基于响应面法对一株好氧反硝化菌脱氮效能优化

【目的】水体富营养化是当今我国水环境面临的重大水域环境问题,氮素超标排放是主要的引发因素之一。好氧反硝化菌构建同步硝化反硝化工艺比传统脱氮工艺优势更大。获得高效的好氧反硝化菌株并通过生长因子优化使脱氮效率达到最高。【方法】经过序批式生物反应器(Sequencing batch reactor,SBR)的定向驯化,筛选获得高效好氧反硝化菌株,采用响应面法优化好氧反硝化过程影响总氮去除效率的关键因子(碳氮、溶解氧、pH、温度)。【结果】从运行稳定的SBR反应器中定向筛选高效好氧反硝化菌株Pseudomonas T13,采用响应面法对碳氮比、pH和溶解氧关键因子综合优化获得在18 h内最高硝酸盐去除率95%,总氮去除率90%。该菌株的高效反硝化效果的适宜温度范围为25?30 °C;最适pH为中性偏碱;适宜的COD/NO3?-N为4:1以上;最佳溶解氧浓度在2.5 mg/L。【结论】从长期稳定运行的SBR反应器中筛选获得一株高效好氧反硝化菌Pseudomonas T13,硝酸盐还原酶比例占脱氮酶基因的30%以上,通过运行条件优化获得硝氮去除率达到90%以上,对强化废水脱氮工艺具有良好应用价值。     

异养硝化-好氧反硝化菌脱氮相关酶系及其编码基因的研究进展

水体氮素污染日益严重,如何经济、高效地去除水体氮素已成为研究热点。近年来,研究人员已从不同环境中分离到许多同时具有异养硝化和好氧反硝化功能的菌株,此类菌生长迅速,可在好氧条件下同时实现硝化和反硝化的过程,并可用于脱除有机污染物,是一类应用潜力巨大的脱氮菌。目前,异养硝化-好氧反硝化菌的脱氮途径和机制主要是通过测定氮循环中间产物或终产物、测定相关酶活性、注释部分氮循环相关基因及参考自养硝化菌和缺氧反硝化菌的氮循环途径等进行研究,其完整的氮素转化途径和氮代谢机制还需要进一步明确。总结了目前异养硝化-好养反硝化菌的脱氮相关酶系及其编码基因的研究进展,以期为异养硝化-好氧反硝化菌的理论研究及其在污水脱氮处理上的应用提供参考。     

新型异养硝化-好氧反硝化菌Paracoccus sp. QD-19的分离及脱氮特性研究

从沈阳市南部污水处理厂活性污泥中分离获得同时具备异养硝化和好氧反硝化能力的新型菌株,研究其脱氮特性,为改善污水厂的脱氮处理工艺奠定基础。对菌株进行形态学观察和16S rRNA基因鉴定;分别以NH₄Cl、NaNO₂、KNO₃为唯一氮源探究菌株的脱氮能力;以碳源、C/N比、pH值、温度、转速、接种量(V∶V)等因素对菌株脱氮效果的影响进行研究。获得一株新型异养硝化-好氧反硝化菌株,经16S rRNA基因序列比对为副球菌属(Paracoccus),命名为Paracoccus sp. QD-19。菌株对初始氨氮浓度在300 mg/L以下的低浓度氨氮去除率能够达到100%,去除速率为8.707 mg/(L·h)且在脱氮过程中几乎没有亚硝态氮和硝态氮的积累。以亚硝态氮和硝态氮作为唯一氮源时,对此两种氮源的去除率36 h内均能达到99%,去除速率分别为4.944和5.666mg/(L·h)。确定了去除氨氮的最佳脱氮条件：琥珀酸钠为碳源,C/N比为10,pH值为7,接种量(V:V)为1%,温度为30℃,转速为140 r/min。菌株Pa...     

