University of Graz, Institute of Molecular Biosciences, Humboldtstrasse 50, A-8010 Graz, Austria.
Plasmid. 2011 Mar;65(2):159-68. doi: 10.1016/j.plasmid.2010.12.002. Epub 2010 Dec 8.
The intergenic region linking conjugative transfer and replication copy control modules of IncF plasmids shows conservation of gene homology and organization. Genes distal to finO are coordinately expressed with the upstream transfer operon encoding the majority of conjugation genes in related plasmids. Here we investigate potential functions for these genes in copy number control and in processes related to conjugation: gene transfer, pilus specific phage infection and plasmid-promoted biofilm formation by an Escherichia coli host. We find that insertional inactivation of genes in the finO distal region reduced transcriptional read through into the downstream copB gene of plasmid R1. The mutant plasmid derivatives exhibited a reduced copy number compared to the wild type. Moreover all insertion mutant derivatives of plasmid R1-16 with aberrantly low copy numbers conferred poor biofilm forming ability to their hosts. The general mutagenesis thus identified plasmid stability genes as the only plasmid functions besides conjugation genes linked to plasmid-promoted biofilm production under these laboratory conditions. Our findings imply that a novel component of cis- or trans-regulation on the transcriptional level is important to normal R1 plasmid copy number regulation.
IncF 质粒中连接接合转移和复制拷贝控制模块的基因间区域显示出基因同源性和组织的保守性。finO 下游的基因与上游转移操纵子协同表达，该操纵子编码相关质粒中大多数接合基因。在这里，我们研究了这些基因在拷贝数控制和与接合相关的过程中的潜在功能：基因转移、菌毛特异性噬菌体感染和质粒促进大肠杆菌宿主生物膜形成。我们发现，finO 远端区域基因的插入失活减少了质粒 R1 中下游 copB 基因的转录通读。与野生型相比，突变质粒衍生物的拷贝数减少。此外，所有具有异常低拷贝数的质粒 R1-16 的插入突变衍生物赋予其宿主较差的生物膜形成能力。因此，一般的诱变鉴定出质粒稳定性基因是除了接合基因之外的唯一与实验室条件下质粒促进生物膜形成相关的质粒功能。我们的发现表明，在转录水平上的顺式或反式调节的一个新组件对于正常 R1 质粒拷贝数调节很重要。
