨氧化是废水生物脱氮研究的新领域,厌氧氨氧化反应器影响厌氧氨氧化菌的富集、厌氧氨氧化过程的启动、运行的稳定性和处理效果,是其中十分重要的研究内容.本文根据厌氧氨氧化反应的基本特征,分析了反应过程对反应器的主要要求;通过对固定床反应器、流化床反应器、气提式反应器、上流式厌氧污泥床(UASB)等反应器的运行参数和运行结果的比较,分析了各种类型反应器的主要优缺点,并对反应器今后的发展方向提出了建议.表2参37     

厌氧氨氧化菌的种类、特性与检测

厌氧氨氧化是地球氮素循环的重要环节,也是废水生物脱氮和污染环境修复的重要基础;厌氧氨氧化菌作为厌氧氨氧化功能的执行者,近年来成为微生物、环境、地学等领域的研究热点.本文从厌氧氨氧化菌种类、菌种特性及检测手段3个方面综述近年国内外厌氧氨氧化菌研究进展.基于多相分类法,以遗传型分类为主,目前共鉴定厌氧氨氧化菌6属21种,其中Candidatus Anammoximicrobium为最新属.不同种厌氧氨氧化菌在形态结构、细胞组成、生理生化、生态分布存在异同,对温度、盐度、有机物等环境因素的敏感度导致其生态位的差异性,有利于工程应用.近来结合PCR-DGGE、FISH和q PCR等先进的现代分子生物学手段,已形成一套研究厌氧氨氧化菌种类、数量、分布和活性的有效方法,并获得系列基于An AOB 16S r RNA及功能基因(nir S,hzo)的特异性引物.最后提出完善厌氧氨氧化菌纯培物的分离方法、探明厌氧氨氧化菌的代谢途径和遗传特性、明确厌氧氨氧化菌在生境中的分布及贡献是未来研究的热点和难点.     

Mn(Ⅱ)氧化细菌的微生物学研究进展

Mn(Ⅱ)氧化细菌广泛存在于自然界中,对其生理特性、氧化机制和功能等的研究,对于进行含锰水处理过程中生物除锰机理的探究具有重大意义.本文就国内外对Mn(Ⅱ)氧化细菌的氧化机理、酶学研究等进展进行了总结.普遍认为,Mn(Ⅱ)的氧化机理可分为:(1)间接氧化,即微生物通过新陈代谢作用改变自身微环境,如pH、Eh,从而实现Mn(Ⅱ)的化学氧化;(2)直接氧化,即锰氧化酶的直接催化氧化或通过特定的键合作用实现氧化.目前酶学研究中所涉及到的酶有:木质素过氧化酶、锰过氧化物酶、漆酶、木质素降解酶等,所涉及到的微生物有:生盘纤发菌、杆状菌、土微菌属、假单胞菌、真菌等.本文同时也提出了Mn(Ⅱ)氧化细菌的微生物学研究中存在的问题,对进一步的研究作了展望.表1参45     

祁连山冻土区土壤活动层与冻土层中甲烷代谢微生物群落结构特征

冻土土壤中的甲烷代谢微生物可氧化或产生甲烷,影响着甲烷所参与的碳循环过程,对于全球温室气体的释放和调节具有重要的作用.对祁连山冻土区土壤活动层与冻土层中的甲烷代谢微生物产甲烷菌(Methanogens)和甲烷氧化菌(Methanotrophs)的群落结构组成进行研究.通过对产甲烷菌的mcrA基因和甲烷氧化菌的pmoA基因进行PCR扩增,分别构建其基因克隆文库,并通过序列同源比对进行系统发育分析和多样性分析.结果显示:冻土土壤活动层中的产甲烷菌包括Rice cluster Ⅰ、Methanosarcinaceae、Methanomicrobiales、Methanosaetaceae、Methanobacteriaceae五种类型,而在土壤冻土层则包括了Rice cluster Ⅰ、Methanosarcinaceae、Methanobacteriaceae三种类型.土壤活动层的甲烷氧化菌由隶属于α-Proteobacteria(Type Ⅱ)的Methylocystis和隶属于γ-Proteobacteria(Type Ⅰ)的Methylobacter两种类型群体组成,而土壤冻土层中则只包括了Methylocystis这一种类型.由此可见,冻土土壤活动层与冻土层中的甲烷代谢微生物群落结构存在一定的差异.     