耐高浓度氨氮的异养硝化好氧反硝化菌株U1的鉴定及其脱氮特性

【背景】城市垃圾渗滤液是一种成分复杂的有机废水,含氮量高,如果未经处理直接排放到环境中会造成严重的环境污染。【目的】筛选可以耐受垃圾渗滤液中高浓度氨氮并高效去除污水中氮素的异养硝化好氧反硝化菌株,为解决垃圾渗滤液的氮素污染提供功能菌株。【方法】从垃圾渗滤液中筛选分离能耐受高氨氮浓度的菌株,通过测定各菌株的脱氮能力,筛选到一株脱氮能力最强的菌株,命名为U1,通过测定16S rRNA基因序列和生理生化特性确定该菌株为铜绿假单胞菌。进一步研究了菌株U1在不同初始氨氮浓度、碳源、转速、初始pH、碳氮比等单因素变量下的脱氮能力,并结合L₉（3⁴）正交试验研究了菌株U1的最佳脱氮条件。【结果】分离出一株铜绿假单胞菌并命名为U1。该菌株的最优脱氮条件为:初始氨氮浓度为1 000 mg/L,红糖和柠檬酸三钠的混合碳源,pH 6.0,C/N为10,转速为130 r/min,菌株U1的最大总氮去除率为64.37%,最大氨氮去除率为76.73%。对于总氮和氨氮含量分别是2 345 mg/L和1 473.8 mg/L的垃圾渗滤液,菌株U1最大总氮去除率为27.86%...     

好氧甲烷氧化耦合反硝化极限脱氮系统的效能及应用

【目的】探究甲烷浓度、温度和氮浓度对好氧甲烷氧化耦合反硝化(AME-D)极限脱氮系统的影响,分析该系统微生物群落结构,并对贵阳某污水处理厂尾水进行应用研究。【方法】采用阶段性实验研究甲烷浓度、温度和氮浓度对系统脱氮效能的影响,通过16SrRNA基因测序技术分析系统中微生物群落结构,利用共焦显微拉曼光谱仪分析实际废水水质变化特征。【结果】甲烷进气比为3%、温度为30°C、氮浓度为20 mg/L时脱氮效果最好,系统的总氮、氨氮和硝酸盐氮平均去除率分别为93.66%、96.13%和92.25%;系统中的主要甲烷氧化菌分别为Methylosarcina(1.84%)、Methylovulum(0.01%)和Crenothrix(0.14%),以及兼性甲烷氧化菌属Methylocystis(1.9%),主要的亚硝化菌为Nitrosomonas(0.008%),硝化菌为Nitrospira (0.42%),反硝化菌为Hyphomicrobium (1.19%)和Pseudomonas (0.61%);采用该系统处理贵阳某污水处理厂尾水时,出水总氮平均浓度达到0.96mg/L,能达到极限脱氮的目的,拉曼光谱分析显示系统对硝酸盐氮和亚硝酸盐氮有较高的去除,甲烷被氧化形成的中间产物可能为醇类或醛类物质,为反硝化菌提供所需碳源。【结论】AME-D极限脱氮由多种微生物协同实现,其功能微生物为甲烷氧化菌、亚硝化菌、硝化菌和反硝化菌,应用研究显示该系统在城镇污水处理系统中具有较大的应用潜力。     

一株海水异养硝化-好氧反硝化菌系统发育及脱氮特性

【目的】确定一株分离自海水的异养硝化-好氧反硝化菌的系统发育地位并探索其脱氮特性和机理,以期为解释异养硝化-好氧反硝化机理以及改进海水养殖及废水的生物脱氮工艺提供理论依据。【方法】通过形态观察、生理生化实验和16S rRNA基因序列分析,鉴定该菌株;通过测定菌株在不同无机氮源降解测试液中的生长和脱氮效率,分析其异养硝化和好氧反硝化性能。【结果】经鉴定该菌株属于盐单胞菌属(Halomonas);最适生长条件为盐度3%、pH 8.5、温度28℃、碳氮比10:1,在盐度为15%的培养液中仍能生长;可以同时去除氨氮、亚硝酸氮和硝酸氮,24 h时对NH4+-N、NO2--N、和NO3--N的去除率可分别达到98.29%、99.07%、96.48%,3种形态无机氮同时存在时,会优先利用NH4+-N,且总无机氮去除率较单一存在时更高,说明该菌株可实现同步硝化反硝化。【结论】该分离自海水的异养硝化-好氧反硝化菌属于盐单胞菌属(Halomonas),在高盐环境中仍能生长,同时具有高效的异养硝化和好氧反硝化能力,能够独立完成脱氮的全部过程。     

