Chronic Nitrogen Fertilization Modulates Competitive Interactions Among Microbial Ammonia Oxidizers in a Loess Soil

Nitrogen(N) application may lead to niche segregation of soil ammonia-oxidizing archaea(AOA) and bacteria(AOB), thereby reducing the competitive interactions between AOA and AOB due to higher ammonium substrate availability. However, the adaptive mechanisms of AOA and AOB under N enrichment remain poorly understood. Stable isotope probing(SIP) microcosm incubation was employed to reveal community changes of active AOA and AOB in a loess soil from a field experiment growing potatoes that received no N(control, CK), low N(LN, 75 kg N ha~(-1)), and high N(HN, 375 kg N ha~(-1)). The results showed that the soil potential nitrification rate(PNR) was measured by culturing of the soil samples from the field experiment. Soil PNR was significantly increased in HN by87.5% and 67.5% compared with CK and LN, respectively. Compared with CK, the~(13)C-amoA genes of soil AOA and AOB in HN had 2.58 × 10~4 and 1.55 × 10~6 copies, representing 1.6-and 16.2-fold increase respectively. It was indicated that AOB dominated soil ammonia oxidation. A phylogenetic analysis of the~(13)C-amoA gene showed that N application significantly increased the proportion of54 d9-like AOA up to 90% in HN, while the Nitrososphaera gargensis-like and Nitrososphaera viennensis-like AOA were inhibited and completely disappeared. Nitrogen application also resulted in the community shift of active AOB-dominant group from Nitrosospira briensis-like to Nitrosospira sp. TCH711-like. Our study provides compelling evidence for the emergence and maintenance of active nitrifying communities under the intensified N input to an agricultural ecosystem.     

Effects of herbicide butachlor application on the growth of periphytic biofilms and nitrogen loss in paddy systems

The application of butachlor as an herbicide in paddy fields is widely practiced,aiming to increase rice yield by directly or indirectly influencing the paddy environment.Periphytic biofilms,which form at the soil-water interface in paddy fields,are complex bioaggregates that play an important role in nitrogen (N) cycling.The objective of this study was to investigate the effect of butachlor on periphytic biofilm growth and N cycling under both light and dark conditions in the laboratory.The res...     

共固定化亚硝化-反硝化细菌工艺及特性研究

以亚硝化细菌、反硝化细菌为研究对象,采用共固定化细胞技术,以海藻酸钠共固定化亚硝化-反硝化细菌,研究了共固定化工艺条件及其在模拟污水中的脱氮效果。结果表明,共固定化亚硝化-反硝化细菌最佳工艺条件为4.5%海藻酸钠和2.1%氯化钙共固定化细胞,接种量为3个/m L培养基,接种于装有140 m L模拟污水液体培养液的250 m L三角瓶中,最佳p H为8,最佳培养温度30℃,110~140 r/min培养。54 h时氨氮去除率为95.95%,78 h时亚硝态氮去除率为95.82%。共固定化小球可重复使用3次、低温对共固定化后菌种脱氮性能的影响较小。     

有机废弃物好氧堆肥系统中氨氧化微生物的研究进展

好氧堆肥是一种经济高效的有机废弃物处理技术,在堆肥过程中氨氧化作为氮素硝化作用的限速步骤,直接或间接影响堆肥过程中温室气体的排放和堆肥肥效。论文介绍了有机废弃物好氧堆肥系统中两种氨氧化微生物氨氧化古菌(AOA)和氨氧化细菌(AOB)的生理生态特性,概述了堆温、铵离子浓度、pH等因素对堆肥过程中氨氧化微生物种类、数量及群落结构的影响,总结了堆肥过程中调控氨氧化微生物对氮素转换作用的相关措施,并展望了氨氧化微生物在有机废弃物堆肥系统中的应用前景。     

Earthworm regulation of nitrogen pools and dynamics and marker genes of nitrogen cycling: A meta-analysis

Earthworms, as the ecosystem engineers, both directly and indirectly affect the nitrogen(N) cycle. We aimed to provide a quantitative assessment of the contribution of earthworms to the terrestrial ecosystem N cycle using meta-analysis of 130 publications selected. The natural logarithm of the response ratio(lnRR) was used to indicate the effect size of earthworms on N dynamic variables. The results showed that earthworms significantly affected soil N-cycling microorganisms, including the amoA gene abundance of soil ammonia-oxidizing bacteria(AOB), and significantly promoted soil N cycle processes,including denitrification, mineralization, and plant assimilation. The effects of earthworms on the N cycle were experimental design dependent and affected by factors such as the functional group of earthworm and residue input. The presence of the anecic earthworms decreased the rates of mineralization and nitrification, and increased nitrification and denitrification responses were more pronounced in the presence of the endogeic earthworms than that of the other two functional groups of earthworms. In addition, residue input enhanced the effects of earthworms on the N cycle. The effects of earthworms on nitrous oxide(N₂ O) emission increased when residues were added. These findings indicate that residue input and introducing suitable functional groups of earthworms into the field can lead to N sustainability without increasing N2 O emission. This meta-analysis also provides systematic evidence for the positive effects of earthworms on the plant N pool, N availability(soil ammonium(NH₄⁺) content), and soil microbial biomass N content, showing the potential to alter ecosystem functions and services in relation to N cycling.     