沣河水系脱氮微生物群落结构研究

河流水体氮素的超负荷不仅破坏了水体生态环境,也严重威胁着人类的生存和发展.水体中有机氮、无机氮（氨氮、亚硝氮、硝氮）和分子氮之间的转化（氮循环）有赖于水体中大量的氮循环微生物（固氮细菌、硝化细菌和反硝化细菌）,然而这些氮循环微生物的生长繁殖也受到包括氮素的形态和浓度在内的多种环境因子的影响,这些因素也通过影响氮循环微生物的生长繁殖进而使得水体中氮素的转化速率发生变化,对水体氮污染的防治有不可忽视的作用.本研究通过在沣河设置不同的研究断面,采集水体样品,进行水质分析,并通过现代分子生物学技术（PCR-DGGE）方法对研究断面水体中氮循环微生物（固氮细菌、硝化细菌和反硝化细菌）的群落结构进行分析.再通过统计学软件对所得分子生物学信息与水质环境因子的相关性进行统计学分析,发现沣河水体中氮循环微生物群落结构受到多种环境因子共同影响,且在枯水期和丰水期表现出不同的特征.在丰水期沣河水体中,硝化细菌群落在中游表现出较高的多样性和丰富性,这与沣河中上游农业COD（化学需氧量）、BOD（生化需氧量）氨氮及有机氮污染物排放量较大,沣河水体DO（溶解氧）高有关.水体中的氨氮、亚硝氮、温度的增加是促进水体中硝化细菌的均匀性和丰富度的增高的主要因子,而pH 值的升高,使得水体中硝化细菌的均匀性和丰富度降低.反硝化微生物在中游和下游的多样性和丰富度较高,与有机物及硝酸盐含量相关.水体中的BOD、COD、TP（总磷）、硝氮的增加是促进水体中反硝化细菌的均匀性和丰富度的增高主要相关因子,而DO 的增多则会对部分反硝化细菌产生不利影响,使得水体中反硝化细菌的均匀性和丰富度降低.本研究结果为沣河以及其他河流的污染控制以及基于微生物的生态修复提供了科?     

Overlooked nitrogen-cycling microorganisms in biological wastewater treatment

• AOA and comammox bacteria can be more abundant and active than AOB/NOB at WWTPs. • Coupled DNRA/anammox and NO_x-DAMO/anammox/comammox processes are demonstrated. • Substrate level, SRT and stressors determine the niches of overlooked microbes. • Applications of overlooked microbes in enhancing nitrogen removal are promising. Nitrogen-cycling microorganisms play key roles at the intersection of microbiology and wastewater engineering. In addition to the well-studied ammonia oxidizing bacteria, nitrite oxidizing bacteria, heterotrophic denitrifiers, and anammox bacteria, there are some other N-cycling microorganisms that are less abundant but functionally important in wastewater nitrogen removal. These microbes include, but not limited to ammonia oxidizing archaea (AOA), complete ammonia oxidation (comammox) bacteria, dissimilatory nitrate reduction to ammonia (DNRA) bacteria, and nitrate/nitrite-dependent anaerobic methane oxidizing (NO_x-DAMO) microorganisms. In the past decade, the development of high-throughput molecular technologies has enabled the detection, quantification, and characterization of these minor populations. The aim of this review is therefore to synthesize the current knowledge on the distribution, ecological niche, and kinetic properties of these “overlooked” N-cycling microbes at wastewater treatment plants. Their potential applications in novel wastewater nitrogen removal processes are also discussed. A comprehensive understanding of these overlooked N-cycling microbes from microbiology, ecology, and engineering perspectives will facilitate the design and operation of more efficient and sustainable biological nitrogen removal processes.     

Impact of total organic carbon and chlorine to ammonia ratio on nitrification in a bench-scale drinking water distribution system

Nitrification occurs in chloraminated drinking water systems and is affected by water quality parameters. The aim of this study was to investigate the impact of total organic carbon and chlorine to ammonia ratio on nitrification potential in a simulated drinking water distribution system as during chloramination. The occurrence of nitrification and activity of nitrifying bacteria was primarily monitored using four rotating annular bioreactors (RAB) with different chlorine to ammonia ratios and total organic carbon (TOC) levels. The results indicated that nitrification occurred despite at a low influent concentration of ammonia, and a high concentration of nitrite nitrogen was detected in the effluent. The study illustrated that reactors 1(R1) and 3 (R3), with higher TOC levels, produced more nitrite nitrogen, which was consistent with the ammonia-oxidizing bacteria (AOB) counts, and was linked to a relatively more rapid decay of chloramines in comparison to their counterparts (R2 and R4). The AOB and HPC counts were correlated during the biofilm formation with the establishment of nitrification. Biofilm AOB abundance was also higher in the high TOC reactors compared with the low TOC reactors. The chlorine to ammonia ratio did not have a significant impact on the occurrence of nitrification. Bulk water with a high TOC level supported the occurrence of nitrification, and AOB development occurred at all examined chlorine to ammonia dose ratios (3:1 or 5:1).     

