缢蛏养殖池塘氨氧化微生物的季节变化特征

为探究缢蛏(Sinonovacula constricta)养殖池塘中氨氧化细菌(AOB)和氨氧化古菌(AOA)的季节变化及其环境因子相关性, 试验以amoA基因为分子标记, 利用荧光定量PCR技术对养殖池塘水体及沉积物中的AOA和AOB进行了研究。结果显示, 季节变化对于水体及沉积物中的AOA和AOB的amoA基因丰度有一定的影响, 不同季节的水体及沉积物中AOA含量均比AOB含量高一个数量级。其中水体中AOB在秋季显著高于其余三季(P<0.05); AOA在冬季最低, 且显著低于春秋两季(P<0.05)。沉积物中AOB和AOA均在冬季显著高于其余三季(P<0.05)。环境因子相关性分析结果表明: 水体中AOB丰度与氨氮成显著正相关(P<0.05), 与亚硝氮成显著负相关(P<0.05); AOA丰度与水温成正显著相关(P<0.05), 与硝氮成负显著相关(P<0.05)。沉积物中AOB丰度与溶解氧、硝氮、总氮及亚硝氮成显著正相关(P<0.05), 与水温成显著负相关(P<0.05); AOA丰度与溶解氧、总氮、硝氮成显著性正相关(P<0.05), 与水温成负显著相关(P<0.05)。多元线性回归方程结果显示, 缢蛏养殖池塘的AOA及AOB丰度与硝氮密切相关。研究表明, AOA在缢蛏养殖池塘氨氧化进程中占据主导地位, AOA和AOB丰度受盐度、温度、氮素浓度及溶解氧等环境因子的共同影响。     

小兴安岭酸性泥炭土硝化作用的类型及其驱动因子

以小兴安岭酸性森林泥炭土为研究对象,通过加入10 mL·L^-1乙炔及不同浓度的外源硫酸铵(0、1.2、6.0 mmol N·kg^-1)进行硝化培养试验,探究酸性泥炭土中硝化作用类型及主要驱动因子.结果表明:无论有无外加氮源,酸性泥炭土均存在较强的矿化作用(0.9～1.4 mg N·kg^-1·d^-1),经过2周的培养均发生了硝化作用(0.4～0.6 mg N·kg^-1·d^-1),且不同浓度硫酸铵处理之间无显著差异;而乙炔处理虽有较强的矿化作用(0.8 mg N·kg^-1·d^-1),但未发生明显的硝化作用(0 mg N·kg^-1·d^-1),说明该酸性泥炭土以自养硝化为主,外源无机氮源浓度对硝化作用无显著影响,硝化底物NH₃的主要来源不是外源硫酸铵,更可能来源于土壤中有机氮的矿化.培养0～14 d,无论有无外加氮源,酸性泥炭土氨氧化细菌(AOB)和古菌(AOA)丰度均显著增加,但不同浓度硫酸铵处理间无显著差异,表明外源无机氮浓度对氨氧化微生物的生长无显著促进作用.与不加乙炔的对照相比,乙炔处理AOB和AOA丰度随时间均无显著变化,推测AOA与AOB在该酸性泥炭土的硝化过程中都可能起一定的作用.     

秸秆还田对玉米根际氨氧化微生物群落及红壤硝化潜势的影响

为探讨酸性红壤根际氨氧化微生物群落以及硝化作用对不同秸秆还田处理的响应,基于中国科学院鹰潭红壤生态实验站设置的秸秆还田长期试验平台(9年),采用荧光定量PCR和高通量测序技术,研究不同秸秆还田处理(不施肥(CK);氮磷钾肥(NPK);氮磷钾肥+秸秆(NPKS);氮磷钾肥+秸秆猪粪配施(NPKSM);氮磷钾肥+秸秆生物炭(NPKB))下玉米根际土壤氨氧化古菌(ammonia-oxidizing archaea, AOA)和细菌(ammonia-oxidizing bacteria, AOB)丰度和群落结构的变化,揭示了秸秆还田对根际氨氧化微生物群落结构和硝化潜势(potential nitrification activity, PNA)的影响机制。结果发现：相比CK和NPK处理,秸秆还田显著提高了土壤养分含量和硝化潜势,其中有机碳(SOC)、全氮(TN)、全磷(TP)、速效磷(AP)、速效钾(AK)、硝态氮(NO~-₃-N)和铵态氮(NH~+₄-N)含量显著增加,NPKSM处理对土壤肥力提升效果最佳。AOA的硝化潜势显著高于AOB,表明AOA...     

