地衣芽孢杆菌的温和性噬菌体——Ⅰ.生物学特性的研究

从25株地衣芽孢杆菌分离到7株温和性噬菌体。本文报道了这7株温和性噬菌体的噬菌斑形态、噬菌体颗粒形态、溶原菌的稳定性和免疫性以及血清学特异性。根据这些特征,7株噬菌体被分成三个类群。     

龋齿DNA疫苗(PGJAP)中污染大肠杆菌噬菌体的检测方法的建立

龋齿DNA疫苗工程菌采用的大肠杆菌DH-5α在生产过程中极易污染大肠杆菌噬菌体,所以应对原始菌种、主菌种和工作菌种及大量生产时的发酵液作大肠杆菌噬菌体检测。用大肠杆菌噬菌体VCSM13为标准噬菌体株,对大肠杆菌C3000和DH-5α分别作噬菌斑检测和pfu值计算,验证并确定以VCSM13作为标准噬菌体株,C3000作为检测菌株,对龋齿DNA疫苗原始菌种、主菌种(第一代)、工作菌种(2007001)和其发酵液(200703)分别作噬菌体检测,并建立了检测大肠杆菌噬菌体的直接噬菌斑法。结果显示VCSM13在DH-5α的噬菌斑计数为76,pfu/ml为7.6×1013,C3000的噬菌斑计数为81,pfu/ml为8.1×1013,龋齿DNA疫苗的原始菌种、主菌种、工作菌种和发酵液,噬菌斑计数全部为0。Pfu也为0。阳性对照为74,pfu/ml是7.4×1013,阴性对照为0。通过对阳性对照样本作增殖法试验及挑斑接种验证后,证明此法操作简单,灵敏度高。     

红霉素链霉菌噬菌体的分离和鉴定

我们从红霉素的异常发酵液申分离到14株红霉素链霉菌噬菌体。对每一噬菌体进行了纯化,并描述了噬菌斑的形态。大部份噬菌体的噬菌斑六而清晰透明,而P4、P8、P10的噬菌斑小而呈半透明。根据血清中和反应试验,这些噬菌体可区分为三种血清类型。选择三种血清型的代表噬临体做热失活及pFt稳定性试验,结果表明：三种类型的噬菌体对热的失活呈明显差异,而对PH的适应性较为广泛。寄主范围测定结果,P4、P9噬菌体对多种抗生素产生菌能感染,为一多价噬菌体,P1 仅对红镱紊链霉菌能感染,为单价噬菌体。     

一株粘质沙雷氏菌烈性噬菌体污水分离及特性

[目的]以粘质沙雷氏菌(8039)为宿主菌从医院污水中分离噬菌体并对其基本生物学特点进行研究.[方法]四步法污水分离噬菌体;单、双层平板噬菌斑实验筛选烈性噬菌体并观察噬菌斑形态;纯化后2%磷钨酸染色电镜观察;手工法提取噬菌体核酸酶切后琼脂糖凝胶电泳分析;利用双层平板噬菌斑实验测定最佳感染复数和完成一步生长实验.[结果]从医院污水中成功分离出粘质沙雷氏菌烈性噬菌体一株(SM701),该噬菌体有一个正多面体立体对称的头部,头径约64nm,无囊膜,有一长尾,无收缩尾鞘,尾长约143nm;基因组核酸能被双链DNA内切酶BamH Ⅰ及Hind Ⅲ切开,大小约57kb;噬菌斑圆形透明,直径1mm左右(培养12h,),边界清楚;当感染复数(multiplicity of infection,MOI)为10时,子代噬菌体滴度较高;按照一步生长实验结果绘制出一步生长曲线,可知感染宿主菌的潜伏期是约为30min,爆发期约100min,平均爆发量约为630[结论]按照国际病毒分类委员会分类标准,该噬菌体属于长尾噬菌体科(siphoviridae)烈性噬菌体,按照Bradley和Ackermann形态分类法属于B1亚群;噬菌斑与周围红色细菌生长区,颜色差异明显,非常便于观察和计数;噬菌体头部大小和形态与呼吸道病毒中的呼肠病毒和腺病毒最为接近;国内尚未见粘质沙雷氏菌噬菌体相关报道.     

