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你可能喜欢λ噬菌体_百度百科
关闭特色百科用户权威合作手机百科 收藏 查看&λ噬菌体本词条缺少名片图，补充相关内容使词条更完整，还能快速升级，赶紧来吧！
1951年J. Lederberg的妻子Esther Lederberg证明了J. Lederberg和Tatum用来杂交的K12中有原，并命名为λ，经10年的研究搞清了溶原化的实质。发现者Esther Lederberg领&&&&域生物学
在E.coli K12中是有的存在。Jacob和Wollman（1956年）发现了（zygotic induction）现象，并利用确定了几个E.coli染色体上的整合位点。他们发现Hfr（λ）×F－所得到的频率要比Hfr×F－（λ）或Hfr（λ）×F－（λ）要低得多。这是由于在Hfr（λ）×F－的杂交中，原噬菌体进入无的受体中，进行大量复制使受体细胞裂解（图8-20b），因此不易得到重组子，此现象就称为。现在我们再回过头来查阅一下传递等级作图，实验以及都是采用Hfr×F－（λ）就是不致产生合子诱导的缘故。λ噬菌体是长尾噬菌体科的一种温和噬菌体。λ噬菌体是双链DNA噬菌体，有直径55nm的二十面体头部，末端有细长尾丝的非收缩尾。DNA是线性分子，有粘性末端即单链延伸12个核苷酸，故感染后线性基因组可立即环化。[1]
λ DNA有一个噬菌体结合位点，可与细菌结合位点形成碱基配对，细菌结合位点位于大肠杆菌染色体上半乳糖或gal操纵子和生物素操纵子之间。两个位点配对后，整合酶在一种特异宿主蛋白的辅助下催化病毒和细菌DNA链和物理交换，环状λ DNA以线性整合进大肠杆菌DNA上毗邻gal操纵子的位置，称之为前噬菌体。[1]
λ噬菌体的长达50 Kb，共61个基因，其中38个较为重要。其生活史如图8-15所示，可分为和周期。细菌处于状态时，细胞质中有一些λ CI的产物CI蛋白（见第十八章）,这是一种，可以阻止λ左、右两个早期起动子的转录，使之不能产生一些复制及细胞裂解的蛋白。λ的DNA随着的染色体复制而复制。但在UV诱导下Rec蛋白可降解CI蛋白（见第17章），诱导90%的细胞裂解。有时λ也可自发地（10-5）从的染色体上游离出来，进行复制，最终导致的裂解，此称为治愈（curing）。游离在中的λ可以进行，产生多个拷贝，并合成头部和尾部蛋白，包装成完整的λ噬菌体，使细胞裂解，释放出λ噬菌体再感染新的细胞。（图8-19）。因为λ噬菌体的DNA也有整合在染色体上和游离于中两种状态，所以也称做。但和F因子不同，λ噬菌体有细胞外形式，而F因子无细胞外形式。
新手上路我有疑问投诉建议参考资料 查看Qβ噬菌体_百度百科
关闭特色百科用户权威合作手机百科 收藏 查看&Qβ噬菌体本词条缺少概述、信息栏，补充相关内容使词条更完整，还能快速升级，赶紧来吧！ 侵染大肠杆菌（Ecoli）的一种噬菌体.通常侵M染其进行接合的供体菌株，并特异地吸附在此菌的性纟散毛上.其形态为无尾部的多面体，直径约25纳米（nm）。核酸为单链RNA，具有mRNA功能，即为“+”RNA.噬菌体基因组复制时，其负链是以亲本基因组（即正链RNA）为模板合成的，其新的基因组（即正链RNA）又进一步在负链上合成.成熟病毒粒子的形成，大部或全部通过自我装配完成.参 考 资 料1 噬菌体-概念
噬菌体是感染细菌、真菌、放线菌或螺旋体等微生物的细菌病毒的总称，本世纪初由D.Herelle和Twort各自独立于葡萄球菌和志贺菌中发现的。作为病毒的一种，噬菌体具有病毒特有的一些特性：个体微小；不具有完整细胞结构；只含有单一核酸。噬菌体基因组含有许多个基因，但所有已知的噬菌体都是在细菌细胞中利用细菌的核糖体、蛋白质合成时所需的各种因子、各种氨基酸和能量产生系统来实现其自身的生长和增殖。一旦离开了宿主细胞，噬菌体既不能生长，也不能复制。 噬菌体-种类
因为噬菌体主要由蛋白质外壳和核酸组成，所以，可以根据蛋白质外壳或核酸的结构特点对噬菌体进行分类。 根据蛋白质结构分类：无尾部结构的二十面体：这种噬菌体为一个二十面体，外表由规律排列的蛋白亚单位——衣壳组成，核酸则被包裹在内部。有尾部结构的二十面体：这种噬菌体除了一个二十面体的头部外，还有由一个中空的针状结构及外鞘组成的尾部，以及尾丝和尾针组成的基部。线状体：这种噬菌体呈线状，没有明显的头部结构，而是由壳粒组成的盘旋状结构。 迄今已知的噬菌体大多数是有尾部结构的二十面体，这是因为正多面体是多面体里最简单的结构，搭建起来最容易，所以病毒喜欢采用正多面体的结构。而正多面体一共又只有五种，分别是正4, 6, 8, 12, 20面体，其中正20面体是最接近球形的，也就是在体积相同的情况下，需要更少的材料，更为节省。 根据核酸特点分类： ssRNA：噬菌体中所含的核酸是单链RNA。 ds RNA：噬菌体中所含的核酸是双链RNA。 ssDNA：噬菌体中所含的核酸是单链DNA。 ds DNA：噬菌体中所含的核酸是双链DNA。
噬菌体-噬菌机理
噬菌体颗粒感染一个细菌细胞后可迅速生成几百个子代噬菌体颗粒，每个子代颗粒又可感染细菌细胞，再生成几百个子代噬菌体颗粒。如此重复只需4次，一个噬菌体颗粒便可使几十亿个细菌感染而死亡。当把细菌涂布在培养基上，长成一层菌苔时，一个噬菌体感染其中一个细菌时，便会同上面所说的那样，把该细菌周围的成千上万个细菌感染致死，在培养基的菌苔上出现一个由于细菌被噬菌体裂解后造成的空斑，这便称为噬菌斑(plaque)。每一噬菌体除了能使宿主细菌裂解死亡外，还有一些噬菌体感染细菌后，并不使细胞死亡，称为温和噬菌体，这些噬菌体感染细菌后，将其自身的基因组整合进宿主细胞的基因组，此时，这种宿主细菌称为溶原性细菌。溶原性细菌内存在的整套噬菌体DNA基因组称为原噬菌体(prophage)，溶原性细菌不会产生许多子噬菌体颗粒，也不会裂解；但当条件改变使溶原周期终止时，宿主细胞就会因原噬菌体的增殖而裂解死亡，释放出许多子代噬菌体颗粒。溶原性细菌有两个特点。第一，溶原性细菌在被噬菌体感染并溶原化后，不会被同种噬菌体再次感染，这是超感染免疫性。第二，经过若干世代后，溶原性细菌会开始进入溶菌周期，即溶原性细菌的诱发。