不同利用方式对红壤坡地微生物多样性和硝化势的影响

采集了中国科学院桃源农业生态试验站红壤坡地农田、自然恢复林和茶园土壤样品,采用末端限制性酶切片段长度多态性分析(T.RFLP)技术分析土壤细菌、古菌、氨氧化细菌(AOB)和氨氧化古菌(AOA)的多样性,采用好气培养法测定不同土壤的硝化势,研究不同土地利用方式对微生物多样性和硝化势的影响.结果表明:土壤AOB和AOA多样性指数差异不显著,且在3种不同土地利用方式中呈现相同的趋势,均为农田=茶园>自然恢复林;通过RDA分析发现,不同利用方式造成土壤理化性状的改变是影响土壤AOA和AOB群落结构的主要原因;好气培养法测得不同土壤硝化势农田最高,茶园次之而自然恢复林最低;相关性分析显示,硝化势与细菌16S rRNA、AOA和AOB amoA基因多样性指数呈显著正相关,其中与AOA amoA基因关系最为密切;总体来说,红壤坡地不同利用方式改变了土壤细菌、古菌、AOA和AOB的多样性,土壤AOB和AOA积极参与了土壤的硝化过程,且AOA在氨氧化微生物群落生态功能中占有重要地位,AOA比AOB与硝化势的关系更为密切.     

东湖表层沉积物中氨氧化古菌和氨氧化细菌丰度及多样性研究

研究通过高通量测序和荧光定量PCR等分子生物学分析方法, 以氨单加氧酶基因(amoA)为分子标记, 研究了东湖表层沉积物中AOA和AOB的群落多样性、丰度及其与环境因子的关系。结果表明, 东湖沉积物AOA主要为Nitrosopumilus, 其群落结构与沉积物中总氮含量显著相关, 而AOB主要为Nitrosomonas, 群落结构与沉积物中总有机碳和总磷显著相关。此外, 不同季节AOA丰度均高于AOB, 且沉积物AOA数量与温度呈显著负相关, 但AOB丰度变化不明显。东湖沉积物中AOA可能主导了氨氧化过程。     

不同林龄杉木人工林土壤硝化和反硝化作用

对不同林龄杉木人工林(5、8、21、27和40年生)土壤硝化与反硝化过程及功能微生物丰度进行研究。结果表明: 土壤净硝化速率随林龄的增加波动变化,8、27年生杉木人工林土壤净硝化速率显著低于5、21和40年生。27年生杉木人工林土壤氨氧化古菌(AOA) amoA基因丰度显著低于40年生,其他林龄AOA amoA基因丰度之间无显著差异。不同林龄杉木人工林的氨氧化细菌(AOB) amoA基因丰度、反硝化功能基因丰度以及反硝化潜势均无显著差异。逐步回归分析表明,土壤氨氧化微生物AOA amoA基因丰度受土壤理化性质的影响不显著,土壤总碳和土壤pH是影响AOB丰度的重要因子。反硝化功能基因narG、nirK及nosZ随土壤pH的增加而增加,编码亚硝酸盐还原酶(NIR)的功能基因(nirK、nirS)受土壤总碳的影响。林龄可通过影响AOA amoA基因丰度影响土壤净硝化速率。林龄直接作用于反硝化潜势,或间接影响土壤微生物生物量碳、土壤pH及反硝化功能基因丰度(narG和nirK),进而影响反硝化潜势。相较于反硝化过程,土壤硝化作用及AOA amoA基因丰度对杉木林分发育更加敏感,可适当延长轮伐期以降低土壤硝化作用造成的氮流失风险。     

