Compositional Shifts in Ammonia-Oxidizing Microorganism Communities of Eight Geographically Different Paddy Soils —Biogeographical Distribution of Ammonia-Oxidizing Microorganisms

Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities in a large geographical scale. Here, eight paddy soils collected from different geographic regions in China were selected to investigate the spatial distribution of AOA and AOB, and their potential nitrification activity (PNA). The result showed that the abundance of AOA was predominant over AOB, indicating that the rice fields favor the growth of AOA. PNA highly varied from 0.43 to 3.57 μg NOX-N·g·dry·soil·h-1, and was positively related with soil NH3 content, the abundance of AOA community, and negatively related with the diversity of AOB community (P amoA genes revealed remarkable differences in the compositions of AOA and AOB community. Phylogenetic analyses of amoA genes showed that Nitrosospiracluster-3-like and Nitrosomonas cluster 7-like AOB extensively dominated the AOB communities, and 54d9-like AOA within the soil group 1.1b predominated in AOA communities in paddy soils. Redundancy analysis suggested that the spatial variations of AOA community structure were influenced by soil TN content (P < 0.01), while no significant correlation between AOB community structure and soil properties was found. Findings highlight that ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with N availability.

Seasonal and spatial distribution of ammonia-oxidizing microorganism communities in surface sediments from the East China Sea

Ammonia oxidation plays a significant role in the nitrogen cycle in marine sediments. Seasonal and spatial distribution of ammonia-oxidizing archaea （AOA） and betaproteobacteria （13-AOB） in surface sediments from the East China Sea （ECS） were investigated using ammonia monooxygenase ct subunit （amoA） gene. In order to characterize the community of AOA and 13-AOB, real-time quantitative polymerase chain reaction （qPCR） was carried out in this study, along with environmental parameters. The abundance of 13-AOB amoA gene （2.17x 10^6-4.54x10^7 copy numbers per gram wet weight sediment） was always greater than that ofAOA amoA gene （2.18x 105-9.89x 10^6 copy numbers per gram wet weight sediment） in all sampling stations. The qPCR results were correlated with environmental parameters. AOA amoA gene copy numbers in April were positively related to temperature and nitrite concentration （p〈0.05）. 13-AOB amoA gene copy numbers in August correlated negatively with salinity （p〈0.01）, and correlated positively with ammonium concentration （p〈0.05）. With the increase of salinity, the amoA gene copy ratio of AOB to AOA had a tendency to decrease, which suggested 13-AOB dominated in the area of high level ammonium and AOA preferred high salinity area.

Irrigation water salinity and N fertilization:Effects on ammonia oxidizer abundance, enzyme activity and cotton growth in a drip irrigated cotton field

Use of saline water in irrigated agriculture has become an important means for alleviating water scarcity in arid and semi-arid regions. The objective of this field experiment was to evaluate the effects of irrigation water salinity and N fertilization on soil physicochemical and biological properties related to nitrification and denitrification. A 3×2 factorial design was used with three levels of irrigation water salinity（0.35, 4.61 and 8.04 d S m-1） and two N rates（0 and 360 kg N ha^（-1））. The results indicated that irrigation water salinity and N fertilization had significant effects on many soil physicochemical properties including water content, salinity, p H, NH_4-N concentration, and NO_3-N concentration. The abundance（i.e., gene copy number） of ammonia-oxidizing archaea（AOA） was greater than that of ammonia-oxidizing bacteria（AOB） in all treatments. Irrigation water salinity had no significant effect on the abundance of AOA or AOB in unfertilized plots. However, saline irrigation water（i.e., the 4.61 and 8.04 d S m-1 treatments） reduced AOA abundance, AOB abundance and potential nitrification rate in N fertilized plots. Regardless of N application rate, saline irrigation water increased urease activity but reduced the activities of both nitrate reductase and nitrite reductase. Irrigation with saline irrigation water significantly reduced cotton biomass, N uptake and yield. Nitrogen application exacerbated the negative effect of saline water. These results suggest that brackish water and saline water irrigation could significantly reduce both the abundance of ammonia oxidizers and potential nitrification rates. The AOA may play a more important role than AOB in nitrification in desert soil.

