Nejman Bozena, Loś Joanna M, Łoś Marcin, Wegrzyn Grzegorz, Wegrzyn Alicja
Department of Molecular Biology, University of Gdańsk, Gdańsk, Poland.
J Mol Microbiol Biotechnol. 2009;17(4):211-20. doi: 10.1159/000242447. Epub 2009 Oct 1.
Genes encoding Shiga toxins in pathogenic Escherichia coli strains (Shiga toxin-producing E. coli, STEC) are located on lambdoid prophages. However, studies on the replication of these phages were not reported to date.
Plasmids derived from Shiga toxin-converting phages were constructed, introduced into wild-type E. coli strain and studied using methods of molecular genetics.
The studied replicons behaved similarly to plasmids derived from bacteriophage lambda, and DNA sequence analysis revealed their high level of homology to the lambda replication region. Nevertheless, contrary to lambda and two of six tested plasmids, four tested replicons were able to replicate in the E. colidnaA46 mutant. Specific nucleotide differences, causing amino acid substitutions relative to wild-type lambda O and P proteins, appeared to be responsible for this phenotype.
We conclude that replicons of phages bearing Shiga toxin genes are functionally similar to that of bacteriophage lambda, however, some of them have important differences which influence replication regulation. Furthermore, our results may suggest that there are newly discovered molecular interactions in the DNA replication regulation of lambda and lambdoid phages. Hence, plasmids derived from lambdoid phages appear to be convenient models to study the replication of Shiga toxin-converting bacteriophages.
致病性大肠杆菌菌株（产志贺毒素大肠杆菌，STEC）中编码志贺毒素的基因位于λ样原噬菌体上。然而，迄今为止尚未见有关这些噬菌体复制的研究报道。
构建来源于志贺毒素转化噬菌体的质粒，将其导入野生型大肠杆菌菌株，并采用分子遗传学方法进行研究。
所研究的复制子表现得与来源于噬菌体λ的质粒相似，DNA序列分析显示它们与λ复制区域具有高度同源性。然而，与λ及六个测试质粒中的两个不同，四个测试复制子能够在大肠杆菌dnaA46突变体中复制。相对于野生型λO和P蛋白导致氨基酸替换的特定核苷酸差异似乎是造成这种表型的原因。
我们得出结论，携带志贺毒素基因的噬菌体复制子在功能上与噬菌体λ的复制子相似，然而，其中一些存在影响复制调控的重要差异。此外，我们的结果可能表明在λ和λ样噬菌体的DNA复制调控中存在新发现的分子相互作用。因此，来源于λ样噬菌体的质粒似乎是研究志贺毒素转化噬菌体复制的便捷模型。