Differences in distributions,assembly mechanisms,and putative interactions of AOB and NOB at a large spatial scale

● Nitrifiers in WWTP were investigated at large spatial scale. ● AOB populations varied greatly but NOB populations were similar among cities. ● Drift dominated both AOB and NOB assembling processes. ● DO did not show a significant effect on NOB. ● NOB tended to cooperate with AOB and non-nitrifying microorganisms. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) play crucial roles in removing nitrogen from sewage in wastewater treatment plants (WWTPs) to protect water resources. However, the differences in ecological properties and putative interactions of AOB and NOB in WWTPs at a large spatial scale remain unclear. Hence, 132 activated sludge (AS) samples collected from 11 cities across China were studied by utilizing 16S rRNA gene sequencing technology. Results indicated that Nitrosomonas and Nitrosospira accounted for similar ratios of the AOB community and might play nearly equal roles in ammonia oxidation in AS. However, Nitrospira greatly outnumbered other NOB genera, with proportions varying from 94.7% to 99.9% of the NOB community in all WWTPs. Similar compositions and, hence, a low distance–decay turnover rate of NOB (0.035) across China were observed. This scenario might have partly resulted from the high proportions of homogenizing dispersal (~13%). Additionally, drift presented dominant roles in AOB and NOB assembling mechanisms (85.2% and 81.6% for AOB and NOB, respectively). The partial Mantel test illustrated that sludge retention time and temperature were the primary environmental factors affecting AOB and NOB communities. Network results showed that NOB played a leading role in maintaining module structures and node connections in AS. Moreover, most links between NOB and other microorganisms were positive, indicating that NOB were involved in complex symbioses with bacteria in AS.     

Biological production of nitrite in seawater

The relative importance of 3 different sources for biological production of nitrite in seawater was studied. Decomposition of fecal pellets of the copepod Calanus helgolandicus (at a concentration of approximately 12 g-at N/l), in seawater medium, released small amounts of ammonia over a 6 week period. It nitrifying bacteria were added to the fecal pellets nitrite was barely detectable over the same period. Decomposition of phytoplankton (present at a concentration of about 8 g-at particulate plant N/l) with added heterotrophic bacteria, released moderate amounts of ammonia over a 12 week period. If the ammonia-oxidizing bacterium Nitrosocystis oceanus was added to the decomposing algae, nitrite was produced at a rate of 0.2 g-at N/l/week. Heterotrophic nitrification was not observed when 7 open-ocean bacteria were tested for their ability to oxidize ammonia. The diatom Skeletonema costatum, either non-starved or starved of nitrogen, produced nitrite when growing with 150 or 50 g-at NO ₂ ^- -N/l at a light intensity of about 0.01 ly/min. When nitrate in the medium was exhausted, S. costatum assimilated nitrite. If starved of vitamin B₁₂, both non-N-starved and N-starved cells of S. costatum produced nitrite in the medium with 150 g-at NO ₃ ^- -N/l. Nitrate was not exhausted and cell densities reached 2x10⁵/ml due to vitamin B₁₂ deficiency. If light intensity was reduced to 0.003 ly/min under otherwise similar conditions, cells did not grow due to insufficient light, and nitrite was not produced. In the sea, it appears that, in certain micro-environments, decomposition of particulate matter releases ammonia with its subsequent oxidation to nitrite. The amounts of these nutrients and the rate at which they are produced are dependent upon the nature of the materials undergoing decomposition and the associated bacteria. In certain other areas of the sea, where phytoplankton standing stock is high and nitrate is non-limiting, excretion by these organisms is a major source of nitrite.     