此时，原噬菌体从宿主基因组上切离下来进行增殖。 侵染过程 一个典型的噬菌体的侵染细菌的过程，可以分为三个阶段：感染阶段、增殖阶段和成熟阶段。 感染阶段：噬菌体侵染寄主细胞的第一步是“吸附”，即噬菌体的尾部附着在细菌的细胞壁上，然后进行“侵入”。噬菌体先通过溶菌酶的作用在细菌的细胞壁上打开一个缺口，尾鞘像肌动球蛋白的作用一样收缩，露出尾轴，伸入细胞壁内，如同注射器的注射动作，噬菌体只把头部的DNA注入细菌的细胞内，其蛋白质外壳留在壁外，不参与增殖过程。增殖阶段：噬菌体DNA进入细菌细胞后，会引起一系列的变化：细菌的DNA合成停止，酶的合成也受到阻抑，噬菌体逐渐控制了细胞的代谢。噬菌体巧妙地利用寄主(细菌)细胞的“机器”，大量地复制子代噬菌体的DNA和蛋白质，并形成完整的噬菌体颗粒。噬菌体的形成是借助于细菌细胞的代谢机构，由本身的核酸物质操纵的。据观察，当噬菌体侵入细菌细胞后，细菌的细胞质里很快便充满了DNA细丝，十分左右开始出现完整的多角形头部结构。噬菌体成熟时，这些DNA高分子聚缩成多角体，头部蛋白质通过排列和结晶过程，把多角形DNA聚缩体包围，然后头部和尾部相互吻合，组装成一个完整的子代噬菌体。成熟阶段：噬菌体成熟后，在潜伏后期，溶解寄主细胞壁的溶菌酶逐渐增加，促使细胞裂解，从而释放出子代噬菌体。在光学显微镜下观察培养的感染细胞，可以直接看到细胞的裂解现象。T2噬菌体在37 ℃下大约只需四十分就可以产生100～300个子代噬菌体。子代噬菌体释放出来后，又去侵染邻近的细菌细胞，产生子二代噬菌体。 噬菌体-应用
由于噬菌体可以将基因插入宿主DNA内的特性，使得它成为了重要的分子和遗传学研究工具。利用噬菌体，可以设计很多精巧的实验。下面，举出一项噬菌体应用的最具代表性的例子。 证明DNA是遗传物质：历史上，生物学家在细胞中总是没有办法找到承担遗传功能的物质，曾经一度认为蛋白质是遗传物质，因为它承担了生命活动的绝大部分功能。但是，1952年赫尔希(Hershey)和沙斯(Chase)两人利用噬菌体证明了DNA的遗传功能，为最终确立DNA是主要的遗传物质奠定了基础。他们把宿主细菌分别培养在含有35S和32P的培养基中,宿主细菌在生长过程中，就分别被35S和32P所标记。然后，赫尔希等人用T2噬菌体分别去侵染被35S和32P标记的细菌。噬菌体在细菌细胞内增殖，裂解后释放出很多子代噬菌体，在这些子代噬菌体中，前者被35S所标记，后者被32P所标记。接着，他们用被35S和32P标记的噬菌体分别去侵染未标记的细菌，然后测定宿主细胞的同位素标记。当用35S标记的噬菌体侵染细菌时，测定结果显示，宿主细胞内很少有同位素标记，而大多数35S标记的噬菌体蛋白质附着在宿主细胞的外面；当用32P标记的噬菌体感染细菌时，测定结果显示宿主细胞的外面的噬菌体外壳中很少有放射性同位素32P，而大多数放射性同位素32P在宿主细胞内。以上实验表明，噬菌体在侵染细菌时，进入细菌内的主要是DNA，而大多数蛋白质在细菌的外面。可见，在噬菌体的生活史中，只有DNA是在亲代和子代之间具有连续性的物质。因此，DNA是遗传物质。 噬菌体-参考资料 《Brock Biology of Microorganisms》，11 edition。 噬菌体λ噬菌体β系数β-胡萝卜素β测试相 关 词 条:噬菌体 |QQ三国 |QQ幻想 |β测试 |QQ对战平台 |相 关 词 条:噬菌体 |什么是噬菌体 |相 关 词 条:噬菌体展示技术 |噬菌体展示 |噬菌体载体 |m13噬菌体|噬菌体抗体库 |温和噬菌体 |噬菌体感染实验|噬菌体肽库 |噬菌体密码防盗专家 |噬菌体污染 |Infection of Escherichia coli (Ecoli) as a bacteriophage.Usuallyin carrying out their invasion of M dye bonding donor strain, and specific to the nature of the bacteria adsorbed on the loose hair on the Si. The shape of thepolyhedronwithout a tail, a diameter of about 25 nm (nm). Single-stranded nucleic acid RNA, with mRNA function, namely, & & RNA. Phage genome replication, its negative strand is parental genome (ie, positive-strand RNA) as template synthesis, and its new genome (ie, positive-strand RNA) further synthesis of the negative chain. the formation of mature virusparticles, most or all of the completed through self-assembly. Reference 1 phage - the concept of phage infection of bacteria, fungi, actinomycetes, or spirochete microorganisms such as bacteria and viruses in general, this beginning of the century by D. Herelle and Twort separate from Staphylococcus aureus and Shigella were found. As a kind of virus, bacteriophage with a virus, a number of unique features: do not have the integri contains only a single nucleic acid. Phage genome contains many genes, but all known phages are bacterial