第三节各类病毒及其繁殖方式.ppt

第三节 各类病毒及其繁殖方式,一、原核生物的病毒噬菌体,噬菌体：是病毒中的一种，一般把侵染细菌、放线菌的病毒叫噬菌体。（把侵染真菌的病毒叫噬真菌体）噬菌体在自然界广泛存在，在1995年发表的ICTV的病毒分类与命名第六次报告中共报道了4000余种，分别划归为49个病毒科.据Bradley(1967)归纳，噬菌体共有六类形态。,1.形态与分类,噬菌体共有六类形态：,T-系噬菌体T-系噬菌体是研究的最广泛而又深入的细菌噬菌体，按发现的先后顺序进行从T1-T7编号，后来发现其中偶数者的形态都相同（蝌蚪形收缩性长尾），故统称T偶数噬菌体。,由于绝大多数噬菌体为蝌蚪形，现以E.coli T4为例，介绍蝌蚪形噬菌体的结构：,大肠杆菌T4噬菌体构造,偶数噬菌体的形态构造,2.BACTERIOPHAGE LIFE CYCLES,Two primary types of bacteriophages：,温和噬菌体（temperate phrage）噬菌体感染细胞后，将其核酸整合（插入）到宿主的核DNA上，并且可以随宿主DNA的复制而进行同步复制，在一般情况下，不引起寄主细胞裂解的噬菌体。,烈性噬菌体（virulent phage）感染细胞后,能在寄主细胞内增殖，产生大量子代噬菌体并引起细菌裂解的噬菌体。,The lytic life cycle consists of the following steps:AdsorptionPenetrationReplicationMaturation Release。,(1)The Lytic Life Cycle of Lytic Bacteriophages,The bacteriophage binds to receptors on the bacterial cell wall.,The bacteriophage injects its genome into the bacteriums cytoplasm,Fig.2:Penetration,Fig.1:Adsorption,The bacteriophage genome replicates and bacteriophage components begin to be produced by way of the host bacteriums metabolic machinery.,The production of bacteriophage components and enzymes progresses.,Fig.4:Late Replication,Fig.3:Early Replication,The bacteriophage components assemble.,A bacteriophage-coded enzyme breaks down the peptidoglycan in the bacterial cell wall causing osmotic lysis.,Fig.6:Release,Fig.5:Maturation,Phage T4 infecting its host E.coli cell,Electron Micrograph of a T-even Bacteriophage with a Contractile Sheath,A=normal bacteriophage;B=bacteriophage after contraction of sheath,A(+)RNA can be translated into viral protein.(+)and(-)strands are complementary.,Transcription of Viral Nucleic Acid into Viral mRNA,