宏基因组技术研究泥岩母质发育的三种不同pH紫色土硝化微生物群落演变规律

【目的】揭示典型农田旱地紫色土硝化微生物的群落组成及其对pH的响应规律。【方法】针对同一母质发育但pH差异显著的3种紫色土,利用宏基因组技术深度测序研究土壤中硝化微生物丰度和群落,包括氨氧化古菌(ammonia-oxidizing archaea,AOA),氨氧化细菌(ammonia-oxidizing bacteria,AOB),亚硝酸盐氧化细菌(nitrite-oxidizingbacteria,NOB)和全程氨氧化细菌(completeammoniaoxidizer,Comammox)。【结果】土壤中硝化微生物的丰度占总微生物的2.130%–6.082%。3种紫色土中AOA、AOB和NOB的相对丰度有显著差异:酸性紫色土中AOA的相对丰度显著大于碱性紫色土,而AOB则相反;NOB的相对丰度在中性紫色土中最高。所有土样中均发现了1种全程氨氧化细菌Candidatus Nitrospira inopinata (Ca. N. inopinata),其在中性紫色土中相对丰度最高,占总微生物的0.203%。3种不同pH紫色土中AOA均以Nitrososphaera为主,NOB均以Nitrospira为主;酸性紫色土中AOB以Nitroscoccus为主,而中性和石灰性紫色土中则以Nitrosospira为主。Pearson相关性分析发现,土壤pH和铵态氮是影响硝化微生物丰度最大的两个因子。【结论】Comammox存在于3种不同pH紫色土中,且偏好中性环境;AOA、AOB和NOB群落结构和相对丰度都存在显著差异,结合相关性分析发现土壤pH和铵态氮是导致差异最重要的两个因子。     

水分管理模式对水稻吸收累积镉的影响及其作用机理

利用盆栽试验研究了不同水分管理模式（全生育期淹水,WF;分蘖期晒田,TP;乳熟期晒田,MP;分蘖-乳熟期两次晒田,TMP;湿润灌溉,WI）对Cd污染红黄泥和潮泥田水稻吸收累积Cd的影响.结果表明：两种土壤Fe²⁺含量均以WF处理最高,TMP处理最低;潮泥田和红黄泥WF处理的Fe²⁺含量分别比TMP增加了585.4%和1316.3%(P<0.01).不同处理的两种土壤有效S和有效态Cd含量顺序均表现为：WF2+和有效S含量变化对两种Cd污染土壤水稻吸收累积Cd产生显著影响,其中有效S的影响程度显著大于Fe²⁺.     

不同施肥制度对石灰性紫色水稻土中氨氧化古菌群落结构的影响

研究不同施肥制度对水稻土氨氧化古菌(AOA)群落结构和垂直分布特征的影响,可以深入认识不同施肥制度下的石灰性紫色水稻土氮素循环特征及微生物驱动机制,为该地区科学施肥、培肥地力提供理论依据。利用化学分析和变性梯度凝胶电泳(DGGE)对不同施肥制度下石灰性紫色水稻土理化性质和AOA群落结构进行了分析。结果显示:相对于无肥处理,施肥会降低石灰性紫色水稻土pH和硝氮含量,而增加土壤有机质、全氮和氨氮含量。伴随土壤深度增加,土壤pH增加,全氮和硝氮含量降低,氨氮含量变化趋势不明显。不同施肥制度在不同土壤深度对石灰性紫色水稻土AOA群落结构产生不同的胁迫效应,不同施肥制度下的AOA群落结构在0—20 cm处差异不明显;土壤深度增加,不同施肥制度下的AOA群落结构表现出明显差异,CK和N肥处理下的AOA群落结构较简单。AOA群落结构多样性指数和丰富度随土壤深度增加而减小。石灰性紫色水稻土AOA与来自不同土壤和水体环境的AOA具有明显相似性。冗余梯度分析(RDA)显示pH(P=0.012)是造成石灰性紫色水稻土AOA群落结构差异的主要原因。研究揭示石灰性紫色水稻土中的AOA群落结构受施肥制度明显影响并表现出明显的垂直分布特征。     

