绞股蓝内生真菌抗大肠杆菌抗菌机制的研究

【目的】药用植物内生真菌是一种新型抗生素的微生物资源,研究绞股蓝内生真菌JY25的抗菌机制对内生真菌的研发具有重要意义。【方法】以二倍稀释法测定发酵液的最小抑菌浓度(MIC)和最小杀菌浓度(MBC);以MIC测定发酵液对大肠杆菌生长的抑制作用;扫描电镜观察发酵液作用下的大肠杆菌形态变化;同时,以β-半乳糖酶、碱性磷酸酶和电导率测定发酵液对细胞膜和细胞壁的损伤效果;采用考马斯亮蓝法检测发酵液对蛋白质合成的影响。【结果】JY25发酵液对大肠杆菌MIC为7 g/L、MBC为14 g/L;MIC浓度的发酵液使细菌对数生长期延迟12 h,菌体形态发生严重的畸形和破损;随着抑菌作用时间的延长,β-半乳糖酶含量增加、电导率增加,同时,实验发现大肠杆菌蛋白质合成异常,未检测到碱性磷酸酶。【结论】绞股蓝内生真菌JY25主要以破坏细菌的细胞膜及影响细菌蛋白质合成而抑制细菌生长。     

海洋芽孢杆菌（Bacillus marinus）B-9987菌株抑制病原真菌机理的研究

摘要：【目的】：探讨海洋芽孢杆菌（Bacillus marinus）B-9987菌株的代谢产物BMME-1,对植物病原真菌茄链格孢菌的抑菌作用机理。【方法】分别使用分光光法、气相色谱-质谱GC-MS联用技术、红外光谱法等,检测了BMME-1处理病原真菌后,菌体渗透性、细胞壁及细胞膜成份的变化。【结果】BMME-1对茄链格孢菌的抑菌中浓度（MIC50）为6.2 mg/L,最小杀菌浓度（MFC）为50 mg/L,在MIC50浓度或高于此浓度处理靶标菌,将导致菌体蛋白质、核酸等大分子物质的外流;处理菌株葡聚糖结     

水稻细菌性条斑病菌中分泌蛋白质组表达谱的研究

水稻细菌性条斑病菌(Xamthomonas.oryzae pv.oryzicola,Xoc)是水稻的主要病原菌之一,其引发的水稻细菌性条斑病可造成水稻严重减产。本研究以Xoc GX01作为实验菌株,通过细菌培养、分泌蛋白提取、纯化获得总分泌蛋白,将样品酶解后通过LC-MS/MS技术鉴定了分泌蛋白质表达谱,共鉴定蛋白质661个,同时利用生物信息学技术对鉴定蛋白进行基因本体(gene ontology,GO)生物学分类,对生物功能、生物进程以及细胞组件进行了说明。为阐明植物病原菌的作用机理以及植物-病原细菌互作提供了理论基础。     

秦皮素对大肠埃希菌作用机制的初步研究

目的以大肠埃希菌ATCC 25922为供试菌,探讨秦皮素的抑菌活性及其作用机制。方法利用TTC法测定秦皮素对大肠埃希菌ATCC 25922的最低抑菌浓度;通过测定加药前后菌体培养液电导率和大分子的变化及观察扫描电镜和透射电镜电镜结果,分析秦皮素对其细胞膜的影响;通过SDS-PAGE测定秦皮素对供试菌株蛋白含量的影响;采用逐个检出法研究秦皮素对大肠埃希菌ATCC 25922质粒合成的抑制作用。结果秦皮素可抑制大肠埃希菌ATCC 25922的生长,其最低抑菌浓度为40μg/mL。秦皮素作用菌体5 h后,培养液中的电导率比对照组增加1.96%,但DNA和RNA大分子增加的不明显。秦皮素作用大肠埃希菌20 h后,菌体可溶性蛋白总量比对照组降低42%。秦皮素对大肠埃希菌的质粒有消除作用,药物作用48 h后,秦皮素对大肠埃希菌的质粒消除率为60.3%。结论秦皮素可抑制大肠埃希菌的生长,其抑菌作用机制与抑制菌体内蛋白质合成和消除菌体内的质粒有关,但对大肠埃希菌细胞膜的影响不大。     

