秦岭太白山区6种中草药根际与非根际土壤化学性质及酶活性

以秦岭太白山区不同生境下鹿蹄草、三尖杉、玉竹、银露梅、珠芽蓼和金露梅6种中草药为对象,研究其根际与非根际土壤的化学性质及酶活性.结果表明:6种中草药根际土壤的有机质、全氮、有效氮、有效磷含量和阳离子交换量(CEC)均高于非根际土壤,呈现明显的根际聚集现象;土壤酶活性总体上表现出根际较强的特性;土壤有机质、全氮、全磷含量与中性磷酸酶呈显著正相关;土壤CEC与中性磷酸酶和酸性磷酸酶均呈显著正相关.6种中草药非根际土壤的有机质、全氮与脲酶、过氧化氢酶和中性磷酸酶均呈显著正相关;土壤CEC与脲酶、过氧化氢酶、中性磷酸酶和酸性磷酸酶均呈显著正相关.根际土壤肥力水平综合得分总体上大于非根际土壤.其中,金露梅、珠芽蓼和银露梅的根际与非根际土壤肥力水平综合得分较高,而鹿蹄草、玉竹和三尖杉得分较低.土壤有机质和CEC在评价6种中草药根际与非根际土壤肥力中起重要作用,而中性磷酸酶是首选土壤酶指标.     

西宁南山4种灌木根际和非根际土壤微生物、酶活性和养分特征

西宁南山区植被退化情况严重,人工造林植被恢复被看作是最有效的恢复手段,其中选择合适造林树种尤为关键。选择人工种植的唐古特白刺Nitraria tangutorum、柠条Caragana korshinskii、西北小蘗Berberis vernae和短叶锦鸡儿Caragana brevifolia共4种灌木树种造林试验区为研究对象,通过测定根际和非根际土壤微生物数量、酶活性及养分含量,综合比较种植4种灌木树种根际和非根际土壤肥力差异,科学评价其对土壤的改善效果。研究表明:(1)土壤微生物数量和酶活性总体呈现出根际高于非根际的规律,仅放线菌数量和脲酶活性出现了根际低于非根际现象。(2)土壤养分方面,4种灌木根际土壤和非根际土壤p H值、全N、全P、全K含量差异不显著,有机质、有效P、速效K含量均呈现出根际非根际,而碱解N则是根际非根际。(3)土壤酶活性与土壤微生物数量相关性不显著,土壤有机质含量与土壤细菌、真菌数量呈极显著正相关,有效P含量与土壤细菌、真菌和放线菌数量呈极显著正相关,速效K含量与过氧化氢酶、酸性磷酸酶活性呈显著正相关,全N、碱解N含量均与脲酶活性呈显著正相关。(4)从土壤肥力综合水平来看,根际非根际,其中根际土壤中西北小蘗柠条短叶锦鸡儿唐古特白刺,研究结果表明西北小蘗和柠条能大幅提高土壤肥力,改良土壤效果较好。     

不同年限茶树根际土壤微生物群落PLFA生物标记多样性分析

以1年生、6年生与20年生茶树根际土壤为研究对象,利用磷脂脂肪酸(PLFAs)生物标记法,对不同年限茶树根际土壤微生物多样性进行了研究.结果表明:6年生茶树根际土壤的PLFA总量最大,其细菌、放线菌与原生动物的PLFA含量高于其他土壤样品;20年生茶树根际土壤的真菌PLFA含量高于其他土壤样品,细菌PLFA含量与1年生茶树根际土壤相近(P＞0.05),放线菌与原生动物PLFA含量均低于其他土壤样品(P＜0.01);在20年生茶树土壤中,一些参与土壤物质循环的微生物类群的丰度在下降,一些代谢能力低的类群丰度增加;土壤酶活性分析结果表明,与6年生茶树土壤相比,20年生茶树土壤的脲酶、酸性磷酸单酯酶与过氧化物酶活性较低,蔗糖酶与多酚氧化酶活性较高;通过相关性分析发现,不同年限茶树土壤细菌、放线菌、真菌、原生动物各总PLFA与酶活性、土壤肥力因子之间密切相关;随着茶树种植年限的增加,茶树根际土壤的微生物群落结构发生了较大的变化,体现在微生物群落的多样性降低,适应于贫瘠条件与低代谢能力的种群增多,反映出根际土壤质量与一些关键酶活性出现较大幅度下降.     

