高产铁载体棉田土壤细菌SS05的筛选与鉴定

【目的】研究从棉田土壤中筛选得到的高产铁载体细菌产铁载体能力、分类地位和抑菌活性。【方法】通过改良蔗糖-天冬氨酸培养基选择性筛选产铁载体细菌,通过分光光度计法测定铁载体活性,通过混菌法测定产铁载体细菌上清液对棉花枯萎病致病菌尖孢镰刀菌(Fusarium oxysporum)的抑菌效果,采用形态学、生理生化鉴定及16S rDNA序列系统发育分析对高产铁载体菌株进行鉴定。【结果】从棉田土壤中筛选到162株产铁载体细菌,30株产铁载体能力较强的细菌中21株具有较高产铁载体能力,菌株SS05的铁载体活性单位达到98.3%;在低铁条件下,SS05上清液对F.oxysporum具有显著的抑制作用;SS05与莫哈韦芽孢杆菌(Bacillus mojavensis)最为接近。【结论】SS05是高产铁载体菌株,与莫哈韦芽孢杆菌(Bacillus mojavensis)最为接近,在低铁培养条件下其上清液对F.oxysporum具有显著的抑制作用。     

棉花黄萎病拮抗细菌产铁载体测定及其对抑菌活性的影响

【背景】棉花是新疆农业的支柱产业,棉花黄萎病严重影响棉花产量和纤维品质,有效的防治途径是目前解决的首要任务。【目的】探究BacillusvelezensisBHZ-29、Bacillusatrophaeus SHZ-24、Bacillus subtilis SHT-15、Bacillus vanillea SMT-24菌株产铁载体能力及其对抑菌活性的影响。【方法】MKB-CAS双层平板检测铁载体,Arnow法与高氯酸铁法鉴定铁载体类型,CAS染液定量铁载体,琼脂扩散法测定低铁条件下铁载体对抑菌物质的影响。【结果】MKB-CAS固体平板菌体周围出现橙紫色显色反应,Arnow实验4株拮抗菌反应液颜色为红色,高氯酸铁实验反应液颜色为黄色;BHZ-29、SHZ-24、SHT-15、SMT-24菌株铁载体定量活性单位最大值分别为8.27%±0.61%、31.80%±2.06%、16.06%±3.61%、15.53%±0.51%,吸光度值As/Ar比值最小分别为0.917±0.092、0.682±0.021、0.845±0.005、0.846±0.008。BHZ-29、SHZ-24、SMT-24菌株含铁离子浓度0、10、20μmol/L 3组处理发酵无菌滤液均未出现抑菌圈,SHT-15菌株3组处理出现抑菌圈,抑菌圈直径大小无差异性。【结论】4株拮抗菌株均产铁载体,铁载体类型为儿茶酚型,4株拮抗菌株整体产铁载体能力较低,最高达31.80%±2.06%,产铁能力As/Ar比值高于0.682时,BHZ-29、SHZ-24、SMT-24菌株含铁离子浓度0、10、20μmol/L 3组处理发酵无菌滤液对抑菌活性无影响,SHT-15菌株3组不同铁离子浓度处理对抑菌物质影响差异不显著。     

落地生根内生固氮菌多样性和促生特性

【背景】内生固氮菌可以定殖于植物体内为植物提供营养物质,还能通过代谢促进植物生长,目前对于落地生根内生菌的研究鲜见报道。【目的】研究落地生根中内生固氮菌多样性。【方法】从表面消毒的植物组织中分离纯化内生菌,并通过乙炔还原法测定菌株的固氮酶活性。采用SDS-PAGE全细胞蛋白电泳和IS指纹图谱对菌株聚类,各类群代表菌株进行16S rRNA基因系统发育分析和生理生化鉴定。测定菌株固氮、分泌生长素和ACC脱氨酶、产铁载体、溶磷和解钾等促生特性。【结果】从落地生根中分离纯化出26株内生固氮菌,聚为5个类群,隶属于4个属的5个菌种,且各类群代表菌株具有多种促生功能。【结论】从落地生根中分离获得的内生菌具有丰富的遗传多样性和促生特性,并且存在新的微生物资源,有待开发利用。     