cells, the use of bacterial ribosomes, protein synthesis required for a variety of factors, various amino acids and energy generation systems to achieve their own growth and proliferation . Once left the host cell, phage can not grow, it can not copy. Phage - mainly by species because the phage protein and nucleic acid composition of shell, so the protein shell, or nucleic acids based on the structural characteristics of the phage classification. According to Structural Classification of Proteins: no tail structure of the icosahedron: a bacteriophage as an icosahedron, appearance by the regular arrangement of protein sub-units - the capsid composition, nucleic acid was wrapped in house. A tail structure of the icosahedron: This phage addition to the head of an icosahedron, there by a hollow needle-like structure and the composition of the tail sheath, and the tail end ofwireand formed the base of the needle. Linear body: This phage was linear, there is noobvioushead structures, but by thespiralshell-like structure composed of particles. To date the majority of the known phage tail structure is icosahedron, it is because regular polyhedron is a polyhedron the most simple structure, built up and most likely, so the virus prefer regular polyhedron structure. The polyhedron is also a total of only five, namely, being 4, 6, 8, 12, 20 icosahedron, which is the closest being 20-sided spherical, that is, the same volume of cases, require less material, more economical . According to nucleic acid characterized byCategory: ss RNA: DNA contained in bacteriophage is a single-stranded RNA. ds RNA: phage contained double-stranded nucleic acid is RNA. ss DNA: phage contained in the single-stranded nucleic acid is DNA. ds DNA: phage contained double-stranded nucleic acid is DNA. Phage - phagocytic mechanism of phage particles after infection of a bacterial cell can rapidly produce hundreds of offspring phage particles, each particle can also progeny of bacteria infected cells, which in turn produce hundreds of offspring phage particles. Repeat only four times, a phage particle would allow billions of bacterial infection and death. When the coating of bacteria in the culture medium, the bacteria grow into a layer ofmoss, a phage infection in one of the bacteria, they in conjunction with the above stated, to the bacteria surrounding the death of thousands of bacterial infection, in the medium The bacteria appeared on a moss was due to phage lysis of bacteria caused by plaque, which is referred to as plaque (plaque). In addition to enable the host for each phage lysis of bacteria killed, there are a number of