基于LC-MS-MS技术建立水稻细菌性条斑病菌的蛋白质表达谱的研究

水稻细菌性条斑病菌(Xamthomonas.oryzae pv.oryzicola,Xoc)是水稻的主要病原菌之一,其引发的水稻细菌性条斑病可造成水稻严重减产。本文利用Xoc GX01作为实验菌株,通过细菌培养、蛋白提取、纯化获得总蛋白,利用高p H值C18反相色谱作为第一维分离方式,再将收集的馏分通过LC-MS/MS技术得到了总蛋白质表达谱,共鉴定蛋白质1 621个,同时利用生物信息学技术对鉴定蛋白进行基因本体(gene ontology,GO)生物学分类,对生物功能、生物进程以及细胞组件进行了注释。为明确植物病原菌的作用机理和研究植物-病原微生物互作提供了方法学基础。     

Plantaricin 163对热杀索丝菌的抗菌活性及其作用机制

【背景】热杀索丝菌(Brochothrix thermosphacta)为鲫鱼在4°C贮藏过程中的主要腐败菌,Plantaricin 163是由植物乳杆菌产生的一种新型广谱细菌素,能明显延长鲫鱼的贮藏期。【目的】研究Plantaricin163对热杀索丝菌的抗菌活性和作用机制。【方法】通过测定最小抑菌浓度(Minimuminhibitoryconcentration)和杀菌动力学了解Plantaricin163对热杀索丝菌的抗菌效果,并从电导率的变化、核酸和蛋白的泄露、流式细胞实验、扫描电镜和透射电镜观察等4个方面探讨Plantaricin 163对热杀索丝菌的作用机制。【结果】Plantaricin 163对热杀索丝菌的的最小抑菌浓度为32μg/mL,优于Nisin的作用效果,作用方式为杀菌模式,6 h内能完全杀死热杀索丝菌。Plantaricin163能够通过增加热杀索丝菌细胞膜的通透性,增加胞外电导率,进而破坏细胞膜完整性,导致内容物泄漏,并影响细胞的外部形态和内部结构,从而导致菌体细胞瓦解死亡。【结论】Plantaricin 163可以破坏热杀索丝菌的细胞膜和内部结构,发挥抗菌活性。     

一株拮抗黄单胞菌的贝莱斯芽孢杆菌的分离和鉴定

【目的】为了筛选防治水稻条斑病(bacterial leaf streak,BLS)的生防细菌。【方法】以水稻条斑病菌(Xanthomonas oryzae pv. oryzicola,Xoc)的模式菌株RS105为靶标菌,采用平板稀释和抑菌圈法,从空心菜根际土壤中筛选到一株对RS105具有拮抗作用的细菌菌株504。通过形态学、生理生化特征以及16SrDNA和gyrA序列分析对菌株504进行了鉴定。利用牛津杯法测定504对植物病原黄单胞菌的拮抗活性及其无菌发酵液拮抗活性的稳定性。通过PCR扩增预测504编码合成脂肽类和聚酮类化合物的合成相关基因。采用苗期水稻注射接菌法来评价水稻组织中504对Xoc的拮抗活性。【结果】菌株鉴定结果表明504为贝莱斯芽孢杆菌,命名为Bacillusvelezensis504。抑菌实验显示,B.velezensis504对黄单胞菌属的细菌具有较好的抑菌活性,对水稻白叶枯病菌(X. oryzae pv. oryzae,Xoo)的拮抗效果最显著。基因预测结果显示,B. velezensis 504含有fenA、dhbA、sfrA、bmyA、beaS、dfnA及bacA等编码脂肽类和聚酮糖类抑菌化合物的基因簇。其无菌发酵液的活性物质耐高温和蛋白酶降解,但不耐强酸、强碱,在pH值为5.5–8.9时仍具有稳定的拮抗活性。在高感水稻品种原丰早上,B. velezensis 504对Xoc在水稻叶片中引起的水渍症状具有显著的抑制作用。【结论】B. velezensis 504能够特异性拮抗黄单胞菌,在黄单胞菌引起的细菌性病害的生物防治中将具有较大的应用潜力。     

