Shifting abundances of communities associated with nitrogen cycling in soils promoted by sugarcane harvest systems

Sugarcane cultivation supports Brazil as one of the largest world sugar and ethanol producer. In order to understand the impact of changing sugarcane harvest from manual to mechanized harvest, we studied the effect of machinery traffic on soil and consequently soil compaction upon soil microbial communities involved in nitrogen cycling. The impact of sugarcane harvest was dependent on soil depth and texture. At deeper soil layers, mechanized harvesting increases the abundance of nitrogen fixers and denitrifying communities (specifically nosZ clade I and II) while manual harvesting increases the abundance of ammonia oxidizers (specifically AOA) and increases denitrifying communities (nosZ clade I and II) on top and at intermediate depth. The effect of change on the harvest system is more evident on sandy soil than on clay soil, where soil indicators of compaction (bulk density and penetration resistance) were negatively correlated with soil microorganisms associated with the nitrogen cycle. Our results point to connections between soil compaction and N transformations in sugarcane fields, besides naming biological variables to be used as proxies for alterations in soil structure.     

反硝化除磷戈登氏菌属的富集及其菌剂制备

【背景】投加微生物菌剂是强化生物处理效能的重要手段,反硝化是污水脱氮除磷的关键步骤,但目前对于反硝化微生物菌剂相关的研究报道较少。【目的】驯化高效反硝化聚磷菌菌剂,并对系统进行生物强化。【方法】采用两阶段法快速富集反硝化聚磷菌,筛选高效脱氮除磷功能菌株NC1-1并进行鉴定,以NC1-1为菌种来源制备干粉菌剂,研究菌剂强化A²SBR系统污水处理效果。【结果】历经36 d后反硝化聚磷菌富集成功,菌株NC1-1经鉴定属于戈登氏菌属,其脱氮除磷率分别为89.46%和91.68%。麦麸、玉米粉配比为85%:15%、NC1-1投菌量为20 mL、发酵液用量20 mL的条件下成功制得干粉菌剂,干粉菌剂最佳投加量为10%的A²SBR系统总磷（total phosphorus,TP）和NO₃^--N去除率比未投加菌剂的A²SBR系统提高12.06%和11.52%。【结论】菌剂NC1-1的投加使A²SBR系统的污染物去除效能进一步提高,研究结果为进一步研究反硝化聚磷菌菌剂提供了...     

深海沉积物高效脱氮菌筛选分离及其脱氮特性研究

【背景】深海海域具有高压、低温、无光等环境条件,蕴含着丰富而独特的微生物资源。【目的】从深海沉积物中定向分离、筛选脱氮效率高的好氧脱氮菌株资源,并揭示其脱氮特性,为开发水体脱氮微生物技术提供物质基础。【方法】以东太平洋、南大西洋、西南印度洋共10个站位的深海沉积物为研究材料,在28°C下使用无机氮源连续进行两轮富集培养,然后定性筛选可以脱除氨氮、亚硝态氮和硝态氮的菌株,并通过形态学和16S rRNA基因序列分析进行初步分类鉴定;对优选得到的功能菌株,分别采用以氨氮、亚硝态氮、硝态氮为唯一氮源的培养基定量研究其生长和脱氮性能。【结果】从10份大洋深海沉积物样品中共分离得到49株好氧反硝化菌,其中3株在有氧条件下反硝化效率较高,分别命名为Pseudomonassp.G111、Pseudomonassp.G112和Dietziamaris W023a,其中菌株G111和G112与模式菌株博岑假单胞菌Pseudomonas bauzanensis BZ93T的16S rRNA基因序列相似度为99.2%,菌株W023a与模式菌株海洋迪茨氏菌DietziamarisATCC35013T的16SrRNA基因序列相似度为99.9%。菌株G111、G112和W023a培养48h后,对氨氮的脱除率分别为98.0%、85.2%和97.6%;对亚硝态氮的脱除率分别为71.9%、67.5%和34.7%;对硝态氮的脱除率分别为66.0%、52.6%和56.3%。菌株G111、G112和W023a均为异养硝化-好氧反硝化菌,可通过好氧反硝化作用将亚硝态氮和硝态氮还原为含氮气体,也可通过异养硝化-好氧反硝化作用将氨氮转化为含氮气体。【结论】从深海沉积物中分离筛选得到3株高效好氧反硝化菌,所获得的菌株在水体净化、污水处理、生态系统修复等领域具有应用潜力。     