bacteria after phage infection does not make cell death, known as the moderate phage, the phage infection of bacteria, will be its own genome integrated into the host cell genome, this , this is called the host bacterium lysogenic bacteria. Lysogenic bacteria exist in the set of phage genomic DNA is called prophage (prophage), lysogenic bacterium does not produce a number of sub-phage particle,
when conditions have changed so that Lysogenic cycle ends, the host cells a result of the proliferation and cracking of the original phage death, releasing a number of progeny phage particles. Lysogenic bacteria have two characteristics. First, the lysogenic bacteria by phage infection and lysogenic removed, will not be the same kinds of phage re-infection, which is super-infection immunity. Second, after several generations, the lysogenic bacteria will begin to enter the lytic cycle of pathogenic bacteria induce instant. At this point, the original phage from the host genome to carry out a cut from the proliferation. Infection process of a typical bacteriophage infecting bacteria in the process can be divided into three stages: the stage of infection, proliferation stage and mature stage. Infection stages: the first step in phage infection of host cells are &absorption&, that is attached to the tail of bacteriophage bacterial cell wall, and then to &invasion.& To pass the role of phage lysozyme in the bacterial cell wall to open a gap, tail sheath, like the role of actin-myosin contraction, like, exposing the tailshaft, stretching from within the cell wall, as the syringe injection action, only the head of bacteriophage DNA injection bacterial cells, the protein shell stay in the wall outside, not involved in the proliferation process. Proliferative stages: phage DNA into bacterial cells, will cause a series of changes: cessation of bacterial DNA synthesis, enzyme synthesis is also subject to inhibition, phage gradually controlling the cell metabolism. Clever use of phage-host (bacterial) cells, the &machine& to copy a large number of progeny phage DNA and proteins, andform acomplete phage particles. The formation of phage-bacterial cell metabolism by means of institutions, by their manipulation of nucleic acid material. It has been observed, when the phage invade bacterial cells, the bacteria inside the cytoplasm soon filled with DNA filaments, very full set of polygons around the head structure. Phage mature, these DNA polymer poly shrunk to polyhedrin, head through the arrangement of protein and crystallization process, the polygonal body surrounded by DNA condensation, and then the head and tail