什麼是噬菌體

一類傳染細菌的複合病毒。發現於20世紀初，發現後不久即開始用來治療人類的腺鼠疫、霍亂等細菌疾病，但並不成功。1940年代隨着抗生素的出現被放棄。1990年代隨着抗藥細菌的興起，噬菌體的治療潛力再度獲得重視。噬菌體有成千上萬種，每一種可能只能侵染一類或幾類細菌。噬菌體的核心基因物質可能是核糖核酸（RNA）或去氧核糖核酸（DNA）。在噬菌體侵染宿主細胞時，這種裂解型噬體或毒性噬體會藉由裂解（迸裂）宿主細胞而釋放出複製的濾過性病毒粒子。其他種類（稱潛溶性噬體或溫和性噬體）會將核酸植入宿主的染色體內，以在細胞分裂中複製。在此期間，噬菌體是無毒性的。這種濾過性染色體組以後會變得活躍，開始產生濾過性病毒粒子，破壞宿主細胞。赫爾希和蔡斯（M. Chase）在1952年把噬菌體用於一項着名的實驗中，這個實驗支持了DNA是基因物質的理論。由於噬菌體染色體組很小，而且很多都能在實驗室製備，因此它們是分子生物學家最喜歡用的研究工具。對噬體的研究可幫助闡明基因的重組、核酸複製以及蛋白質合成。

bacteriophage

Any of a group of usually complex viruses that infect bacteria. Discovered in the early 20th century, bacteriophages were used to treat human bacterial diseases such as bubonic plague and cholera, but were not successful; they were abandoned with the advent of antibiotics in the 1940s. The rise of drug-resistant bacteria in the 1990s focused renewed attention on the therapeutic potential of bacteriophages. Thousands of varieties exist, each of which may infect only one or a few types of bacteria. The core of a bacteriophage's genetic material may be either DNA or RNA. On infecting a host cell, bacteriophages known as lytic or virulent phages release replicated viral particles by lysing (bursting) the host cell. Other types, known as lysogenic or temperate, integrate their nucleic acid into the host's chromosome to be replicated during cell division. During this time they are not virulent. The viral genome may later become active, initiating production of viral particles and destruction of the host cell. A. D. Hershey and Martha Chase used a bacteriophage in a famous 1952 experiment that supported the theory that DNA is the genetic material. Because bacteriophage genomes are small and because large quantities can be prepared in the laboratory, they are a favorite research tool of molecular biologists. Studies of phages have helped illuminate genetic recombination, nucleic-acid replication, and protein synthesis.