Conjugative DNA Transfer Is Enhanced by Plasmid R1 Partitioning Proteins.

Bacterial conjugation is a form of type IV secretion used to transport protein and DNA directly to recipient bacteria. The process is cell contact-dependent, yet the mechanisms enabling extracellular events to trigger plasmid transfer to begin inside the cell remain obscure. In this study of plasmid R1 we investigated the role of plasmid proteins in the initiation of gene transfer.

The transfer operon of plasmid R1 extends beyond finO into the downstream replication genes.

finO is the final gene in the 35.4 kb transfer operon of IncFI plasmid F that is known to be involved in self-conjugative transfer. The genetic region distal to finO separates the conjugation and replication control modules of IncFII plasmid R100 and carries uncharacterized genes not found in plasmid F.

Functional analysis of the finO distal region of plasmid R1.

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.