School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia.
Plasmid. 2023 Jul;127:102698. doi: 10.1016/j.plasmid.2023.102698. Epub 2023 Jul 28.
An IncC or IncA plasmid is needed to enable transfer of SGI1 type integrative mobilisable elements but an IncC plasmid does not stably co-exist with SGI1. However, the plasmid is stably maintained with SGI1-K, a natural SGI1 deletion variant that lacks the sgaDC genes (S007 and S006) and the upstream open reading frame (S008) found in the SGI1 backbone. Here, the effect of the sgaDC genes and S008 on the stability of an IncC plasmid in an Escherichia coli strain with or without SGI1-K was examined. Co-transcription of the S008 open reading frame with the downstream sgaDC genes was established. When a strain containing SGI1-K complemented with a pK18 plasmid that included S008-sgaDC or sgaDC expressed from the constitutive pUC promoter was grown without antibiotic selection, the resident IncC plasmid was rapidly lost but loss was slower when S008 was present. In contrast, SGI1-K and the S008-sgaDC or sgaDC plasmid were quite stably maintained for >100 generations. However, the high copy number plasmids carrying the SGI1-derived S008-sgaDC or sgaDC genes constitutively expressed could not be introduced into an E. coli strain carrying the IncC plasmid but without SGI1-K. Using equivalent plasmids with S008-sgaDC or sgaDC genes controlled by an arabinose-inducible promoter, under inducing conditions the IncC plasmid was stable but the plasmid containing the SGI1-derived genes was rapidly lost. This unexpected observation indicates that there are multiple interactions between the IncC plasmid and SGI1 in which the transcriptional activator genes sgaDC play a role. These interactions will require further investigation.
需要 IncC 或 IncA 质粒才能实现 SGI1 型整合可移动元件的转移，但 IncC 质粒不能与 SGI1 稳定共存。然而，SGI1-K 可以稳定维持质粒，SGI1-K 是一种天然的 SGI1 缺失变体，缺少 SGI1 骨架中的 sgaDC 基因（S007 和 S006）和上游开放阅读框（S008）。在此，研究了 sgaDC 基因和 S008 对含有或不含有 SGI1-K 的大肠杆菌菌株中 IncC 质粒稳定性的影响。证实了 S008 开放阅读框与下游 sgaDC 基因的共转录。当含有 SGI1-K 并补充包含 S008-sgaDC 或由组成型 pUC 启动子表达的 sgaDC 的 pK18 质粒的菌株在没有抗生素选择的情况下生长时，常驻 IncC 质粒迅速丢失，但当存在 S008 时丢失速度较慢。相比之下，SGI1-K 和 S008-sgaDC 或 sgaDC 质粒在超过 100 代中得以相当稳定地维持。然而，带有 SGI1 衍生的 S008-sgaDC 或 sgaDC 基因的高拷贝数质粒不能被引入携带 IncC 质粒但没有 SGI1-K 的大肠杆菌菌株。使用具有 S008-sgaDC 或 sgaDC 基因的等效质粒，通过阿拉伯糖诱导型启动子控制，在诱导条件下，IncC 质粒稳定，但含有 SGI1 衍生基因的质粒迅速丢失。这一意外观察表明，IncC 质粒和 SGI1 之间存在多种相互作用，其中转录激活基因 sgaDC 发挥作用。这些相互作用需要进一步研究。