Improvement of media for thermophilic ammonia-oxidizing bacteria in compost

Thermophilic ammonia-oxidizing bacteria (AOB) have the potential to reduce ammonium emissions from commercial-scale animal waste composting operations. Two new media have been designed to culture and enumerate thermophilic AOB species. C-1 medium was designed to reflect compost composition. C-2 medium and CQ-2 medium were modified synthetic organic wastewater for the cultivation and enumeration of AOB, respectively. These new media have several advantages over the conventional medium. C-2 medium is effective for nitrification at 50°C, and C-1 and C-2 media support reasonable growth of thermophilic AOB. Furthermore, C-1 and CQ-2 media allow enumeration of thermophilic AOB during the composting process. This is the first report of the successful cultivation and enumeration of thermophilic AOB in compost. These results suggest the possibility of isolation and manipulation of novel thermophilic AOB species for environmental bioremediation.     

西南地区pH影响紫色土硝化作用机制研究

硝化作用是一个对pH高度敏感的典型过程,但pH影响土壤硝化作用的机制尚不完全明了。本研究以西南地区3种发育于同一母质的不同pH的紫色土(酸性紫色土 pH=5.7,中性紫色土 pH=7.3,石灰性紫色土 pH=8.0)作为供试材料,研究pH对紫色土硝化强度及氨氧化微生物的长期效应;通过人为添加酸(H₂SO₄)或碱(NaOH)短期改变土壤pH的方法,研究pH对紫色土硝化作用强度、氨氧化微生物活性及丰度的短期效应。结果表明,pH的短期改变对酸性与石灰性紫色土的硝化作用无显著影响(P>0.05),但对中性紫色土的硝化速率影响显著(P<0.05);氨氧化古菌(AOA)的amoA基因在酸性土壤环境中的表达更高(3.04×10⁸/g干土,AOA/AOB=31.8),而氨氧化细菌(AOB)则更适应于石灰性紫色土环境(2.35×10⁸/g干土,AOA/AOB=0.07)。研究表明,紫色土的硝化作用强度受pH的影响显著,且在不同pH土壤中其作用机制各不相同。硝化微生物群落和活性主导了酸性和石灰性紫色土中的硝化作用,而中性紫色土中的硝化作用则是由底物浓度所主导。研究推测长期稳定的pH是影响硝化微生物群落和活性的关键因素,而pH的短期改变则主要影响硝化反应的底物有效性。     

Changes in the composition and diversity of topsoil bacterial,archaeal and fungal communities after 22 years conventional and no-tillage managements in Northern China

A comprehensive comparison about microbial community (bacterial, archaeal and fungal) response to different tillage managements in Northern China remain little studied, in this study we compared no-tillage (NT) versus conventional tillage (CT) management on topsoil microbial community diversity and composition in field experiment. We found that NT practice significantly increased the soil moisture content (SMC), bulk density, stocks of soil organic carbon (SOC), total nitrogen (TN), and microbial biomass carbon and nitrogen (P < 0.05). Moreover, higher levels of bacterial and archaeal alpha diversity were observed in NT relative to CT while unexpectedly, there was no significant difference found in fungal diversity between two treatments. The most pronounced shifts in the composition of the different microbial groups were found for the archaeal community, which followed by bacterial and fungal. NT practice markedly enhanced abundances of Proteobacteria (belongs to bacteria) phyla, Thaumarchaeota phyla (belongs to archaea) and Glomeromycota phyla (belongs to fungi). Redundancy analysis revealed that the factor that most closely correlated with bacterial, archaeal and fungal composition were SMC, TN and SOC, respectively. Considering NT enhanced both microbial composition and C storage in topsoil, we suggest that NT offers significant promise to improve topsoil health in this region.     

杉木连栽氨氧化古菌群落结构与硝态氮含量的关系

目的 分析不同代数杉木林的土壤有效氮含量变化,探讨硝态氮与不同分类水平的氨氧化古菌（AOA）群落结构、多样性之间的联系,为人工林土壤氮素的有效性和杉木林土壤质量评估提供参考。 方法 在福建南平选取4个代数的杉木人工林,采用高通量测序技术对 PCR 扩增的 amoA 基因进行测定,运用 Mantel_r 相关分析、随机森林模型和偏最小二乘路径模型等分析方法研究不同代数的土壤有效氮含量与氨氧化古菌群落丰度、多样性之间的关系。 结果 随杉木连栽代数增加,硝态氮（NO3−-N）含量显著下降,铵态氮（NH4+-N）和微生物量氮（MBN）含量变化不明显。土壤酶活性、氨氧化古菌群落丰度与多样性总体呈降低趋势,土壤有效氮含量与氨氧化古菌群落以及酶活性之间联系密切,其中,氨氧化古菌丰度与多样性指数是影响硝态氮含量的最主要因素。 结论 随着连栽代数增加,氨氧化古菌群落的丰富度与多样性一定程度上降低,除第4代土壤脲酶和氨单加氧酶活性略有上升,土壤氮循环相关酶活性基本呈降低趋势,从而导致土壤硝态氮含量显著降低,限制了杉木连栽林土壤氮素的有效性。