硝化细菌对加州鲈池塘水质影响及底质净化作用

为研究有益菌硝化细菌(Nitrifying bacteria)对加州鲈(Micropterus salmoides)高密度养殖池塘水质及底质的影响,在模拟加州鲈高密度养殖池塘单独施用硝化细菌,通过检测养殖水体pH、氨氮(NH4+-N)、亚硝酸盐氮、总氮(TN)及总磷(TP)等水质指标,底质沉积物中有机物、全氮及全磷等指标以及池塘浮游动植物量,以评价硝化细菌处理对加州鲈高密度养殖水体水质影响及底质净化作用。结果表明,硝化细菌能够稳定养殖水体pH,降低水体亚硝酸盐氮浓度,减缓养殖水体TN浓度上升,去除底质沉积物中有机物及全磷含量,有机物去除率达54.17%,全磷去除率达43.34%。硝化细菌处理前期浮游动植物总量高于对照池塘,后期逐渐减少并趋于稳定。     

Review of ammonia-oxidizing bacteria and archaea in freshwater ponds

Aquaculture ponds are simple and unique ecosystems, which are affected intensively by human activities. In this mini-review, we focus our attention on the distribution and community diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in pond water and sediments, as well as the possible ecological mechanisms involved. Moreover, we discuss the possibility of increasing the activity of ammonia-oxidizing organisms in order to improve the water quality in aquaculture ponds. Compared with eutrophic lakes, the significantly higher ammonia concentration in pond water does not lead to significantly higher AOB levels, and the abundance of AOA is too low to quantify accurately. Similar to eutrophic lakes, high abundances of AOA and AOB are present in the surface sediments at the same time, where the oxidation of ammonia is performed mainly by AOB. AOB and AOA exhibit significant seasonal variations in aquaculture ponds, which are affected by the temperature, pH, and dissolved oxygen. The dominant AOB species are Nitrosomonas and the Nitrosospira lineage in pond environments. Nitrososphaera or members of the Nitrososphaera-like cluster dominate the AOA species in surface sediments, whereas the Nitrosopumilus cluster dominates the deeper sediments. AOB and AOA can be enriched on artificial substrates suspended in the pond water, thereby potentially improving the water quality.

     

Seasonal dynamics of ammonia-oxidizing microorganisms in freshwater aquaculture ponds

An annual investigation into the abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in fresh water aquaculture ponds was performed by quantitative PCR of the amoA gene. The results showed that AOB were the main ammonia-oxidizing microorganisms in water, and significantly higher copy numbers of the AOB amoA gene were observed in the summer (Aug 2012), while no significant differences were detected among the other three seasons. AOA showed low abundances throughout the year. The predominance of AOB in aquaculture water was suggested to be related to photoinhibition. Both the AOB and AOA amoA genes in aquaculture pond sediments showed typical seasonal patterns. The maximum density of AOB was observed in the autumn (Nov 2012) and winter (Jan 2013), while the maximum density of AOA was observed in winter. The minimum densities of both AOA and AOB occurred in the summer. The concentration of the AOA amoA gene was higher than that of the AOB amoA gene in sediments by almost one order of magnitude, which indicates that AOA are the dominant ammonia-oxidizing microorganisms in the aquaculture pond sediments. Dissolved oxygen is suggested to be the key factor determining the predominance of AOA in pond sediments.     