一株轻度嗜盐反硝化细菌的分离鉴定和反硝化特性初探

从处理高盐度废水的成熟活性污泥中分离筛选得到1株轻度嗜盐反硝化细菌GYL, 通过对该菌株的形态观察、生理生化实验以及16S rDNA序列分析, 确定该菌株为盐单胞菌(Halomonas sp.)。该菌株能在盐度为10%的培养液中生长, 最适盐度为2%~7%, 最适pH为7.5~8.5, 最佳碳源为蔗糖, 在25°C~30°C的温度范围内脱氮效率达到80%以上。对该菌株的异养硝化能力进行了测定, 其对氨氮的去除率可达98.3%, 说明该菌株可实现同步硝化反硝化, 即该菌可以独立完成生物脱氮的全部过程。     

好氧反硝化细菌SY-D-22的分离、优化及脱氮机理

【背景】在处理含硝酸盐氮的废水中,常见微生物不能同时高效去除硝酸盐氮和总氮,导致处理废水时往往使用多种微生物复合菌剂或者使用复杂的工艺。【目的】高效、安全地去除水中的硝酸盐氮和总氮。方法】富集筛选出一株新型高效好氧反硝化细菌,对其进行16S rRNA基因鉴定。利用响应面法对其影响脱氮因素进行优化并探索其最佳脱氮条件。研究其对含硝酸盐氮废水的反硝化能力及脱氮特性。【结果】从活性污泥中筛选获得一株新型高效好氧反硝化细菌SY-D-22,经鉴定为葡萄球菌属(Staphylococcus)。响应面法优化其最佳反硝化条件为：pH 8.18,C/N为13.39,温度31.43°C,摇床转速130 r/min。当以最佳碳源柠檬酸钠为唯一碳源时,对于100 mg/L浓度的NO₃^--N去除率可达100%,同时对于总氮(total nitrogen,TN)的去除率为95.34%,具有高效脱氮能力。【结论】从活性污泥中筛选出一株新型好氧反硝化细菌Staphylococcus SY-D-22,通过响应面法条件优化,菌株的硝酸盐氮去除率达到100.00%,总氮去除率达到...     

人工湿地氮去除关键功能微生物生态学研究进展

人工湿地是一种能有效处理水体氮素污染的生态技术,其中微生物是驱动人工湿地系统中氮素去除的重要引擎。近20年来,随着分子生物学技术的广泛应用,有关人工湿地氮去除功能微生物生态学方面研究取得了一些重要进展。以硝化-反硝化作用和厌氧氨氧化作用这两种重要的人工湿地微生物脱氮途径为主,针对氨氧化细菌/古菌、厌氧氨氧化菌和反硝化菌等关键脱氮功能微生物的研究,重点归纳总结了目前有关这几类关键功能菌群在人工湿地中的丰度、活性、多样性、分布特征与影响因素,及其对废水中氮去除的作用,并在此基础上对今后的重点研究工作提出了展望。面向未来人工湿地氮去除关键功能微生物的研究应侧重其在污水净化和温室气体减排等方面的生态功能研究,同时加强其代谢过程与机制以及不同功能菌群间的关联研究。     

好氧反硝化菌的筛选及其脱氮除磷性质的研究

利用富集培养基, 从用生活污水驯化后的活性污泥中筛选得到一株具有好氧反硝化兼具除磷功能的细菌。通过形态学及生理生化指标鉴定其为假单胞菌属。利用此好氧反硝化菌处理模拟废水及生活废水, 通过监测总氮、无机磷及CODcr变化确定在C/N摩尔比为3:1、接种量为10%、pH 6.8、30°C条件下处理2 d, 该菌株脱氮、除磷及去除有机物的效果最佳, 活性污泥经此好氧反硝化菌强化后, 对生活废水的处理能力得到明显提升。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.