大肠杆菌O157：H7中编码vt2基因的噬菌体的分离与鉴定

根据GenBank中VT1、VT2毒素的基因序列设计合成2对引物,以大肠杆菌O157:H7菌株DNA为模板,扩 增vt1、vt2。诱导只扩增出vt2的菌株释放噬菌体,利用多种指示菌经双层琼脂平板法来分离纯化VT2噬菌体,观 察噬菌斑的特征,提纯病毒粒子进行电镜观察,并对噬菌体中vt2基因检测、克隆和序列分析。结果显示VT2噬菌 体感染MC1061在双层琼脂平板上形成的噬菌斑小而混浊,多呈磨玻璃样;而首次感染大肠杆菌CC118(λpir),此 后用MC1061分离的噬菌体,再以MC1061为指示菌,在双层琼脂平板上形成小而清晰透明的噬菌斑。电镜下噬 菌体头部呈六边形外廓,尾部细长无尾鞘结构。以噬菌体DNA为模板进行PCR扩增,检测到vt2特异性DNA 带,克隆的vt2基因序列与GenBank中编码VT2毒素的核苷酸序列(X07865,NC_002655,BA000007,AF291819) 的同源性分别达到99％,确定编码VT2毒素的基因位于噬菌体上,并获得VT2噬菌体(?)HY。     

噬菌斑电子图像的计算机处理及其自动计数

噬菌斑平板计数是微生物学理论研究与实际应用中常用的方法之一.但由于平板上噬菌斑与背景反差小,而且往往出现几个噬菌斑相连,计算机识别时出现较大的误差,因此噬菌斑计数目前仍为人工方法.本文以λ噬菌体为材料,感染E.coli宿主细胞,获得噬菌斑.然后将噬菌斑制成电子图像.抽取图像中有代表性的区域,利用分水岭算法对图像进行分割处理,将相连的噬菌斑分割成单独的噬菌斑,然后利用基于区域生长法进行计数,结果与人工计数完全相同,表明我们建立的新方法可以用于噬菌斑计算机自动计数.     

噬菌斑电子图像的计算机处理及其自动计数

噬菌斑平板计数是微生物学理论研究与实际应用中常用的方法之一。但由于平板上噬菌斑与背景反差小,而且往往出现几个噬菌斑相连,计算机识别时出现较大的误差,因此噬菌斑计数目前仍为人工方法。本文以λ噬菌体为材料,感染E.coli宿主细胞,获得噬菌斑。然后将噬菌斑制成电子图像。抽取图像中有代表性的区域,利用分水岭算法对图像进行分割处理,将相连的噬菌斑分割成单独的噬菌斑,然后利用基于区域生长法进行计数,结果与人工计数完全相同,表明我们建立的新方法可以用于噬菌斑计算机自动计数。     

苏芸金杆菌六种噬菌体

从我省生产苏芸金杆菌类工厂及本所试验车间采集62号噬菌体进行了寄主范围测定,噬菌斑形状比较和电子显微镜的形态观察,可区分为六种不同的噬菌体。同时还进行了不同pH和温度处理以及紫外线照射对噬菌体存活影响的试验。可为生产上防治噬菌体的感染提供依据。     

多抗霉素链霉菌噬菌体的研究

从多抗毒素异常发酵液中分离出一种噬菌体P_sA。该噬菌体在电镜下观察呈蝌蚪形;在琼脂平板上呈圆形,边齐,透明噬菌斑。噬菌体原液在60℃、30分钟完全失活;pH4.0—9.0范围内较稳定,pH 10.0—14.0范围内仍不完全失活,pH3.0以下均失活。该噬菌体噬菌斑的形成需要Ca²⁺,仅感染多抗霉素链霉菌。对该噬菌体杀灭效果较好的消毒剂有新洁尔灭、漂白粉、甲醛、高锰酸钾、生石灰、来苏尔等。噬菌体原液在4℃冰箱保存两个月效价基本不变。     