4株茶树根际促生菌菌株的鉴定及促生作用

【背景】根际促生菌可以促进植物生长、提高植物抗性。茶树根际具有特殊的根土微生物生境,可以获得具促生作用的有益微生物。【目的】探究4株茶树根际促生菌菌株的分类地位及促生作用,筛选优良的根际促生菌菌株。【方法】通过形态、生理生化特征、16S rRNA基因序列同源性比对鉴定4株茶树根际促生菌,采用钼锑抗比色法测定溶磷量,通过比色法测定ACC脱氨酶活性、CAS法测定产铁载体能力、Salkowski法测定产IAA (Indoleacetic acid)的能力进行促生作用研究,通过盆栽实验测试白菜、空心菜、苋菜及水稻的株高及鲜重以分析促生效应。【结果】鉴定KKS-6-N1为放射型土壤杆菌(Agrobacteriumradiobacter), KKS-7-N7为铜绿假单胞菌(Pseudomonas aeruginosa),GD3为Pseudomonashunanensis,GD12为弯曲芽孢杆菌(Bacillusflexus)。固氮菌株KKS-6-N1可产铁载体;固氮菌株KKS-7-N7具有解磷及产铁载体能力,分泌的IAA含量高达101.29mg/L;解钾菌株GD3具溶磷能力,分泌的ACC脱氨酶酶活为8.09μmol/(mg·h),相对铁载体含量为0.31;具固氮解钾性能的菌株GD12分泌的ACC脱氨酶活性为14.46μmol/(mg·h)。盆栽试验表明,4个菌株对白菜、空心菜、苋菜的株高和鲜重均有明显促进作用,尤以GD3效果更甚。【结论】茶树根际促生菌菌株Pseudomonas hunanensis GD3促生作用显著,具有开发成微生物菌肥的潜力。     

可产生铁载体的春兰根内生细菌多样性

摘要：【目的】了解可产生铁载体的春兰根内生细菌的多样性,以便筛选到高效的植物促生细菌。【方法】采用CAS检测法测定了189株春兰根内生细菌产生铁载体的能力,并结合16S rRNA基因系统发育分析对可产铁载体的春兰根内生细菌多样性进行了研究。【结果】从189株春兰内生细菌中筛选到47株可产生铁载体的细菌,占菌株总数的24.9%。16S rRNA基因系统发育分析结果表明,47株细菌分属于4个系统发育类群（Alphaproteobacteria,Betaproteobacteria,Firmicutes,Actinobacteria）,17个属的31个种。其中放线菌门为最优势类群（42.6%）,芽孢杆菌属（Bacillus）和贪噬菌属（Variovorax）为优势菌属,且贪噬菌属为高产铁载体的主体菌属。另外有2个菌株可能代表两个不同属的新物种。【结论】春兰根中可产生铁载体的内生细菌具有丰富的多样性。     

百合枯萎病拮抗细菌的筛选、鉴定及其抑菌物质研究

【目的】筛选对百合枯萎病具有抑菌活性的拮抗细菌,对其抑菌活性物质进行初步分离纯化分析。【方法】以强致病力的百合尖孢镰刀菌(Fusarium oxysporum)为靶菌,采用系列稀释法和平板对峙法初筛拮抗细菌,并通过产铁载体能力、水解酶活性、土壤定殖力等多种生防特性指标进行复筛,结合形态学特征、生理生化指标和16S rRNA基因序列比对鉴定其分类地位;利用百合尖孢镰刀菌作为靶菌进行活性追踪,结合酸沉淀、快速柱色谱、HPLC等分离纯化手段,对菌发酵液中的抑菌活性物质进行纯化分析。【结果】在64株百合根际细菌和386株海洋细菌中进行初筛,得到9株对百合镰刀菌具有较强拮抗活性的菌株,最后筛选了1株拮抗活性较强且产铁载体能力和水解酶活性、土壤定殖能力较高的菌株11B91,鉴定为解淀粉芽孢杆菌(Bacillus amyloliquefaciens),其抑菌活性物质初步推测可能为iturin和fengycin脂肽类化合物。【结论】菌株11B91在百合枯萎病的生物防治中具有潜在的应用价值,证实海洋来源的微生物也具有防治陆地植物病原菌的潜力,为植物病害的防治拓宽了思路。     