Distribution of ammonia-oxidizing Betaproteobacteria community in surface sediment off the Changjiang River Estuary in summer

The spatial distribution of ammonia-oxidizing Betaproteobacteria （βAOB） was investigated by FISH （fluorescence in situ hybridization） and DGGE （denaturing gradient get electrophoresis） techniques in the sediment off the Changjiang River Estuary. Sediment samples were collected from eight stations in June before the formation of hypoxia zone in 2006. The abundance of βAOB ranged from 1.87× 10^5 to 3.53×10^5 cells/g of sediment. βAOB abundance did not present a negative correlation with salinity, whereas salinity was implicated as the primary factor affecting nitrification rates. The DGGE profiles of PCR-amplified amoA gene fragments revealed that the βAOB community structure of sample S2 separated from other samples at the level of 40% similarity. The variations in composition ofβAOB were significantly correlated with the salinity, temperature, absorption ability of sediments and TOC. The statistical analysis indicates that theβAOB abundance was a main factor to influence nitrification rates with an influence ratio of 87.7% at the level of 40% biodiversity similarity. Considering the good correlation between βAOB abundance and nitrification estimates, the abundance and diversity of βAOB community could be expected as an indirect index of nitrification activity at the study sea area in summer.

Dehydrogenase Activity of Soil Microorganisms and the Total DNA Level in Soil of Different Use

The aim of the study was to find the interrelations between the activity of intracellular dehydrogenases, abundance of microorganisms, and the level of soil DNA in the Mollic Gleysol profile, with notification on the dominant DNA form （extra-or intra-cellular）, depending on the type of land use. Two neighbouring meadows were selected for investigations： one systematically cultivated and fertilized and the other deprived of any effect of anthropogenic activity, used as a control. We have demonstrated that dehydrogenase activity （DHA）, the DNA content and microbial abundance strongly depended on the type of land use. DHA exhibited a significant correlation with the DNA content （r = 0.99^＊＊＊ and r = 0.74^＊, for cultivated and control sites, respectively）. This relationship with such a high r value might suggest domination of the intracellular form of DNA in the cultivated meadow, which is also confirmed by the c.a. 13% increase in microorganism abundance in the cultivated soil. The optimal conditions for microbial activities were defined by the significant positive interrelationships between microbial abundance and the total organic carbon content, and a negative correlation with pH, redox potential and soil bulk density.

橘园绿肥种植对土壤氨氧化微生物的影响

本研究以当阳凤凰山长期定位施肥柑橘试验基地为平台,进行了自然生草(NG)、人工种植光叶苕子(LP)以及光叶苕子混播于自然生草(NL)等三种绿肥处理,通过植物群落调查、土壤理化性质测定,以及qPCR和Illumina Miseq高通量测序的方法,阐明橘园土壤氨氧化微生物AOA和AOB的功能基因丰度和群落结构对不同绿肥种植处理的响应特征,并探讨植物群落和土壤理化因子对它们的影响。研究结果表明:相比于NG,人工种植绿肥(LP和NL)对AOA和AOB数量的影响不一,LP降低了AOA和AOB的amoA基因拷贝数,NL降低了AOA-amoA但增加了AOB-amoA基因拷贝数;LP和NL中AOA的Ace指数和Chao指数显著高于NG,LP中AOB的Shannon指数显著高于NG,三个处理的β多样性差异显著;三种绿肥种植处理下AOA共获得119个OTU,优势门和属分别是泉古菌门和norank—Crenarchaeota,其中norank—Crenarchaeota在NG中的相对丰度显著高于LP和NL;AOB共获得142个OTU,优势门和属分别是变形菌门和亚硝化螺菌属,其中亚硝化螺菌属的相对丰度在不同处理中有显著差异,其LP中最高,为45.87%;Mantel检验和冗余-层次分割分析结果表明,氨氧化微生物的丰度、多样性和组成受到绿肥种植后的植物因子(如群落高度、盖度、多样性、地上生物量和地下生物量、根系碳氮含量等)和土壤因子(如pH、土壤含水量、总碳、总氮、铵态氮、硝态氮和速效磷含量等)的共同影响。该研究说明在橘园种植绿肥可改变地上植物群落特征和土壤理化性质,从而使土壤中氨氧化微生物的数量和群落结构发生变化,其中光叶苕子混播于自然生草的生草模式可明显增加土壤氨氧化微生物量,促进土壤的硝化作用和改善果园生态环境,因此,实际应用中可优先考虑此模式。

