[名校联盟]江西省德兴一中-学生物+病毒(课件)资料讲解.ppt

* Adsorption: phage adsorbs to receptors on the bacterial cell wall. Penetration: phage injects its genome into the bacteriums cytoplasm. Early replication: phage genome replicates and phage components begin to be produced. Late replication: production of phage components progresses. Maturation: phage components assemble. Release: phage-coded lysozyme breaks down peptidoglycan causing lysis of the host bacterium. OR Phage inserts its genome into the bacterial nucleoid to become a prophage. As the bacterium replicates, the prophage replicates as a part of the nucleoid. 9.Rare spontaneous induction: phage replicates via the lytic life cycle. * 温和噬菌体：噬菌体感染细胞后，将其核酸整合（附着）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。 原噬菌体（或前噬菌体）： 即整合在宿主核DNA上的噬菌体的核酸。 溶原性细菌：指在核染色体上整合有原噬菌体的细菌。可进行正常生长繁殖,而不被裂解。 溶原性细菌的特点： 可稳定遗传：子代细菌都含有原噬菌体，均具有溶原性。 可自发裂解：温和噬菌体的核酸也可从宿主DNA上脱落下来，恢复原来的状态，进行大量的复制，变成烈性噬菌体，自发裂解几率10-2～10-5 。 可诱导裂解：用化学、物理方法诱导 具有“免疫性”：溶原菌对其本身产生的噬菌体或外来的同源的噬菌体不敏感，对同源噬菌体具免疫性，对非同源噬菌体没有免疫性。 可复愈：自然遗失前噬菌体，但不发生自发裂解和诱导裂解 溶源转变：由于溶原菌整合了温和噬菌体的核酸而使自己产生一些新的生理特征。 . Temperate Bacteriophages and Lysogeny A. Temperate phages are capable of lysogeny, a nonlytic relationship with their hosts B. In lysogeny, the viral genome (called a prophage) is integrated into the host DNA and is replicated with it; it does not kill (lyse) the host cell; the cells are said to be lysogenic (or are called lysogens) C. In the lysogenic state, the host cell cannot be superinfected by a virus of the same type (i.e., it has immunity to superinfection) D. It may switch to the lytic cycle at some later time; this process is called induction E. Conditions at the time of infection may determine whether the virus will establish a lytic infection or lysogeny F. Establishment of lysogeny (bacteriophage lambda) 1. Two sets of promoters are available to host RNA polymerase 2. A repressor protein may be made from genes adjacent to one of these promoters 3. If this repressor binds to its target operator before the other promot