Fish growth enhances microbial sulfur cycling in aquaculture pond sediments

Microbial sulfate reduction and sulfur oxidation are vital processes to enhance organic matter degradation in sediments. However, the diversity and composition of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) and their environmental driving factors are still poorly understood in aquaculture ponds, which received mounting of organic matter. In this study, bacterial communities, SRB and SOB from sediments of aquaculture ponds with different sizes of grass carp (Ctenopharyngodon idellus) were analysed using high-throughput sequencing and quantitative real-time PCR (qPCR). The results indicated that microbial communities in aquaculture pond sediments of large juvenile fish showed the highest richness and abundance of SRB and SOB, potentially further enhancing microbial sulfur cycling. Specifically, SRB were dominated by Desulfobulbus and Desulfovibrio, whereas SOB were dominated by Dechloromonas and Leptothrix. Although large juvenile fish ponds had relatively lower concentrations of sulfur compounds (i.e. total sulfur, acid-volatile sulfide and elemental sulfur) than those of larval fish ponds, more abundant SRB and SOB were found in the large juvenile fish ponds. Further redundancy analysis (RDA) and linear regression indicated that sulfur compounds and sediment suspension are the major environmental factors shaping the abundance and community structure of SRB and SOB in aquaculture pond sediments. Findings of this study expand our current understanding of microbial driving sulfur cycling in aquaculture ecosystems and also provide novel insights for ecological and green aquaculture managements.     

Distribution patterns of ammonia-oxidizing archaea and bacteria in sediments of the eastern China marginal seas

Ammonia-oxidizing archaea (AOA) and bacteria (AOB) vary in their contribution to nitrification in different environments. The eastern China marginal seas (ECMS) are featured by complex river runoffs and ocean currents, forming different sediment patches. Here, via quantitative PCR and clone library analysis of the amoA genes, we showed that AOB were more abundant than AOA in ECMS sediments. The abundance, diversity and richness of AOA, but not AOB, were higher in the East China Sea (ECS) than in the Yellow Sea (YS) and Bohai Sea (BS). Nitrosopumilus (AOA) and Nitrosospira (AOB) were predominant lineages, but their abundances varied significantly between ECS, and BS and YS. This was mainly attributed to salinity and dissolved oxygen of the bottom water. The discovery of a high abundance of Nitrosophaera at estuarine sites suggested strong terrigenous influence exerted on the AOA community. In contrast, variations in ocean conditions played more important roles in structuring the AOB community, which was separated by bottom water dissolved oxygen into two groups: the south YS, and the north YS and BS. This study provides a comprehensive insight into the spatial distribution pattern of ammonia-oxidizing prokaryotes in ECMS sediments, laying a foundation for understanding their relative roles in nitrification.     

稻作系统对淡水养殖池塘富营养化的修复效应及应用前景

养殖池塘富营养化是目前制约我国淡水养殖业可持续发展的关键因素。稻作系统具有显著的净化水质能力,如何将稻作系统和淡水养殖系统进行生态耦合实现氮、磷养分的循环利用,是淡水养殖池塘富营养化生态修复的一个重要研究方向。通过文献调研和实地考察,综合分析了浮床种稻-原位修复、稻田湿地-异位修复、稻鱼生态种养3种耦合方式对养殖池塘富营养化的修复效应,以及氮、磷养分综合利用效率,归纳总结了不同模式的技术特点以及应用中存在的问题,并就修复技术研究和生态补偿提出了培育生态修复专用水稻品种,加强稻作系统生态修复理论研究和技术推广,建立养殖池塘富营养化修复的生态补偿机制等建议。     