活性污泥萃取液施用对水稻根际土壤微生物群落结构的影响

通过根箱试验,从土壤根际微生物角度揭示活性污泥萃取液(简称萃取液)调控水稻苗期生长和改良土壤理化性质的机理。试验设计不同萃取液配施减氮处理(T1,空白对照;T2,常规施肥对照;T3,减氮30%配施0.2 g/kg萃取液;T4,减氮30%配施0.4 g/kg萃取液;T5,施用8 g/kg萃取液全量替代化肥氮,即减氮75%),研究萃取液配合氮肥减施对水稻根际土壤理化性质和微生物群落结构的影响。结果表明:配施萃取液可显著增加水稻幼苗的叶面积、生物量和叶绿素含量;与常规施肥相比,配施萃取液可以显著提高土壤p H,降低土壤电导率,增加可溶性有机碳含量,降低硝态氮和铵态氮含量。β多样性结果显示,萃取液对土壤微生物性质的影响主要作用在根际及近根际土壤中,不同萃取液处理组与空白及常规施肥对照组间细菌群落结构及多样性存在显著性差异(P<0.05);萃取液的施用可增加有机污染物降解和碳水化合物代谢相关微生物的相对丰度,如黄色土源菌、Candidatus_Udaeobacter、鞘氨醇单胞菌属,相对丰度分别增加151%~541%、26%~320%和55%~364%。采用FAPROTAX土壤功能预测分析发现,施用萃取液后土壤菌群主要增加的功能为化能异养、有氧化能异养、硝酸盐还原、固氮作用、硝化作用和芳香化合物降解等,这类功能与土壤碳源物质代谢、氮循环及有机污染物降解等行为相关。萃取液施用可通过改善土壤根际及近根际微生物群落结构,增加相关菌群丰度,调控土壤根际及近根际碳、氮循环,进而达到促进水稻幼苗生长和土壤改良的效果。研究结果可为活性污泥的资源化提供新路径。

Abundance and composition of ammonia-oxidizing bacteria and archaea in different types of soil in the Yangtze River estuary

Tidal flats are soil resources of great significance.Nitrification plays a central role in the nitrogen cycle and is often a critical first step in nitrogen removal from estuarine and coastal environments.We determined the abundance as well as composition of ammonia-oxidizing bacteria(AOB) and ammonia-oxidizing archaea(AOA) in different soils during land reclamation process.The abundance of AOA was higher than that of AOB in farm land and wild land while AOA was not detected in tidal flats using real-time polymerase chain reaction(PCR).The different abundances of AOB and AOA were negatively correlated with the salinity.The diversities of AOB and AOA were also investigated using clone libraries by amplification of amoA gene.Among AOB,nearly all sequences belonged to the Nitrosomonas lineage in the initial land reclamation process,i.e.,tidal flats,while both Nitrosomonas and Nitrosospira lineages were detected in later and transition phases of land reclamation process,farm land and wild land.The ratio of the numbers of sequences of Nitrosomonas and Nitrosospira lineages was positively correlated with the salinity and the net nitrification rate.As for AOA,there was no obvious correlation with the changes in the physicochemical properties of the soil.This study suggests that AOB may be more import than AOA with respect to influencing the different land reclamation process stages.

Abundance and diversity of ammonia-oxidizing archaea in response to various habitats in Pearl River Delta of China, a subtropical maritime zone