coincide with each other, assemble into a complete phage progeny. Mature stage: bacteriophage mature in the late incubation, dissolved lysozyme gradually increase the host cell wall to facilitate cell lysis, thereby releasing progeny phage. Observed under theopticalmicroscope, cultured infected cells can directly see the phenomenon of cell lysis. T2 phage at 37 ℃ for approximately can be produced only four great 100 ~ 300 sub-generation of phage. Progeny phage released after the infection went to the neighboring bacterial cells, resulting in sub-second generation phage. Phage - Applications can be due to phage DNA within the gene was inserted into the host properties, making it an important tool for molecular and genetic research. The use of phage can be designed a lot of clever experiments.Next, a phage applications cited the most representative example. Prove that DNA is the genetic material: Historically, biologists in the cell always assume there is no way to find the genetic function of the material, once that the protein is the genetic material, because it assumed thevastmajority of functional life activities. However, in 1952, Hershey (Hershey), and Chase (Chase) both proved that the use of phage DNA, the genetic features, for the eventual establishment of the genetic material DNA is the main foundation. They host bacteria were cultured in medium containing 35S and 32P, the host bacteria in the growth process, they were marked by 35S and 32P. Then, Hershey and others were to go with the T2 phage infection by 35S and 32P labeled bacteria. Phage in the bacterial cell proliferation, lysis and release many phage progeny, in which progeny phage, the former was marked by 35S, which was marked by 32P. Then, they used were 35S and 32P, respectively labeled phage to infect unlabeled bacteria, and then measured the isotope-labeled host cells. When using 35S labeled phage infection of bacteria, the measured results show that very few host cells isotope-labeled, while the majority of 35S labeled phage proteins in host cells att When using 32P labeled phage infection of bacteria, the measured The results showed that the phage host cell on the outside shell few radioisotopes 32P, while the majority of the radioisotope 32P in host cells. The aboveexperimentalresults show that phage in the infection when bacteria enter the bacteria are mainly DNA, while most proteins in bacteria outside. Can be seen in the phage&s life cycle, only the DNA in the parental generation andthe offspringof continuity between the substances. Thus, DNA is the genetic material. Phage - Reference &Brock Biology of Microorganisms&, 