各類病毒及其繁殖方式

1、一、原核生物的病毒—噬菌體,噬菌體：是病毒中的一種，一般把侵染細(xì)菌、放線菌的病毒叫噬菌體。（把侵染真菌的病毒叫噬真菌體）噬菌體在自然界廣泛存在，在1995年發(fā)表的ICTV的病毒分類與命名第六次報(bào)告中共報(bào)道了4000余種，分別劃歸為49個(gè)病毒科.據(jù)Bradley(1967)歸納，噬菌體共有六類形態(tài)。,1.形態(tài)與分類,噬菌體共有六類形態(tài)：,★T-系噬菌體——T-系噬菌體是研究的最廣泛而又深入的細(xì)菌噬菌體，按發(fā)現(xiàn)的先后順序進(jìn)行從T1---

2、T7編號(hào)，后來(lái)發(fā)現(xiàn)其中偶數(shù)者的形態(tài)都相同（蝌蚪形收縮性長(zhǎng)尾），故統(tǒng)稱T偶數(shù)噬菌體。,由于絕大多數(shù)噬菌體為蝌蚪形，現(xiàn)以E.coli T4為例，介紹蝌蚪形噬菌體的結(jié)構(gòu)：,大腸桿菌T4噬菌體構(gòu)造,偶數(shù)噬菌體的形態(tài)構(gòu)造,2.BACTERIOPHAGE LIFE CYCLES,★Two primary types of bacteriophages ：,,溫和噬菌體（temperate phrage）——噬菌體感染細(xì)胞后，將其核酸整合（插入）到宿

3、主的核DNA上，并且可以隨宿主DNA的復(fù)制而進(jìn)行同步復(fù)制，在一般情況下，不引起寄主細(xì)胞裂解的噬菌體。,烈性噬菌體（virulent phage）——感染細(xì)胞后,能在寄主細(xì)胞內(nèi)增殖，產(chǎn)生大量子代噬菌體并引起細(xì)菌裂解的噬菌體。,◆The lytic life cycle consists of the following steps: Adsorption→Penetration→Replication→Mat

4、uration →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 bacterium's cytoplasm,Fig. 2: Penetr

5、ation,Fig. 1: Adsorption,,The bacteriophage genome replicates and bacteriophage components begin to be produced by way of the host bacterium's metabolic machinery.,,The production of bacteriophage components and enzy

6、mes 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.,

7、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 shea