Ammonia-oxidizing archaea （AOA） are widely considered key to ammonia oxidation in various environments. However, little work has been conducted to simultaneously investigate the abundance and diversity of AOA as well as correlations between archaeal amoA genotypes and environmental parameters of different ecosystems at one district. To understand the abundance, diversity, and distribution of AOA in Pearl River Delta of China in response to various habitats, the archaeal amoA genes in soil, marine, river, lake, hot spring and wastewater treatment plant （WWTP） samples were investigated using real-time fluorescent quantitative PCR and clone libraries. Our analyses indicated that the diversity of AOA in various habitats was different and could be clustered into five major clades, i.e., estuary sediment, marine water/sediment, soil, hot spring and Cluster 1. Phylogenetic analyses revealed that the structure of AOA communities in similar ecological habitats exhibited strong relation. The canonical correspondence method indicated that the AOA community structure was strongly correlated to temperature, pH, total organic carbon, total nitrogen and dissolved oxygen variables. Assessing AOA amoA gene copy numbers, ranging from 6.84× 10^6 to 9.45 × 10^7 copies/g in dry soil/sediment, and 6.06× 10^6 to 2.41 ×10^7 copies/L in water samples, were higher than ammonia-oxidizing bacteria （AOB） by 1-2 orders of magnitude. However, AOA amoA copy numbers were much lower than AOB in WWTP activated sludge samples. Overall, these studies suggested that AOA may be a major contributor to ammonia oxidation in natural habitats but play a minor role in highly aerated activated sludge. The result also showed the ratio of AOA to AOB amoA gene abundance was positively correlated with temperature and less correlated with other environmental parameters. New data from our study provide increasing evidence for the relative abundance and diversity of ammonia-oxidizing archaea in the global nitrogen cycle.

稻菜轮作下不同施氮处理对土壤微生物多样性的影响

【目的】分析稻菜轮作模式下不同施氮处理对土壤微生物多样性的影响,为氮肥减量施用提供理论支撑。【方法】设置氮肥全量施用(T1)、氮肥减施(T2)、氮肥配施有机肥(T3)、不施氮肥(CK)4个处理,利用高通量测序技术和生物信息学手段,研究其对土壤真菌和细菌群落结构和多样性的影响。【结果】土壤细菌和真菌群落Alpha多样性分析表明,T1处理的细菌群落Chao1指数和Observed指数低于CK处理,T2、T3处理高于CK,但处理间差异不显著;T1、T2、T3处理的细菌Shannon指数和Simpson指数均高于CK处理,差异不显著。T1、T2、T3处理的真菌Chao1指数和Observed指数均高于CK处理,而Shannon指数和Simpson指数均低于CK处理,差异不显著。微生物群落Beta多样性分析表明4个处理的土壤细菌群落组成基本相似,处理间差异不显著;T3处理的真菌群落组成与CK、T1、T2处理有一定的差异。土壤细菌群落组成基本相似,4个处理的细菌优势菌群均为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、绿弯菌门(Chloronexi)和酸杆菌门(Acidobacteria),T2处理的绿弯菌门相对丰度最高,T3处理的变形菌门相对丰度最高,施氮处理均降低了酸杆菌门、放线菌门和硝化螺旋菌门相对丰度。真菌群落组成有一定的差异性,真菌优势菌群均为子囊菌门(Ascomycota)、被孢霉门(Mortierellomycota)和担子菌门(Basidiomycota),T1处理增加担子菌门的相对丰度,T2处理增加被孢霉门的相对丰度,T3处理子囊菌门相对丰度最高。T2处理显著降低了大理石雕菌属(Marmoricola)相对丰度,T3处理显著增加腐质霉属(Humicola)和青霉菌属(Penicillium)相对丰度,施氮处理均显著降低链格孢属(Alternaria)相对丰度。【结论】在水稻-茎瘤芥轮作模式下,与氮肥全量施用相比,减氮施肥和氮肥配施有机肥均提高了土壤细菌群落的丰富度,降低了真菌群落的丰富度。处理间土壤微生物的群落结构差异不明显,其微生物群落多样性的差异主要体现在大理石雕菌属、腐质霉属、青霉菌属和链格孢属相对丰度的显著变化。