11 edition. Bacteriophage λ phage β-carotene, β β coefficient test-related term: bacteriophage | QQ Three Kingdoms | QQ Fantasy | β test | QQBattlePlatform | Related entries: bacteriophage | What is a bacteriophage | Related entries: phage display technology | phage display | phagevector|m13phage | phage antibody library | moderate phage | bacteriophage infection experiment | phage peptide library | password security experts phage | bacteriophage contamination |
新手上路我有疑问投诉建议参考资料 查看辅助噬菌体_百度百科
关闭特色百科用户权威合作手机百科
收藏 查看&辅助噬菌体本词条缺少概述、名片图，补充相关内容使词条更完整，还能快速升级，赶紧来吧！能产生重要蛋白质追&&&&查
这种噬菌体编码产生另一些噬菌体所不能产生的重要蛋白质，使另一些噬菌体得以生长和繁殖。这种噬菌体编码产生另一些噬菌体所不能产生的重要蛋白质，使另一些噬菌体得以生长和繁殖。
噬菌体是由D.Herelle和Twort各自独立发现的。噬菌体(bacteriophage, phage)是感染细菌、真菌、放线菌或螺旋体等微生物的的总称，因部分能引起宿主菌的裂解，故称为噬菌体。本世纪初在葡萄球菌和志贺菌中首先发现。噬菌体具有病毒的一些特性：个体微小。噬菌体含有许多个，但所有已知的噬菌体都是细菌细胞中利用细菌的、蛋白质合成时所需的各种因子、各种氨基酸和能量产生系统来实现其自身的生长和增殖。一旦离开了细胞，噬菌体既不能生长，也不能复制。
噬菌体分布极广，凡是有细菌的场所，就可能有相应噬菌体的存在。在人和动物的排泄物或污染的井水、河水中，常含有肠道菌的噬菌体。在土壤中，可找到土壤细菌的噬菌体。噬菌体有严格的宿主特异性，只寄居在易感宿主菌体内，故可利用噬菌体进行细菌的流行病学鉴定与分型，以追查。由于噬菌体结构简单、基因数少，是分子生物学与基因工程的良好实验系统。噬菌体颗粒在结构上有很大差别，一般可分成三种类型，即无尾部结构的二十面体，有尾部结构的二十面体和线状体，迄今已知的噬菌体大多数是有尾部结构的二十面体。
噬菌体有毒（烈）性噬菌体和温和噬菌体两种类型。侵入宿主细胞后，随即引起宿主细胞裂解的噬菌体称作毒性噬菌体。毒性噬菌体被看作正常表现的噬菌体。温和噬菌体则是：当它侵入宿主细胞后，其核酸附着并整合在宿主染色体上，和宿主核酸同步复制，宿主细胞不裂解而继续生长。这种不引起宿主细胞裂解的噬菌体称作温和噬菌体。
噬菌体颗粒感染一个细菌后可迅速生成几百个子代噬菌体颗粒，每个子代颗粒又可感染细菌细胞，再生成几百个子代噬菌体颗粒。如此重复只需4次，一个噬菌体颗粒便可使几十亿个细菌感染而死亡。当把细菌涂布在培养基上，长成一层菌苔时，一个噬菌体感染其中一个细菌时，便会同上面所说的那样，把该细菌周围的成千上万个细菌感染致死，在培养基的菌苔上出现一个由于细菌被噬菌体裂解后造成的空斑，这便称为噬菌斑(plaque)。每一噬菌体除了能使宿主细菌裂解死亡外，还有一些噬菌体感染细菌后，并不使细胞死亡，称为温和噬菌体，这些噬菌体感染细菌后，将其自身的基因组整合进宿主细胞的基因组，此时，这种宿主细菌称为溶原性细菌。溶原性细菌内存在的整套噬菌体DNA基因组称为原噬菌体(prophage)，溶原性细菌不会产生许多子噬菌体颗粒，也不会裂解；但当条件改变使溶原周期终止时，宿主细胞就会因原噬菌体的增殖而裂解死亡，释放出许多子代噬菌体颗粒。
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收藏 查看&粘粒载体本词条缺少名片图，补充相关内容使词条更完整，还能快速升级，赶紧来吧！
粘粒载体（cosmid vector），又称科斯质粒载体。是指一类含有λ噬菌体的cos序列的质粒载体。外文名cosmid vector领&&&&域生物学
粘粒（cosmid）实际是质粒的衍生物，是带有cos 序列的质粒。 cos序列是λ噬菌体 DNA 中将 DNA 包装到噬菌体颗粒中所需的 DNA 序列。粘粒的组成包括质粒复制起点（colE1），抗性标记（ampr）， cos 位点，因而能象质粒一样转化和增殖。它的大小一般 5-7kb 左右，用来克隆大片段 DNA ，克隆的最大 DNA 片段可达 45kb 。有的粘粒载体含有两个 cos 位点，在某种程度上可提高使用效率。[1]粘粒克隆的主要原理类似λ噬菌体载体。在外源片段与载体连接时，粘粒载体相当于λ噬菌体载体的左右臂，cos 位点通过粘端退火后，再与外源片段相间连接成多联体。当多联体与λ噬菌体包装蛋白混合时，λ噬菌体 A 基因蛋白的末端酶功能将切割两个 cos 位点，并将两个同方向 cos 位点之间的片段包装到λ噬菌体颗粒中去。这些噬菌体颗粒感染大肠杆菌时，线状的重组 DNA 就象 λ噬菌体 DNA 一样被注入细胞并通过 cos 位点环化，这样形成的环化分子含有完整的粘粒载体，可象质粒一样复制并使其宿主获得抗药性。因而，带有重组粘粒的细菌可用含适当抗生素的培养基挑选。通过这种方式，就将外源 DNA 片段通过粘粒载体克隆到大肠杆菌中了。
与λ噬菌体载体不同的是，外源片段克隆在粘粒载体中是以大肠杆菌菌落的形式表现出来的，而不是噬菌斑。这样所得到的菌落的总和就构成了基因文库。
上述带有外源片段的重组粘粒，可再次包装到噬菌体颗粒中去。通过辅助λ噬菌体的感染或诱导潜伏原噬菌体的生长，重组粘粒的 cos位点可作为包装的底物，导致重组粘粒 DNA 被包装到噬菌体颗粒中去。这些转导性颗粒从细胞中释放出来，既可无限期贮存，也可直接感染其他菌株。
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