Scholl D, Rogers S, Adhya S, Merril C R
National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Virol. 2001 Mar;75(6):2509-15. doi: 10.1128/JVI.75.6.2509-2515.2001.
A virulent double-stranded DNA bacteriophage, Phi K1-5, has been isolated and found to be capable of infecting Escherichia coli strains that possess either the K1 or the K5 polysaccharide capsule. Electron micrographs show that the virion consists of a small icosohedral head with short tail spikes, similar to members of the Podoviridae family. DNA sequence analysis of the region encoding the tail fiber protein showed two open reading frames encoding previously characterized hydrolytic phage tail fiber proteins. The first is the K5 lyase protein gene of Phi K5, which allows this phage to specifically infect K5 E. coli strains. A second open reading frame encodes a protein almost identical in amino acid sequence to the N-acetylneuraminidase (endosialidase) protein of Phi K1E, which allows this phage to specifically infect K1 strains of E. coli. We provide experimental evidence that mature phage particles contain both tail fiber proteins, and mutational analysis indicates that each protein can be independently inactivated. A comparison of the tail gene regions of Phi K5, Phi K1E, and Phi K1-5 shows that the genes are arranged in a modular or cassette configuration and suggests that this family of phages can broaden host range by horizontal gene transfer.
一种烈性双链DNA噬菌体Phi K1-5已被分离出来，发现它能够感染具有K1或K5多糖荚膜的大肠杆菌菌株。电子显微镜照片显示，病毒粒子由一个带有短尾刺的小型二十面体头部组成，类似于短尾噬菌体科的成员。对编码尾丝蛋白区域的DNA序列分析显示有两个开放阅读框，编码先前已鉴定的水解性噬菌体尾丝蛋白。第一个是Phi K5的K5裂解酶蛋白基因，它使这种噬菌体能够特异性感染K5大肠杆菌菌株。第二个开放阅读框编码一种蛋白质，其氨基酸序列与Phi K1E的N-乙酰神经氨酸酶（内切唾液酸酶）蛋白几乎相同，它使这种噬菌体能够特异性感染大肠杆菌的K1菌株。我们提供了实验证据，证明成熟的噬菌体颗粒含有两种尾丝蛋白，突变分析表明每种蛋白都可以独立失活。对Phi K5、Phi K1E和Phi K1-5的尾基因区域进行比较，结果表明这些基因以模块化或盒式结构排列，这表明该噬菌体家族可以通过水平基因转移来扩大宿主范围。