亚急性瘤胃酸中毒湖羊瘤胃液中菌群和B族维生素丰度变化的关联分析

【目的】本试验旨在探讨湖羊亚急性瘤胃酸中毒(subacute rumen acidosis,SARA)对瘤胃液中微生物菌群结构和B族维生素表达丰度的影响,同时分析二者之间的相关性。【方法】选用体况良好的湖羊12只,随机均分为2组,每组6只,对照组饲料精粗比为3∶7,SARA组饲料精粗比为7∶3建立SARA模型。通过16S rRNA测序技术分析菌群结构变化,利用液相色谱-串联质谱(LC-MS)方法分析瘤胃液中B族维生素的表达丰度,并用Pearson法分析二者相关性。【结果】对照组湖羊瘤胃菌群多样性指数(Shannon和Chao1)显著高于SARA组,菌群多样性显著高于SARA组(P<0.05)。在细菌门水平,对照组放线菌门(Actinobacteria)、Candidatus_Saccharibacteria、软壁菌门(Tenericutes)丰度显著高于SARA组(P<0.05);在细菌属水平,对照组双歧杆菌属(Bifidobacterium)、夏普氏菌属(Sharpea)、产丁酸盐菌属(Saccharibacteria)、未分类的瘤胃球菌属(unclassified_Ruminococcaceae)显著高于SARA组(P<0.05);而未分类的脱硫弧菌属(unclassified_Desulfovibrionaceae)、未分类的梭菌属(unclassified_Clostridiales)和拟普雷沃氏菌属(Alloprevotella)显著低于SARA组(P<0.05)。对照组与SARA组筛选出VB 6(吡哆醛、吡哆醇、吡哆胺)、VB 3、VB 9及VB 126种差异代谢物,其表达丰度SARA组显著高于对照组(P<0.05)。Pearson相关性结果显示,6种差异B族维生素与绝大多数瘤胃微生物具有显著相关性(R>0或R<0)。【结论】SARA改变了瘤胃液中菌群门与属水平结构,导致菌群多样性降低,增加了VB 6、VB 3、VB 9及VB 12表达丰度,且与瘤胃液中大部分菌群具有显著相关性。

微粒聚谷氨酸配施化肥对棉花生长和土壤养分及微生物群落结构的影响

利用棉花盆栽试验,设置5个处理(P1(4.5 g微粒聚谷氨酸(γ-PGA)配施1 g化肥)、P2(3 g微粒γ-PGA配施1 g化肥)、P3(1.5 g微粒γ-PGA配施1 g化肥)、N(1 g化肥)和CK(不施肥)),通过分析棉花的农艺性状,并结合高通量测序技术,探究施用微粒γ-PGA配施化肥对棉花植株生长和土壤微生物群落结构的影响,以确定合理的配施剂量。结果表明,微粒γ-PGA配施化肥的棉花农艺性状优于单施化肥和不施肥,1.5 g微粒γ-PGA配施化肥效果最佳。在棉花生育期微粒γ-PGA配施化肥的土壤中全钾、铵态氮和有效磷的含量高于单施化肥和不施肥,在采后土壤中全钾、铵态氮、有效磷和有效钾含量保持较高水平。高通量测序结果表明,微粒γ-PGA配施化肥会引起微生物的丰富度和多样性的降低,但可以改善微生物群落结构,在采摘之后,土壤中的变形菌门、子囊菌门和被孢霉门的相对丰度都呈降低态势,而放线菌门、酸杆菌门和担子菌门的相对丰度则呈上升态势,与单施化肥和不施肥相比,大部分菌门依旧保持高的相对丰度。冗余(RDA)分析可知,土壤微生物优势菌门受包括全磷、全钾、有效磷、有效钾、酸碱度、有机质含量等多个关键因子的影响,随着时间的变化,微生物优势菌门受这些关键因子的影响也可能会有差异。微粒γ-PGA配施化肥可促进棉花的生长发育,虽会降低细菌和真菌群落的整体丰富度与多样性,但使微生物群落种类相对集中在部分有益菌群上,且在棉花采摘后依旧能维持较高的相对丰度,可改善土壤质量,维持较高的土壤生物活性,有利于农业生产。

