Waters V L, Crosa J H
J Bacteriol. 1986 Aug;167(2):647-54. doi: 10.1128/jb.167.2.647-654.1986.
The aerobactin iron uptake system genes in the prototypic plasmid pColV-K30 are flanked by inverted copies of insertion sequence IS1 and by two distinct replication regions. To address the question of how these flanking regions may facilitate the maintenance and spread of the aerobactin system among the plasmids and chromosomes of enteric species, we investigated the DNA environment of 12 ColV plasmids. We found that the aerobactin system-specific genes are conserved in every plasmid phenotypically positive for the aerobactin system. The upstream IS1 and its overlapping replication region (REPI) are also conserved. This replication region was cloned from several ColV plasmids and found to be functional by transforming these cloned derivatives into a polA bacterial host. In contrast, the downstream flanking region is variable. This includes the downstream copy of IS1 and the downstream replication region (REPII). We infer from these results that sequences in addition to the two flanking copies of IS1, in particular the upstream region including REPI, have been instrumental in the preservation and possible spread of aerobactin genes among ColV plasmids and other members of the FI incompatibility group.
典型质粒pColV-K30中的气杆菌素铁摄取系统基因两侧是插入序列IS1的反向重复序列以及两个不同的复制区域。为了解这些侧翼区域如何促进气杆菌素系统在肠道菌属的质粒和染色体之间的维持和传播，我们研究了12种ColV质粒的DNA环境。我们发现，气杆菌素系统特异性基因在每个表型上对气杆菌素系统呈阳性的质粒中都是保守的。上游的IS1及其重叠的复制区域（REPI）也保守。从几种ColV质粒中克隆出该复制区域，并通过将这些克隆衍生物转化到polA细菌宿主中发现其具有功能。相比之下，下游侧翼区域是可变的。这包括IS1的下游拷贝和下游复制区域（REPII）。我们从这些结果推断，除了IS1的两个侧翼拷贝外，特别是包括REPI的上游区域，在气杆菌素基因在ColV质粒和FI不相容组的其他成员中的保存和可能传播中发挥了作用。