一株人参内生1-氨基环丙烷-1-1羧酸(ACC)脱氨酶活性细菌的筛选、鉴定及其对宿主生长的影响

【目的】从人参内生细菌中获得具有1-氨基环丙烷1-羧酸(ACC)脱氨酶活性的菌株,并进行促生效果的验证。【方法】结合初筛和复筛的方法筛选具有ACC脱氨酶活性的人参内生菌株;采用Ashby培养基和固氮酶基因验证其固氮潜能;菌碟法及钼锑抗比色法测定其解磷能力;CAS方法检测产生铁载体能力;通过室内及田间试验测定菌株对人参生长的促进作用。通过形态学、生理生化测定及16S rRNA序列分析明确菌株的分类地位。【结果】从120株人参内生菌中获得了一株具有较高ACC脱氨酶活性的菌株JJ8-3,其酶活性为α-酮丁酸6.7μmol/(mg·h);且具有解磷特性、固氮潜能和产生铁载体能力;能明显促进人参种子及根部的生长;经鉴定菌株JJ8-3为荧光假单胞菌(Pseudomonas fluorescens)。【结论】获得了一株具有ACC脱氨酶活性的人参内生细菌,将为其在促进植物生长中的应用和研究奠定基础。     

假想的脂蛋白连接酶对肺炎链球菌毒力的影响

【目的】探索假想脂蛋白连接酶(putative lipoate-protein ligase,LPL)对肺炎链球菌毒力的影响。【方法】采用长臂同源多聚酶链式反应(LFH-PCR)的方法失活lpl基因,通过PCR、测序鉴定缺陷菌株,采用细胞实验比较缺陷菌和野生菌对宿主细胞的粘附能力,并通过动物实验观察lpl基因缺陷后菌株毒力的变化。【结果】小鼠毒力实验表明野生菌株和缺陷株半数致死时间均为12h,两者比较无统计学差异;缺陷菌在对宿主细胞的粘附能力明显高于野生菌株(P0.01);体外荚膜染色实验表明,野生菌和缺陷菌均有荚膜。【结论】实验结果提示lpl基因对细菌粘附宿主细胞有抑制作用,但不影响其腹腔感染小鼠的能力。     

具有拮抗空肠弯曲杆菌能力鸡源乳酸菌的筛选及特性

【目的】从鸡粪中筛选具有拮抗空肠弯曲杆菌能力的乳酸菌,研究其肠道益生特性,探讨其对空肠弯曲杆菌鞭毛毒力因子的影响。【方法】利用牛津杯法测定40株鸡粪源乳酸菌菌株的抑菌活性以确定抑菌性能好的菌株,利用16S r RNA基因分析进行菌株鉴定,采用HT-29细胞测定菌株的细胞粘附能力,通过模拟胃肠液实验分析菌株对胃肠道环境的耐受性,利用扫描电镜分析乳酸菌无细胞提取物对空肠弯曲杆菌鞭毛毒力因子的影响。【结果】从鸡粪中分离得到40株菌株,进一步筛选得到X13、X14和G20等3株拮抗空肠弯曲杆菌能力较强的菌株,经16S r RNA基因序列分析分别鉴定为罗伊氏乳杆菌、唾液乳杆菌和鸡乳杆菌;HT-29细胞粘附实验表明X13、X14及G20的粘附指数分别为11.5、20.3和14.3个/细胞,均具有良好的粘附能力;3株乳酸菌对人工胃肠液均具有良好的耐受性;扫描电镜观察表明,与对照组相比,3株纯培养乳酸菌无细胞提取物均能抑制空肠弯曲杆菌鞭毛毒力因子的合成。【结论】从鸡粪中筛选得到了3株能有效抑制空肠弯曲杆菌生长并能抑制其鞭毛合成的乳酸菌,有望作为拮抗性饲用益生菌用于控制禽畜的空肠弯曲杆菌感染。     

黑麦草根际产铁载体细菌HMGY6B的筛选鉴定及对病原菌的拮抗作用

【目的】从石灰性土壤中分离筛选出铁载体合成能力强、抗病效果好的菌株。【方法】采用刃天青(Chrome azural S,CAS)平板检测法,定性、定量筛选产铁载体能力较强的菌株,通过菌株形态、生理生化特征、16S r RNA基因序列相似性和系统发育分析,鉴定细菌类型,然后采用平板对峙法研究菌株与病原菌的拮抗作用。【结果】从多年生黑麦草根际土壤中分离得到一株产铁载体能力很强的菌株HMGY6B,经鉴定,该菌属假单胞菌属Pseudomonas菌株,其产生的儿茶酚型铁载体对黄瓜灰霉病(Botrytis cinerea)有显著的拮抗作用,在低铁条件下(0.16、2、5、10μmol/L FeCl_3)对黄瓜灰霉病的生长抑制率高达91.2%,但在富铁条件下(50μmol/L FeCl_3)降为30.2%,100μmol/L FeCl_3抑制率仅为5.5%。【结论】菌株HMGY6B可用于今后复合型抗病生物菌肥的开发研制。     

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.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

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.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细