长江口水体化能自养固碳过程的潮周期变化特征及影响因素

河口水体中硝化微生物的化能自养固碳(DCF)对碳氮循环过程有着重要影响,但目前关于河口水体氨氧化微生物对DCF过程的贡献鲜见报道。以长江口为研究区,利用14C和15N同位素示踪技术,分别测定了大潮和小潮期间水体DCF和硝化速率,并通过实时荧光定量PCR技术量化了相关功能基因丰度。结果表明,长江口水体大小潮期间,DCF和硝化速率分别介于170.72-1007.35nmol·L^(-1)·d^(-1)和1.45-70.75 nmol·L^(-1)·h^(-1),呈现大潮速率相对较高,小潮速率低的变化特征,且底层水体DCF和硝化速率显著高于表层水体。水体中铵盐和可溶性无机碳浓度是影响DCF和硝化速率的关键环境因子。定量PCR结果表明,大潮和小潮时cbbL基因丰度分别为0.40×10^(8)-3.40×10^(8)copies·L^(-1)和0.49×10^(8)-2.27×10^(8)copies·L^(-1),均高于cbbM基因丰度(大潮:0.67×10^(8)-9.84×10^(6) copies·L^(-1),小潮:0.75×10^(8)-5.73×10^(6) copies·L^(-1))。小潮时水体accA基因丰度(0.16×10^(8)-2.65×10^(8) copies·L^(-1))高于大潮时(0.20×10^(8)-3.92×10^(8) copies·L^(-1)),并且底层均高于表层。在整个潮周期中,自养固碳功能基因丰度总体呈现涨潮时增加,落潮时降低的变化趋势。氨氧化古菌(AOA)和氨氧化细菌(AOB)是DCF过程的主要贡献者,AOAamoA和AOBamoA丰度在大潮和小潮之间存在显著差异,大潮时AOAamoA基因丰度(0.22×10^(7)-3.59×10^(7) copies·L^(-1))明显高于AOB amoA基因丰度(0.26×10^(7)-1.61×10^(7) copies·L^(-1)),而小潮时AOB amoA丰度占据优势,为0.92×10^(6)-1.32×10^(6) copies·L^(-1),表明潮汐过程可通过改变水体化能自养微生物群落组成来影响DCF。该研究深化了长江口潮周期水体DCF和硝化过程速率变化特征的认识,揭示了河口水体硝化微生物驱动的DCF过程的重要性,以期为全球变化背景下河口生态系统碳汇功能评估提供一定的科学参考。

成龄胶园间作砂仁对根际和非根际土壤微生物数量的影响

为探究橡胶林下间作砂仁对根际及非根际土壤微生物数量丰度的影响,以橡胶树单作、砂仁单作和橡胶树/砂仁间作的根际和非根际土壤作为试验材料,测定了不同处理后非根际土壤和根际土壤中细菌、真菌、放线菌的数量。结果表明:橡胶树/砂仁间作能显著提高砂仁根际土壤中细菌、真菌和放线菌的数量;与砂仁相比,间作后橡胶树根际土壤中细菌和放线菌数量增加极显著(P<0.01),真菌数量较橡胶树单作差异不显著(P>0.05)。在非根际土壤中,间作模式下土壤中的细菌、真菌、放线菌数量分别达到11.46×10^(8)CFU/g、8.22×10^(5)CFU/g和3.32×10^(4)CFU/g,均显著高于橡胶树单作和砂仁单作。不同处理下3种土壤微生物类群的数量变化都呈现同一种趋势,即橡胶树/砂仁间作>橡胶树单作,橡胶树/砂仁间作>砂仁单作。由此可见,在成龄胶园间作砂仁能够有效提高砂仁根际土壤中和非根际土壤中的微生物数量丰度,改善其微生态环境,这一结果为揭示橡胶树间作砂仁模式下的土壤微生物生态学研究奠定了理论基础。