套作棉根际与非根际土壤酶活性和养分的变化

在棉麦两熟双高产条件下研究了棉花根际与非根际土壤酶活性和养分含量的变化.结果表明,套作棉土壤脲酶、蔗糖酶、蛋白酶及过氧化氢酶活性随生育进程的变化趋势与单作棉表现一致,但整个生育期套作棉根际与非根际土壤各种酶活性均明显高于单作棉.套作棉根际与非根际土壤养分含量在麦棉共生期低于单作棉或差异较小,而在麦收后则显著高于单作棉.套作棉土壤养分含量随生育进程的变化趋势与单作棉大体相同,但一些养分的吸收高峰晚于单作棉.无论套作棉还是单作棉,根际土壤酶活性和养分含量高于非根际.土壤各养分含量与土壤脲酶、蔗糖酶和蛋白酶活性呈显著(P=0.0,n=32)或极显著(P=0.01,n=32)相关,与土壤过氧化氢酶活性相关不显著.     

玉米根际与非根际解磷细菌的分布特点

植物光合作用产物约有 12 %～ 5 0 %通过根系进入根际土壤中 ,不同的植物 ,同一植物不同的生长发育时期 ,不仅根际分泌物的数量有差异 ,而且分泌物的种类也不同[4 ] 。这些分泌物不仅是微生物很好的培养基 ,而且一些分泌物可能抑制或有利于甚至刺激某些微生物的繁殖 ,从而导致根际微生物种群结构的变化。根际微生物的数量、活性和群落结构及其变化 ,直接影响到植物吸收水分、养分 ,也影响植物对恶劣环境的抵抗能力 ,尤其是与病菌的侵入和感染关系非常密切[6] 。Ｐ是植物最重要的营养元素之一 ,大多数土壤都具有很强的固定Ｐ的能力 ,Ｐ肥的利…     

铜陵铜矿区凤丹根际和非根际土壤酶活性

对铜陵铜矿区凤丹根际和非根际土壤酶活性特征进行了研究.结果表明,凤丹根际土壤各种酶活性显著大于非根际土壤.凤丹非根际土壤过氧化氢酶、磷酸酶和脲酶活性能敏感地反映土壤重金属复合污染状况;根际环境对土壤酶活性的影响表现为: 磷酸酶＞脲酶＞过氧化氢酶＞蔗糖酶＞多酚氧化酶,影响率分别为131.562%、92.492%、87.557%、59.673%34.076%;土壤各种酶活性与重金属复合污染程度呈显著负相关,相关系数均-0.868以上,表现出重金属复合污染对土壤酶活性的抑制效应.凤丹可有效地改善土壤环境,提高土壤各种酶的活性.     

施用胶质芽胞杆菌菌剂对黑麦草根际土壤脲酶、磷酸酶及过氧化氢酶活性的影响

土壤酶活性是反映土壤肥力最为重要的生物学指标之一。采用稀释涂布平板法研究了从玉米（K02）、草地早熟禾（K05）、披碱草（K09）、多年生黑麦草（K11）、匍匐翦股颖（K12）根际土壤中分离到的5株胶质芽胞杆菌菌株对黑麦草根际土壤脲酶、磷酸酶及过氧化氢酶活性的影响。结果表明：在苗期、中期、收获期各处理黑麦草根际土壤脲酶、磷酸酶和过氧化氢酶活性均高于对照（P〈0.05）。总体来看,各处理黑麦草根际土壤脲酶和过氧化氢酶活性呈先增加后降低的变化趋势;土壤磷酸酶活性与对照（CK）相比除苗期处理K12外,其他处理均呈上升趋势,以处理K05磷酸酶活性最大。研究表明,施入胶质芽胞杆菌菌剂对黑麦草根际土壤脲酶、磷酸酶及过氧化氢酶活性有一定的积极作用,其结果可为生物钾肥的研制提供必要的数据。     