硫酸盐对淡水养殖池塘表层底泥微生物的影响

硫酸盐引起的生态学效应已得到了越来越多的关注,但目前关于硫酸盐对养殖池塘底泥微生物的影响还知之甚少。【目的】探究不同浓度硫酸盐对养殖池塘底泥微生物的影响规律及可能的机制。【方法】本研究利用采集自养殖池塘的底泥和表层水构建了试验系统,研究了加入约0 mg/L （对照组）、30 mg/L （T1处理组）、150 mg/L （T2处理组）、500 mg/L （T3处理组） Na₂SO₄后表层底泥微生物的丰度、多样性、组成和共生网络的变化规律,并分析了环境影响因素。【结果】孵育第30天前,各实验组底泥微生物变化不大;但到第50天时,T2和T3处理组微生物丰度和多样性相比对照组均明显下降。相比其他实验组,T1处理组酸杆菌门（Acidobacteriota）、拟杆菌门（Bacteroidota）相对丰度出现显著升高（P<0.05）,T3处理组变形菌门（Proteobacteria）和放线菌门（Actinobacteriota）相对丰度出现显著升高（P<0.05）。与对照组相比,T1处理组增加了较多差异类群（62种）,而T3处理组差异类群大量减少（45种）。共生网络图分析显示硫酸盐浓度的增加引起了底泥微生物网络复杂性的增加,说明微生物群落可能通过自身的调节来响应硫酸盐引起的环境改变。冗余分析（redundant analysis,RDA）和相关性分析揭示底泥总有机碳、总氮和氧化还原电位是影响底泥微生物的主要环境因素,提示底泥微生物可能受到硫酸盐和有机质作用的影响。【结论】较长时间的高浓度硫酸盐会对池塘底泥微生物群落造成重要影响,微生物群落自身的转变和硫酸盐引起的有机质分解改变可能是造成微生物群落变化的关键因素。     

Niche Differentiation of Ammonia-Oxidising Archaea (AOA) and Bacteria (AOB) in Response to Paper and Pulp Mill Effluent

Sediment organic loading has been shown to affect estuarine nitrification and denitrification, resulting in changes to sediment biogeochemistry and nutrient fluxes detrimental to estuarine health. This study examined the effects of organic loading on nutrient fluxes and microbial communities in sediments receiving effluent from a paper and pulp mill (PPM) by applying microcosm studies and molecular microbial ecology techniques. Three sites near the PPM outfall were compared to three control sites, one upstream and two downstream of the outfall. The control sites showed coupled nitrification–denitrification with minimal ammonia release from the sediment. In contrast, the impacted sites were characterised by nitrate uptake and substantial ammonia efflux from the sediments, consistent with a decoupling of nitrification and denitrification. Analysis of gene diversity demonstrated that the composition of nitrifier communities was not significantly different at the impacted sites compared to the control sites; however, analysis of gene abundance indicated that whilst there was no difference in total bacteria, total archaea or ammonia-oxidising archaea (AOA) abundance between the control and impacted sites, there was a significant reduction in ammonia-oxidising bacteria (AOB) at the impacted sites. The results of this study demonstrate an effect of organic loading on estuarine sediment biogeochemistry and highlight an apparent niche differentiation between AOA and AOB.     

Quantitative analyses of the abundance and composition of ammonia-oxidizing bacteria and ammonia-oxidizing archaea of a Chinese upland red soil under long-term fertilization practices

The abundance and composition of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated by using quantitative real-time polymerase chain reaction, cloning and sequencing approaches based on amoA genes. The soil, classified as agri-udic ferrosols with pH (H(2)O) ranging from 3.7 to 6.0, was sampled in summer and winter from long-term field experimental plots which had received 16 years continuous fertilization treatments, including fallow (CK0), control without fertilizers (CK) and those with combinations of fertilizer nitrogen (N), phosphorus (P) and potassium (K): N, NP, NK, PK, NPK and NPK plus organic manure (OM). Population sizes of AOB and AOA changed greatly in response to the different fertilization treatments. The NPK + OM treatment had the highest copy numbers of AOB and AOA amoA genes among the treatments that received mineral fertilizers, whereas the lowest copy numbers were recorded in the N treatment. Ammonia-oxidizing archaea were more abundant than AOB in all the corresponding treatments, with AOA to AOB ratios ranging from 1.02 to 12.36. Significant positive correlations were observed among the population sizes of AOB and AOA, soil pH and potential nitrification rates, indicating that both AOB and AOA played an important role in ammonia oxidation in the soil. Phylogenetic analyses of the amoA gene fragments showed that all AOB sequences from different treatments were affiliated with Nitrosospira or Nitrosospira-like species and grouped into cluster 3, and little difference in AOB community composition was recorded among different treatments. All AOA sequences fell within cluster S (soil origin) and cluster M (marine and sediment origin). Cluster M dominated exclusively in the N, NP, NK and PK treatments, indicating a pronounced difference in the community composition of AOA in response to the long-term fertilization treatments. These findings could be fundamental to improve our understanding of the importance of both AOB and AOA in the cycling of nitrogen and other nutrients in terrestrial ecosystems.     

