Tectiviridae. Tectiviridae

Description of Tectiviridae adapted from ICTVdb Virion Properties Morphology Virions consist of a capsid and an internal lipid membrane. Virus capsid is not enveloped. Virions are tail-less, but can produce tail-like tubes; upon adsorption, or after chloroform treatment. Capsid/nucleocapsid is round and exhibits icosahedral symmetry. The isometric capsid has a diameter of 63 nm. The capsid shells of virions are composed of two layers. The outer capsid consists of a smooth, rigid 3 nm thin protein shell and appear to have a hexagonal in outline. Surface projections are distinct 20 nm long spikes protruding from each apex, or lost during preparation. Inner capsids consist of a 5-6 nm flexible shell made from a thick lipoprotein vesicle. The genome forms a tightly packed coil. Physicochemical and Physical Properties Virions have a buoyant density in CsCl of 1.29 g cm-3. Nucleic Acid The Mr of the genome constitutes 14-15% of the virion by weight. The genome is not segmented and contains a single molecule of linear double-stranded DNA. The complete genome is 147000-157000 nucleotides long. Proteins The viral genome encodes structural proteins. Lipids Lipids are present and located in the inner vesicle (constitute 60%). Virions are composed of 15% lipids by weight. The composition of viral lipids and host cell membranes are identical. The lipids are host derived. Lipids in the viral membrane have a bilayer structure (and seem to be in a liquid crystalline phase). Viral membranes include 56 % phosphatidyl ethanolamine and phosphatidyl glycerol (37 %; they are higher than in the host, but vary according to the host strain)

囊状噬菌体科（Tectiviridae）描述（改编自国际病毒分类委员会数据库（ICTVdb））

## 病毒粒子特性
### 形态学
病毒粒子由衣壳（capsid）与内部脂质膜组成。该病毒衣壳无包膜（enveloped）。病毒粒子无尾，但在吸附宿主或经氯仿处理后可形成尾状管结构。衣壳/核衣壳呈球形，具有二十面体对称（icosahedral symmetry）。等轴衣壳直径为63 nm。病毒粒子的衣壳壳层分为两层：外层衣壳为光滑、坚硬的3 nm厚蛋白质外壳，外观呈六边形轮廓；表面存在独特的20 nm长棘突，从每个顶点伸出，或在样品制备过程中丢失。内层衣壳为5-6 nm厚的柔性壳层，由厚脂蛋白囊泡构成。病毒基因组呈紧密盘绕的结构。

### 物理化学与物理特性
病毒粒子在氯化铯（CsCl）中的浮力密度为1.29 g·cm⁻³。

#### 核酸
病毒基因组的相对分子质量占病毒粒子总重量的14%-15%。基因组不分节段，为单分子线性双链DNA（double-stranded DNA）。完整基因组长度为147000-157000核苷酸。

#### 蛋白质
病毒基因组编码结构蛋白。

#### 脂质
脂质存在于内层囊泡中（占比60%）。病毒粒子的总脂质含量为其总重量的15%。病毒脂质的组成与宿主细胞膜完全一致，且脂质来源于宿主。病毒膜内的脂质呈双层结构（且似乎处于液晶相）。病毒膜中含有56%的磷脂酰乙醇胺与37%的磷脂酰甘油，该比例高于宿主细胞膜，且会随宿主菌株的不同而发生变化。