苞箭竹根际土壤微生物数量与酶活性

缺苞箭竹是四川西部亚高山针叶林下层重要的优势植物种群。对缺苞箭竹根际土壤微生物数量与酶活性进行了研究。结果表明,各龄级缺苞箭竹根际土壤细菌、真菌数量显著高于非根际土,而放线菌数量无显著差异,土壤酶活性比值(R/S值)平均分别为2.36、2.08和1.08。各龄级缺苞箭竹根际土壤酸性磷酸酶、蛋白酶、蔗糖酶、脲酶、过氧化氢酶以及多酚氧化酶等酶活性均显著高于非根际土,R/S值平均分别为1.48、1.57、2.14、1.37、1.98和1.67。各龄级缺苞箭竹间相比较,根际土壤中的细菌、真菌数量及各土壤酶活性总体上表现3、5、7龄>9、11、13龄>1龄竹,而放线菌数量在各龄级之间无显著变化,即箭竹在幼龄阶段(1~5龄)随竹龄增加根际微生物数量与酶活性逐渐增加,以后随竹龄老化,根际微生物数量和酶活性逐渐降低。     

施氮量对夏玉米根际和非根际土壤酶活性及氮含量的影响

在华北平原潮土上进行田间试验,研究施氮量对夏玉米根际和非根际土壤酶活性及氮含量的影响.结果表明: 不同施氮水平下土壤酶活性均表现出一致的季节性变化趋势.与不施氮处理相比,施氮处理能显著提高根际和非根际土壤硝态氮含量及根际土壤铵态氮含量,显著增强土壤几丁质酶、β-葡萄糖苷酶、纤维素酶和木聚糖酶活性.在整个玉米生育期内,非根际土壤硝态氮含量显著高于根际土壤;非根际土壤铵态氮含量在灌浆期显著高于根际土壤,但在苗期和完熟期则显著低于根际土壤;根际土壤几丁质酶、β-葡萄糖苷酶、纤维素酶和木聚糖酶活性都显著高于非根际土壤.施氮对土壤有机质含量没有显著影响;在0～180 kg·hm^-2施氮范围内,施氮可明显增加土壤全氮含量,但当施氮量超过180 kg·hm^-2时,土壤全氮含量则明显下降.综上,适量施氮能显著增强土壤酶活性,提高土壤全氮含量,改善土壤生化性质.     

毛竹根际与非根际土壤重金属、理化性质及酶活性特征

于2014年2月至2015年1月在浙江省衢州市铅锌矿附近毛竹林地采集土样,对土壤重金属含量、pH以及土壤酶活性等的动态变化特征进行了研究。结果表明:根际土与非根际土的p H在1a中变化均不明显,且变化范围都处在4.50—4.85之间;非根际土的土壤含水率大于根际土,两者的变化幅度较大,最低值均出现在6月和10月;根际土中Zn和Cd的有效态含量远高于非根际土,而Pb的有效态含量则表现出非根际土大于根际土的特点;过氧化氢酶、磷酸酶、脲酶和脱氢酶在根际土中的活性明显高于非根际土;从土壤重金属有效态与土壤酶活性相关性来看,根际土中,除有效态Pb与过氧化氢酶呈显著负相关外,其余重金属元素有效态与土壤酶活性相关性均没有显著相关性,而在非根际土壤中,有效态Cd与过氧化氢酶呈极显著负相关,与脲酶呈显著负相关,Zn和Cd则与土壤酶活性之间没有显著相关性。综合研究结果表明,毛竹根际土壤质量总体上明显优于非根际土,这为毛竹今后作为植物修复的材料提供了一定的理论依据。     

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.