Tailed bacteriophages: the order caudovirales.
Tailed bacteriophages: the order caudovirales.
复制标题
DOI：
10.1016/s0065-3527(08)60785-x
复制
发表时间：
1998-01-01
影响因子：
--
通讯作者：
Ackermann, H W
中科院分区：
文献类型：
--
作者：
Ackermann, H W
尾状噬菌体有一个共同的起源，构成了一个有三个科的目，命名为尾状噬菌体。它们结构化的尾巴是独一无二的。尾状噬菌体具有一系列高级分类特性，并表现出许多在病毒中独特或罕见的兼性特征，例如尾部附属物和不寻常的碱基。它们与其他病毒，特别是疱疹病毒，具有归因于趋同进化的形态发生和生活方式要素。尾状噬菌体有三种溶原性，如噬菌体lambda、Mu和P1。溶原性表现为通过水平基因转移获得的次要特性。氨基酸序列比对（特别是DNA聚合酶、整合酶和肽聚糖水解酶）表明，尾状噬菌体中经常发生水平基因转移。常见的衣壳蛋白和尾部蛋白尚未检测到。尾状噬菌体可能是从带有少量基因的小蛋白壳进化而来的，这些基因足以满足一些基础水平的生产性感染。这个早期阶段已经无法追溯了。在某一时刻，这个前体噬菌体变得完美。它的一些特征非常完美，一直流传到今天。用过去时列出尾状噬菌体现今的主要特性，以构建这些病毒的初步历史是很有诱惑力的：尾噬菌体起源于前寒武纪早期，远早于真核生物及其病毒。2. 无尾噬菌体已经是一种相当进化的病毒，它有一个直径约60纳米的二十面体头和一个长而不可收缩的六重对称尾巴。衣壳包含约50 kb的单分子dsDNA，尾部可能有固定装置。头和尾由一个接头连接在一起。a.该颗粒不含脂质，比后来的大多数病毒都重，DNA含量与其衣壳大小成正比（约50%）。b.它的大部分DNA编码结构蛋白。形态形成基因聚集在基因组的一端，头部基因先于尾部基因。裂解酶可能被编码为。噬菌体基因组的一部分是不必要的，可能是细菌。尾噬菌体从一开始就是通用的转导剂吗？3. 病毒从外部注入宿主的DNA，感染宿主。复制涉及数波转录和DNA串联体的形成。新的噬菌体是在被肽聚糖水解酶（和holin）裂解宿主膜后被感染的细胞爆发而释放出来的。衣壳从连接点和支架周围组装起来。它们经历了一个复杂的成熟过程，包括蛋白质裂解和衣壳扩张。正面和反面分别组装，然后再连接。b. DNA被切成大小，并通过头部机制进入预先制成的衣壳。4. 随后，有尾噬菌体的多样化表现为：a.进化出可收缩的或短的尾巴和细长的头。b.与其他噬菌体交换基因或基因片段。通过获得整合酶-切除酶复合物、质粒部分或转座子而变得温和。d.获取DNA和RNA聚合酶及其他复制酶。e.与宿主交换溶酶基因。f.由于获得转座子（Mu）或蛋白质引发的DNA聚合酶（phi 29）而丧失形成串联体的能力。今天的尾噬菌体表现为嵌合体，但它们的单系起源仍然铭刻在它们的形态、基因组结构和复制策略中。这在衣壳蛋白和尾部蛋白的三维结构中也很明显。它不太可能在氨基酸序列中被发现，因为构成蛋白一定是如此古老，以至于关系被抹去，大多数或所有与复制、溶原和裂解相关的蛋白质似乎都是借来的。然而，尾噬菌体的特性和行为的总和是如此独特，以至于尾噬菌体不能与其他病毒混淆。
Tailed bacteriophages have a common origin and constitute an order with three families, named Caudovirales. Their structured tail is unique. Tailed phages share a series of high-level taxonomic properties and show many facultative features that are unique or rare in viruses, for example, tail appendages and unusual bases. They share with other viruses, especially herpesviruses, elements of morphogenesis and life-style that are attributed to convergent evolution. Tailed phages present three types of lysogeny, exemplified by phages lambda, Mu, and P1. Lysogeny appears as a secondary property acquired by horizontal gene transfer. Amino acid sequence alignments (notably of DNA polymerases, integrases, and peptidoglycan hydrolases) indicate frequent events of horizontal gene transfer in tailed phages. Common capsid and tail proteins have not been detected. Tailed phages possibly evolved from small protein shells with a few genes sufficient for some basal level of productive infection. This early stage can no longer be traced. At one point, this precursor phage became perfected. Some of its features were perfect enough to be transmitted until today. It is tempting to list major present-day properties of tailed phages in the past tense to construct a tentative history of these viruses: 1. Tailed phages originated in the early Precambrian, long before eukaryotes and their viruses. 2. The ur-tailed phage, already a quite evolved virus, had an icosahedral head of about 60 nm in diameter and a long non-contractile tail with sixfold symmetry. The capsid contained a single molecule of dsDNA of about 50 kb, and the tail was probably provided with a fixation apparatus. Head and tail were held together by a connector. a. The particle contained no lipids, was heavier than most viruses to come, and had a high DNA content proportional to its capsid size (about 50%). b. Most of its DNA coded for structural proteins. Morphopoietic genes clustered at one end of the genome, with head genes preceding tail genes. Lytic enzymes were probably coded for. A part of the phage genome was nonessential and possibly bacterial. Were tailed phages general transductants since the beginning? 3. The virus infected its host from the outside, injecting its DNA. Replication involved transcription in several waves and formation of DNA concatemers. Novel phages were released by burst of the infected cell after lysis of host membranes by a peptidoglycan hydrolase (and a holin?). a. Capsids were assembled from a starting point, the connector, and around a scaffold. They underwent an elaborate maturation process involving protein cleavage and capsid expansion. Heads and tails were assembled separately and joined later. b. The DNA was cut to size and entered preformed capsids by a headful mechanism. 4. Subsequently, tailed phages diversified by: a. Evolving contractile or short tails and elongated heads. b. Exchanging genes or gene fragments with other phages. c. Becoming temperate by acquiring an integrase-excisionase complex, plasmid parts, or transposons. d. Acquiring DNA and RNA polymerases and other replication enzymes. e. Exchanging lysin genes with their hosts. f. Losing the ability to form concatemers as a consequence of acquiring transposons (Mu) or proteinprimed DNA polymerases (phi 29). Present-day tailed phages appear as chimeras, but their monophyletic origin is still inscribed in their morphology, genome structure, and replication strategy. It may also be evident in the three-dimensional structure of capsid and tail proteins. It is unlikely to be found in amino acid sequences because constitutive proteins must be so old that relationships were obliterated and most or all replication-, lysogeny-, and lysis-related proteins appear to have been borrowed. However, the sum of tailed phage properties and behavior is so characteristic that tailed phages cannot be confused with other viruses.