Nitrogen transformation processes in soil along a High Arctic tundra transect

Soil nitrogen(N)transformation processes in the High Arctic tundra are poorly understood even though nitrogen is one of the main limiting nutrients.We analyzed soil samples collected along a High Arctic tundra transect to investigate spatial variability in key nitrogen transformation processes,functional gene abundances,ammonia-oxidizing archaea(AOA)community structures,and key nitrogen transformation regulators.The potential denitrification rates were higher than the nitrification rates in the soil samples,although nitrification may still regulate N2O emissions from tundra soil.The nutrient(total carbon,total organic carbon,total nitrogen,and NH_(4)^(+)-N)contents were important determinants of spatial variability in the potential denitrification rates of soil along the tundra transect.The total sulfurcontent was the main variable controlling potential nitrification processes,probably in association with sulfate-reducing bacteria.The nitrate content was the main variable affecting potential dissimilatory nitrate reduction to ammonium.AOA and ammonia-oxidizing bacteria amoA,nirS,and anammox 16S rRNA genes were found in all of the soil samples.AOA play more important roles than ammonia-oxidizing bacteria in soilnitrification.Anammox bacteria may utilize NO_(2)^(-)produced through nitrification.Phylogenetic analysis indicated that the AOA amoA sequences could be grouped into eight unique operational taxonomic units(OTUs)with a 97%sequence similarity and were affiliated with three group 1.1b Nitrososphaeraclusters.The results indicated that heterogeneous environmental factors(e.g.,the carbon and nitrogen contents of soil)along the High Arctic tundra transect strongly affected the nitrogen transformation rate and relevant functional gene abundances in soil.

白洋淀湖滨湿地岸边带氨氧化古菌与氨氧化细菌的分布特性

通过分子生物学分析方法,以amoA基因为标记,考察了氨氧化古菌(Ammonia-Oxidizing Archaea,AOA)和氨氧化细菌(Ammonia-Oxidizing Bacteria,AOB)在华北平原的白洋淀这一典型湖泊的湖滨湿地岸边带系统中的生物多样性和丰度分布。在前人的研究中,氨氧化古菌在海洋、原生态土壤和人为干扰土壤等环境中主导氨氧化过程的完成。但本研究发现,在湿地岸边带系统中氨氧化过程并不是完全由氨氧化古菌主导完成,即氨氧化古菌和氨氧化细菌在不同区域分别占据主导地位。根据主导微生物的不同,可以将湿地岸边带区域划分为陆相区、中间区和湖相区。在湿地岸边带陆相区,氨氧化古菌主导氨氧化过程,氨氧化古菌的amoA基因丰度是氨氧化细菌的526倍(AOA:1.23×108个/g干土;AOB:2.34×105个/g干土);在岸边带湖相区,氨氧化细菌主导氨氧化过程,氨氧化古菌的amoA基因丰度只有氨氧化细菌的1/50倍(AOA:3.17×106个/g干土;AOB:1.39×108个/g干土);在岸边带中间区,两种微生物对氨氧化过程的贡献相当,二者的amoA基因丰度也相当(AOA:9.83×106,AOB:4.08×106)。研究还发现,湿地中间区的微生物生物多样性高于陆相区和湖相区。在湿地中间区,氨氧化古菌和氨氧化细菌的生物多样性都最高,分别有5和7个操作分类单元(OTUs);相比之下,岸边带陆相区和湖相区的多样性依次降低,陆相区的氨氧化古菌和氨氧化细菌分别有3和6个操作分类单元,湖相区的氨氧化古菌和氨氧化细菌分别有2和6个分类单元。所得结论反映了湿地岸边带极强的空间异质性。

黄土高原旱作区马铃薯连作根际土壤微生物群落变化特征

本文探讨了土壤微生物对马铃薯连作的响应,旨在揭示连作土壤退化的微生物特征。采用盆栽试验和MiSeq高通量测序技术相结合的方法,以休耕(CK)和轮作(R_rh)为对照,研究了马铃薯连作1年(1_rh)、3年(3_rh)和5年(5_rh)根际土壤微生物群落特征。结果表明,与CK和轮作相比,3_rh和5_rh土壤样品Ace指数、Chao指数、Shannon指数显著降低。与轮作相比,马铃薯连作土壤细菌中变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和酸杆菌门(Acidobacteria)相对丰度较高,土壤真菌中子囊菌门(Ascomycota)相对丰度较低。细菌群落中,较轮作,1_rh、3_rh、5_rh气微菌属(Aeromicrobium)的数量分别增加258.01%、625.93%、76.04%,节杆菌属(Arthrobacter)分别增加245.42%、1258.12%、58.89%,链霉菌属(Streptomyces)分别增加203.83%、116.74%、311.61%。真菌群落中,较轮作,3_rh镰孢属(Fusarium)数量增加了225.00%,5_rh毛壳属(Chaetomium)数量降低了31.58%,1_rh、3_rh、5_rh久浩酵母属(Guehomyces)的数量分别降低55.40%,58.14%,78.37%;壶菌属(Spizellomyces)在休耕和轮作土壤中数量较多,而在连作3年和5年土壤中数量很少,接近检测底限。说明马铃薯长期连作降低了土壤微生物多样性,微生物优势种群发生改变,土壤微生物群落结构失衡。