C/N驱动优势细菌菌群变化影响堆肥碳氮损失和腐殖质合成

为了探明C/N如何驱动堆肥过程中优势细菌菌群的变化而影响碳氮损失和腐殖质合成,设置3个C/N处理(20∶1、25∶1和30∶1),以羊粪和玉米秸秆为原料进行堆肥试验。结果表明: 与20∶1处理相比,30∶1和25∶1处理堆肥的碳、氮损失分别降低了33.5%、18.9%和23.6%、10.8%。优势细菌菌群、碳氮损失及有机碳组分的冗余分析表明,高C/N提高了堆肥中固氮细菌的种类和丰度,降低了反硝化细菌的种类和丰度,减少了堆肥过程中的碳氮损失;高C/N促进了木质纤维素类降解菌的生长繁殖,促进了富里酸和胡敏素降解而合成更多胡敏酸,提高了堆肥腐殖化程度。可见,C/N可通过影响堆肥中关键优势细菌菌群而影响堆肥过程和堆肥质量,调节堆肥原料C/N可以调控堆肥中碳氮损失和腐殖质的合成,从而提高堆肥质量并减少堆肥的二次环境污染。     

Identification of a denitrifying bacterium and verification of its anaerobic ammonium oxidation ability

A strain D3 of denitrifying bacterium was isolated from an anammox reactor,and identi-fied as Pseudomonas mendocina based on the morphological and physiological assay,Vitek test,Biolog test,(G C) mol% content,and 16S rDNA phylogenetic analysis.As a typical denitrifying bac-terium,strain D3 achieved the maximal nitrate reduction rate of 26.2 mg/(L·d) at the nitrate concen-tration of 88.5 mg N/L.The optimal pH and growth temperature were 7.84 and 34.9℃,respectively.Strain D3 was able to oxidize ammonia under anaerobic condition.The maximum nitrate and ammo-nium utilization rates were 6.37 mg/(L·d) and 3.34 mg/(L·d) ,respectively,and the consumption ratio of ammonia to nitrate was 1:1.91.Electron microscopic observation revealed peculiar cell inclusions in strain D3.Because of its relation to anammox activity,strain D3 was presumed to be anammoxosome.The present investigation proved that denitrifying bacteria have the anammox ability,and the results have engorged the range of anammox populations.     

施肥对设施菜地nirK型反硝化细菌群落结构和丰度的影响

采用末端限制性片段多态性分析(T-RFLP)和实时荧光定量PCR(real-time PCR)方法,研究了甘肃武威设施菜地不同施肥条件下0～20 cm、20～40 cm土层中土壤nirK型反硝化细菌群落结构和丰度的变化.结果表明： 施肥对土壤中nirK型反硝化细菌的群落结构具有明显影响,且对70、156、190 bp片段所代表设施菜地土壤优势种群影响最显著.施肥对0～20 cm土层nirK型反硝化细菌丰度有明显影响,其最大值出现在全有机肥(M)处理、为每克干土2.16×10⁷个拷贝数,分别是对照(CK)和全化肥(NPK)处理的2.04和2.02倍.设施菜地土壤0～20 cm与20～40 cm土层nirK型反硝化细菌的优势种群及其基因丰度均存在显著差异,且设施菜地土壤中nirK型反硝化细菌的群落结构和丰度与大田差异明显.土壤pH值、有机质及硝酸盐含量均影响nirK型反硝化细菌的群落结构和丰度.系统发育分析结果表明,土壤中除存在与厌氧反硝化细菌亲缘相近的nirK型反硝化微生物外,还存在与好氧反硝化菌亲缘关系相近的nirK型反硝化微生物,如根瘤菌属、苍白杆菌属、土壤杆菌属等.
     

麦田根际土壤反硝化作用对O_3熏气和太阳辐射减弱的响应

为研究臭氧浓度升高和太阳辐射减弱复合背景下,麦田土壤反硝化作用及N2O排放的变化,采用开顶箱(OTC)法和遮光网技术,设置3个臭氧浓度梯度及3个辐射减弱梯度,连续4a对小麦生长季麦田土壤进行臭氧浓度增加太阳辐射减弱以及它们的复合作用的试验。采用MPN(最大或然数)法测定反硝细菌的数量,用气相色谱法测定反硝化强度。结果显示反硝化细菌数量和反硝化强度受小麦生长发育的影响,在小麦成熟期收割后土壤反硝化细菌数量和反硝化强度增加得特别明显。O3连续作用3个生长季后,以及太阳辐射减弱处理,土壤反硝化菌和反硝化强度显著升高,N2O排放量显著增加。减弱的太阳辐射与增加的O3复合作用,在小麦的每个生育期均显著促进了反硝化菌数量增加和反硝化强度增强,促进率显著高于O3和遮荫的单独作用。结果说明,O3浓度增加以及太阳辐射减弱对土壤反硝化菌和反硝化强度均有一定的促进作用,减弱的太阳辐射与高浓度的O3两因素之间存在协作关系,太阳辐射减弱有利O3的吸收,增加O3伤害,促进反硝化过程。     