大肠杆菌O157:H7中编码vt2基因的噬菌体的分离与鉴定

根据GenBank中VT1、VT2毒素的基因序列设计合成2对引物,以大肠杆菌O157H7菌株DNA为模板,扩增vt1、vt2.诱导只扩增出vt2的菌株释放噬菌体,利用多种指示菌经双层琼脂平板法来分离纯化VT2噬菌体,观察噬菌斑的特征,提纯病毒粒子进行电镜观察,并对噬菌体中vt2基因检测、克隆和序列分析.结果显示VT2噬菌体感染MC1061在双层琼脂平板上形成的噬菌斑小而混浊,多呈磨玻璃样;而首次感染大肠杆菌CC118(λpir),此后用MC1061分离的噬菌体,再以MC1061为指示菌,在双层琼脂平板上形成小而清晰透明的噬菌斑.电镜下噬菌体头部呈六边形外廓,尾部细长无尾鞘结构.以噬菌体DNA为模板进行PCR扩增,检测到vt2特异性DNA带,克隆的vt2基因序列与GenBank中编码VT2毒素的核苷酸序列(X07865,NC_002655,BA000007,AF291819)的同源性分别达到99%,确定编码VT2毒素的基因位于噬菌体上,并获得VT2噬菌体()HY.     

THE SIZE OF THE CELLULOSE MICROFIBRIL

Recently the lateral width of the cellulose microfibril has been estimated as 30 A rather than about 150 to 200 A, by extrapolation of data from model shadowing experiments. The difference was attributed to a layer of metal deposited during shadowing. However, direct photographs of the same microfibrils parallel and perpendicular to the direction of shadowing, of unshadowed portions of microfibrils compared with shadowed portions of the same microfibrils, of silver-stained unshadowed microfibrils, and of unshadowed, unstained segments of microfibrils give no evidence of a layer of metal of this thickness in material shadowed under normal conditions. Furthermore, the evidence for microfibril strands of about 35 A in width from negative-staining experiments is subject to a bias from the form of the filaments and from variable positive adsorption of phosphotungstic acid by cellulose. Consequently, the conclusion that the true lateral width of native cellulose microfibrils is about one-fifth of the presently accepted value is not yet justified by unequivocal direct experimental evidence.     

THE SIZE OF PORES IN COLLODION MEMBRANES

By the application of Poiseuille''s law to the rate of flow of water through collodion membranes, it is calculated that the membranes used had pore radii of the order of 0.3 to 2 x 10^–6 cm. On the same basis the number of pores per sq. cm. appears to vary from 270 x 10¹⁰ to 7 x 10¹⁰, decreasing with increase in pore size. Reasons are given for preferring these figures for the radii to figures, 100 times as large, which were calculated by others. Microscopic examination of the membranes, with dark-field illumination, indicates that they are made up of solid granules or filaments of collodion much less than 1 x 10^–4 cm. in thickness.     

MORPHOLOGICAL RATES OF ANGIOSPERM SEED SIZE EVOLUTION

The evolution of seed size among angiosperms reflects their ecological diversification in a complex fitness landscape of life‐history strategies. The lineages that have evolved seeds beyond the upper and lower boundaries that defined nonflowering seed plants since the Paleozoic are more dispersed across the angiosperm phylogeny than would be expected under a neutral model of phenotypic evolution. Morphological rates of seed size evolution estimated for 40 clades based on 17,375 species ranged from 0.001 (Garryales) to 0.207 (Malvales). Comparative phylogenetic analysis indicated that morphological rates are not associated with the clade's seed size but are negatively correlated with the clade's position in the overall distribution of angiosperm seed sizes; clades with seed sizes closer to the angiosperm mean had significantly higher morphological rates than clades with extremely small or extremely large seeds. Likewise, per‐clade taxonomic diversification rates are not associated with the seed size of the clade but with where the clade falls within the angiosperm seed size distribution. These results suggest that evolutionary rates (morphological and taxonomic) are elevated in densely occupied regions of the seed morphospace relative to lineages whose ecophenotypic innovations have moved them toward the edges.