玉米秸秆对土壤微生物性质的影响

以黑钙土为供试土壤,初步研究了玉米秸秆对黑钙土微生物数量及种群丰富度、种群更替的影响。180 d的培养试验结果表明:玉米秸秆对土壤微生物的数量、活性具有促进作用。其中,玉米秸秆对土壤真菌数量的影响大于对细菌数量的影响,细菌与真菌的数量比(B/F)由1.42降低到1.25。微生物种群丰富度下降,具有使土壤微生物区系由细菌型向真菌型转化的趋势。

长期施肥对棕壤氨氧化细菌和古菌丰度的影响

【目的】氨氧化是氮转化过程的限速步骤,其由氨氧化微生物所驱动。本研究旨在探明37年玉米–大豆轮作施肥条件下影响棕壤氨氧化微生物丰度的主要影响因子及变化规律。【方法】以沈阳农业大学棕壤肥料长期定位试验耕层土壤(0—20 cm)为材料,选取其中9个施肥处理进行取样分析:不施肥(CK)、低量氮肥(N_1)、高量氮肥(N_2)、氮磷肥(N_1P)、氮磷钾肥(N1PK)、高量有机肥(M_2)、高量有机肥+低量氮肥(M_2N_1)、高量有机肥+氮磷肥(M_2N_1P)、高量有机肥+氮磷钾肥(M_2N_1PK)。采用实时荧光定量PCR技术测定其氨氧化微生物丰度,通过对土壤基本化学性质和氨氧化微生物丰度的冗余分析找出影响氨氧化微生物丰度的主要因素。【结果】施用有机肥处理的土壤p H、有机质、全氮、碱解氮、速效钾、速效磷、铵态氮、硝态氮含量明显高于不施肥和单施化肥处理。各施肥处理土壤有机质、全氮、碱解氮、速效钾、速效磷的含量总体呈现有机肥处理>化肥处理>CK;与不施肥处理(CK)相比,单施化肥处理显著降低了土壤p H值,施用有机肥处理显著提高了土壤pH值,其中N_2处理的土壤pH最低,M_2处理的土壤pH最高。不同施肥处理氨氧化细菌(AOB)的丰度为0.94×10~6~5.77×10~6 copies/g干土,氨氧化古菌(AOA)的丰度为3.56×10~6~1.22×10~7 copies/g干土;施用有机肥处理AOB和AOA丰度显著高于不施肥和单施化肥处理,其中M2处理的AOB和AOA丰度最高,单施氮肥处理的AOB和AOA丰度最低。冗余分析(RDA)表明,影响棕壤AOB和AOA丰度的主要环境因子有土壤pH、有机质、全氮、碱解氮、速效磷、速效钾,且与AOB和AOA丰度呈正相关关系。【结论】长期轮作施肥显著改变了棕壤的化学性质,从而对氨氧化微生物的丰度产生了显著影响。长期施用有机肥显著提高了土壤养分含量及AOB和AOA的丰度,对维持土壤氨氧化微生物的数量起到十分重要的作用;同时试验结果也为今后通过改变土壤p H、有机质、全氮、碱解氮、速效磷、速效钾等性质对AOB和AOA进行调节提供了依据。

白令海表层沉积物中硅质生物的变化及其环境控制因素

中国首次北极科学考察在白令海采取了 12个表层沉积物样品 ,其中对硅质生物和陆源碎屑的详细研究发现 ,它们主要由硅藻、放射虫和海绵骨针组成 .其中 ,硅藻在样品中的丰度均占绝对优势 ,高出放射虫和海绵骨针一个数量级 .它们与环境控制因素关系的分析表明 ,硅藻、放射虫和海绵骨针丰度的高低及其保存程度与深度、温度、盐度和受大规模季节性气候变化控制的表层海水的高营养和高生产力 ,以及陆源物质输入的变化密切相关 .