Identification and comparison of aerobic and denitrifying polyphosphate-accumulating organisms

Two laboratory-scale sequencing batch reactors (SBRs) were operated for enhanced biological phosphorus removal (EBPR) in alternating anaerobic-aerobic or alternating anaerobic-anoxic modes, respectively. Polyphosphate-accumulating organisms (PAOs) were enriched in the anaerobic-aerobic SBR and denitrifying PAOs (DPAOs) were enriched in the anaerobic-aerobic SBR. Fluorescence in situ hybridization (FISH) demonstrated that the well-known PAO, "Candidatus Accumulibacter phosphatis" was abundant in both SBRs, and post-FISH chemical staining with 4,6-diamidino-2-phenylindol (DAPI) confirmed that they accumulated polyphosphate. When the anaerobic-anoxic SBR enriched for DPAOs was converted to anaerobic-aerobic operation, aerobic uptake of phosphorus by the resident microbial community occurred immediately. However, when the anaerobic-aerobic SBR enriched for PAOs was exposed to one cycle with anoxic rather than aerobic conditions, a 5-h lag period elapsed before phosphorus uptake proceeded. This anoxic phosphorus-uptake lag phase was not observed in the subsequent anaerobic-aerobic cycle. These results demonstrate that the PAOs that dominated the anaerobic-aerobic SBR biomass were the same organisms as the DPAOs enriched under anaerobic-anoxic conditions.     

采伐剩余物管理对杉木人工林土壤nosZ型反硝化细菌群落多样性的影响

反硝化细菌是土壤氧化亚氮(N₂O)排放的关键因子。以杉木人工林为研究对象,设置4种采伐剩余物处理方式(RF:对照;RB:火烧;MT:粉碎;NR:移除),采用高通量测序技术,以nosZ为标记基因,测定了自2018年9月—2020年9月,2年期间土壤nosZ型反硝化细菌群落的组成和丰度。研究结果显示,4种采伐剩余物处理中的土壤nosZ型反硝化细菌90%以上来自变形菌门,优势菌属包括固氮螺菌属、中慢生根瘤菌属、动胶菌属、伯克霍尔德菌属、嗜酸菌属、慢生根瘤菌属、假单胞菌属、固氮弧菌属以及无色杆菌属;样本间差异物种的显著性分析表明,在处理完成半年时,火烧相较于对照于β-变形菌纲水平显著增加了nosZ基因丰度;在处理完成一年时,火烧分别于红螺菌目、红螺菌科、固氮螺菌属水平显著高于粉碎;粉碎相较于移除在处理完成一年时,于γ-变形菌纲和产碱菌科水平显著增加了nosZ基因丰度;在处理完成两年时,粉碎处理的nosZ基因丰度在变形菌门水平显著高于对照和火烧。α多样性数据显示,处理完成一年时,粉碎处理相较于对照和移除显著增加了Shannon和Simpson指数;处理完成两年时,粉碎和火烧...     

Molecular analysis of microbial population transition associated with the start of denitrification in a wastewater treatment process

AIMS: The objective of this study is to determine the bacteria playing an important role in denitrification by monitoring the molecular dynamics accompanying the start of denitrification. METHODS AND RESULTS: cDNA reverse-transcribed from 16S rRNA was amplified with fluorescent labelled primer for terminal restriction fragment length polymorphism (T-RFLP) analysis and an unlabelled primer for cloning analysis. The terminal restriction fragments (T-RFs) that increased in association with the start of denitrification were determined. These T-RFs were identified by in silico analysis of 16S rRNA sequences obtained from cloning. As a result, it was clearly observed that the bacteria belonging to the genera Hydrogenophaga and Acidovorax increased in number after the start of denitrification. CONCLUSIONS: It was demonstrated that T-RFLP analysis targeting 16S rRNA is appropriate for the daily monitoring of a bacterial community to control wastewater treatment processes. Combination of the results of T-RFLP analysis and 16S rRNA clone library indicated that the bacteria belonging to the genera Hydrogenophaga and Acidovorax play an important role in denitrification. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide new insight to the 16S rRNA level of active denitrifying bacteria in wastewater treatment processes.