铁循环微生物对环境中重金属的影响研究进展

铁循环微生物包括铁氧化菌(Fe(Ⅱ)-oxidizing bacteria,FeOB)和铁还原菌(Fe(Ⅲ)-reducing bacteria,FeRB),在由它们介导Fe²⁺(Fe³⁺)氧化(还原)的过程中,往往也伴随着一系列重金属元素的迁移转化,对重金属在环境中的生物有效性和迁移性方面有重要作用.本文综述了环境中的铁循环微生物,针对铁循环微生物驱动重金属迁移转化的作用机制,分别从铁氧化菌氧化亚铁生成铁矿物对重金属的固定,铁还原菌介导铁矿物还原溶解及次生矿物生成,以及铁循环微生物代谢耦合重金属形态转化方面进行阐述;进一步通过研究实例综述了铁循环微生物对环境中砷、镉、铬、铜、铅等重金属的作用及修复潜力;未来的研究可关注特定微生物的成矿机制,生物成矿对重金属固定的调控,以及重金属复合污染场地的铁循环微生物修复应用等方面.本文以期为基于铁循环微生物的重金属污染修复提供理论指导和应用依据.     

Visible light induces bacteria to produce superoxide for manganese oxidation

● Term of manganese-oxidizing microorganisms should be reconsidered. ● Visible light induces heterotrophic bacteria to produce superoxide. ● Heterotrophic bacteria oxidize Mn(II) ions with a fast oxidation rate. ● Superoxide oxidizing Mn(II) ions is an unintended side reaction of bacteria. ● Superoxide is an important oxidation force of Mn(II) in the environment. Manganese oxides are widely distributed in soils and sediments, affecting the migration and transformation of heavy metals and organic pollutants. The microbial conversion of soluble Mn(II) into insoluble Mn(III/IV) oxides is considered to be the initial source of manganese oxides in the environment; however, whether this process is related to a physiological role remains unclear. Here, we explored the microbial manganese oxidation process under visible light by using coastal surface seawater microorganisms. Visible light greatly promotes the oxidation rate of Mn(II), and the average rate reaches 64 μmol/(L·d). The generated manganese oxides were then conducive to Mn(II) oxidation, thus the rapid manganese oxidation was the result of the combined action of biotic and abiotic, and biological function accounts for 88 % ± 4 %. Extracellular superoxide produced by microorganisms induced by visible light is the decisive factor for the rapid manganese oxidation in our study. But the production of these superoxides does not require the presence of Mn(II) ions, the Mn(II) oxidation process was more like an unintentional side reaction, which did not affect the growth of microorganisms. More than 70 % of heterotrophic microorganisms in nature are capable of producing superoxide, based on the oxidizing properties of free radicals, all these bacteria can participate in the geochemical cycle of manganese. What’s more, the superoxide oxidation pathway might be a significant natural source of manganese oxide.     

Performance of an ANAMMOX reactor treating wastewater generated by antibiotic and starch production processes

A pilot-scale anaerobic ammonia oxidation (ANAMMOX) reactor was used to treat mixed wastewater resulting from a chlortetracycline and starch production process. The results, collected over the course of 272 days, show that the ratio of influent ammonium to nitrite, pH, and temperature can all affect the efficiency of nitrogen removal. The ratio of influent ammonium to nitrite was maintained at about 1:1 at a concentration below 200 mg·L^-1 for both influent ammonium and nitrite. The total nitrogen (TN) loading rate was 0.15–0.30 kgN·m^-3·d^-1, pH remained at 7.8–8.5, and temperature was recorded at 33±1°C. The rate of removal of ammonia, nitrite, and TN were over 90%, 90%, and 80%, and the effluent ammonium, nitrite and TN concentrations were below 50, 30, and 100 mg·L^-1.     

养殖水体复合功能菌的分离及其性能

针对养殖水体中因氨态氮、硫化氢和小分子有机酸富营养化引起的污染问题,分离筛选出硝化细菌、反硝化细菌、光合细菌、硫化细菌和生物絮凝菌等具有不同生理功能的污染物治理菌株,经优化配伍制备出性能优良的复合功能菌,结果表明:硝化细菌对氨态氮的去除率达97.8%,亚硝态氮的去除率达95.7%,反硝化细菌对硝态氮的去除率为96.4%,光合细菌和硫化细菌对硫化氢的去除率为55%,微生物絮凝菌的絮凝效率为83%;复合功能菌对CODCr、NH4+-N,总氮、硫化物的去除率分别可达94.3%,89.6%,88.7%和71.3%。