草珊瑚炭疽病拮抗细菌的鉴定及其抑菌机理

【背景】草珊瑚炭疽病发生严重,目前尚未有植物内生细菌对该病原菌生物防治的研究报道。【目的】筛选对肿节风炭疽病Colletotrichumdematium具有拮抗作用的内生细菌,并对其抑菌机理进行研究。【方法】采用平板稀释法从广西不同地区采集健康肿节风植株的不同组织分离、纯化获得内生细菌。【结果】平板对峙试验结果表明,来自茎的RJ-4和JJ-5对草珊瑚炭疽病具有较强的拮抗作用,其中拮抗作用最强的菌株是RJ-4,其抑制率达到84.10%。抗菌谱测定结果表明,RJ-4、JJ-5对供试的14种病原真菌均有明显的拮抗效果,拮抗作用最强的是RJ-4,平均抑制率达到95.30%;抑菌机理研究结果表明,该菌株可以分泌蛋白酶和纤维素酶以及几丁质酶,破坏病菌菌丝,抑制病菌生长;含有拮抗细菌的发酵液对病原菌菌丝抑制明显,菌丝扭曲、断裂且分枝缠绕、菌丝颜色加深等。通过形态学特性和16S rRNA基因鉴定,RJ-4菌株为解淀粉芽孢杆菌(Bacillus amyloliquefaciens)。【结论】RJ-4菌株具有抑菌抗病功能,并能产生多种抗菌活性物质,这可为新型抗菌物质提供资源。     

外源化学物质对副溶血性弧菌药物敏感性的影响

【目的】细菌对抗生素的耐药性已成为全球公共卫生问题关注的热点。有研究表明外源添加化学物质可以增强耐药细菌对抗生素的敏感性。本研究比较了3种化学物质葡萄糖、丙氨酸、甘油对增强副溶血性弧菌抗生素敏感性的作用效果。【方法】在亚抑菌浓度抗生素胁迫条件下,通过比较副溶血性弧菌在添加终浓度为10 mmol/L葡萄糖、丙氨酸、甘油后细菌存活率随时间的变化水平,来观察弧菌对亚抑菌浓度抗生素敏感性作用效果的改变,并采用氧化磷酸化解偶联剂CCCP对实验结果进行验证。【结果】发现3种外源化学物质均能增强亚抑菌浓度氨基糖苷类抗生素对副溶血性弧菌的杀菌能力,其中外源添加葡萄糖对增强亚抑菌浓度卡那霉素的杀菌能力最为显著,而对其他种类抗生素的杀菌能力则无明显增强作用。加入氧化磷酸化解偶联剂CCCP后可消除由外源化学物质引发的弧菌抗生素敏感性作用增强的现象。【结论】通过调节细菌细胞代谢水平可提高耐药副溶血性弧菌对氨基糖苷类抗生素的敏感性,对多重耐药副溶血性弧菌的防控具有一定的实际应用价值。     

大蒜浸出液对平菇细菌性褐斑病病原菌托拉斯假单胞杆菌的抑菌作用

【背景】由托拉斯假单胞杆菌(Pseudomonas tolaasii)引起的平菇细菌性褐斑病在国内外大面积发生,导致产量降低,并有潜在的安全风险,寻找安全有效的抑菌剂对产业发展具有重要意义。【目的】通过5种不同溶剂提取得到大蒜浸出液,测定其对平菇细菌性褐斑病病原菌托拉斯假单胞杆菌的抑制作用,同时检测其对平菇菌丝生长的作用。【方法】利用抑菌圈法测定5种不同的大蒜浸出液对托拉斯假单胞杆菌的抑菌作用,利用平板扩散法筛选能促进平菇菌丝生长的药剂及适宜的浓度。【结果】5种大蒜浸出液原液对托拉斯假单胞杆菌均有显著的抑菌活性,其中大蒜山杏壳木醋液浸出原液抑菌效果最强。不同浓度的大蒜浸出液抑菌作用比较发现,浓度为10%的大蒜山杏壳木醋液浸出液具有较好的抑菌效果,其抑菌效果与0.33 mg/mL的链霉素相当,并对平菇菌丝生长有显著的促进作用,菌丝生长速度显著大于对照,并且菌丝浓密,边缘整齐。【结论】本研究为大蒜与山杏壳木醋液复配药剂防治平菇细菌性褐斑病奠定了实验基础。     

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.