Spatial variability in nitrification rates and ammonia-oxidizing microbial communities in the agriculturally impacted Elkhorn Slough estuary, California

Ammonia oxidation-the microbial oxidation of ammonia to nitrite and the first step in nitrification-plays a central role in nitrogen cycling in coastal and estuarine systems. Nevertheless, questions remain regarding the connection between this biogeochemical process and the diversity and abundance of the mediating microbial community. In this study, we measured nutrient fluxes and rates of sediment nitrification in conjunction with the diversity and abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing betaproteobacteria (β-AOB). Sediments were examined from four sites in Elkhorn Slough, a small agriculturally impacted coastal California estuary that opens into Monterey Bay. Using an intact sediment core flowthrough incubation system, we observed significant correlations among NO(3)(-), NO(2)(-), NH(4)(+), and PO(4)(3+) fluxes, indicating a tight coupling of sediment biogeochemical processes. (15)N-based measurements of nitrification rates revealed higher rates at the less impacted, lower-nutrient sites than at the more heavily impacted, nutrient-rich sites. Quantitative PCR analyses revealed that β-AOB amoA (encoding ammonia monooxygenase subunit A) gene copies outnumbered AOA amoA gene copies by factors ranging from 2- to 236-fold across the four sites. Sites with high nitrification rates primarily contained marine/estuarine Nitrosospira-like bacterial amoA sequences and phylogenetically diverse archaeal amoA sequences. Sites with low nitrification rates were dominated by estuarine Nitrosomonas-like amoA sequences and archaeal amoA sequences similar to those previously described in soils. This is the first report measuring AOA and β-AOB amoA abundance in conjunction with (15)N-based nitrification rates in estuary sediments.     

Quantitative analyses of ammonia-oxidizing Archaea and bacteria in the sediments of four nitrogen-rich wetlands in China

With the rapid development of ammonia-synthesizing industry, the ammonia-nitrogen pollution in wetlands acting as the sink of point and diffuse pollution has been increased dramatically. Most of ammonia-nitrogen is oxidized at least once by ammonia-oxidizing prokaryotes to complete the nitrogen cycle. Current research findings have expanded the known ammonia-oxidizing prokaryotes from the domain Bacteria to Archaea. However, in the complex wetlands environment, it remains unclear whether ammonia oxidation is exclusively or predominantly linked to Archaea or Bacteria as implied by specific high abundance. In this research, the abundance and composition of Archaea and Bacteria in sediments of four kinds of wetlands with different nitrogen concentration were investigated by using quantitative real-time polymerase chain reaction, cloning, and sequencing approaches based on amoA genes. The results indicated that AOA distributed widely in wetland sediments, and the phylogenetic tree revealed that archaeal amoA functional gene sequences from wetlands sediments cluster as two major evolutionary branches: soil/sediment and sediment/water. The bacteria functionally dominated microbial ammonia oxidation in different wetlands sediments on the basis of molecule analysis, potential nitrification rate, and soil chemistry. Moreover, the factors influencing AOA and AOB abundances with environmental indicator were also analyzed, and the results addressed the copy numbers of archaeal and bacterial amoA functional gene having the higher correlation with pH and ammonia concentration. The pH had relatively great negative impact on the abundance of AOA and AOB, while ammonia concentration showed positive impact on AOB abundance only. These findings could be fundamental to improve understanding of the importance of AOB and AOA in nitrogen and other nutrients cycle in wetland ecosystems.