Hausmann R, Messerschmid M
Institut für Biologie III der Universität Freiburg, Federal Republic of Germany.
Mol Gen Genet. 1988 Jun;212(3):543-7. doi: 10.1007/BF00330862.
The gene expression of nine phages of the T7 group was compared after infection of Escherichia coli B(P1). With the exception of phage 13a which grew normally, all of them infected E. coli B(P1) abortively. Differences were found in the efficiency of host killing which ranged from 100% for phage 13a to 37% for phage A1122. Infection by T7 prevented colony formation by about 70% of the cells but they showed filamentous growth until about 2 h after infection. It was shown by SDS-polyacrylamide gel electrophoresis and autoradiography of [35S]methionine-labelled phage-coded proteins that all phages except for 13a showed measurable expression only of the early genes. No correlation was observed between killing capacity and the pattern of gene expression, and the ability to hydrolyse S-adenosyl-methionine (SAM, a cofactor for the P1 restriction endonuclease) by means of a phage-coded SAMase. Mixed infection of E. coli B(P1) with 13a and T7 yielded mixed progeny indistinguishable from that observed after mixed infection of the normal host E. coli B. Genetic crosses with amber mutants of 13a and T7 showed that the 13a marker opo+ (overcomes P one), required for growth on B(P1), is located in the early region, to the left of gene 1 (RNA polymerase gene).
在感染大肠杆菌B(P1)后，比较了T7组九个噬菌体的基因表达情况。除了能正常生长的噬菌体13a外，其他所有噬菌体感染大肠杆菌B(P1)均为流产感染。发现宿主杀伤效率存在差异，范围从噬菌体13a的100%到噬菌体A1122的37%。T7感染可阻止约70%的细胞形成菌落，但它们在感染后约2小时内呈现丝状生长。通过SDS-聚丙烯酰胺凝胶电泳和[35S]甲硫氨酸标记的噬菌体编码蛋白的放射自显影表明，除13a外的所有噬菌体仅显示早期基因的可检测表达。未观察到杀伤能力与基因表达模式以及通过噬菌体编码的S-腺苷甲硫氨酸酶（SAM，P1限制性内切酶的一种辅助因子）水解S-腺苷甲硫氨酸的能力之间存在相关性。大肠杆菌B(P1)与13a和T7的混合感染产生的混合后代与正常宿主大肠杆菌B混合感染后观察到的后代无法区分。与13a和T7的琥珀突变体进行遗传杂交表明，在B(P1)上生长所需的13a标记opo+（克服P1）位于早期区域，在基因1（RNA聚合酶基因）的左侧。
