Reconstitution and localisation studies of a type IV secretion system

Abstract

Bacterial conjugation is the transport of a DNA molecule from a donor cell to a recipient. Since bacteria do not reproduce sexually, conjugation is a major contributor to prokaryotic genome plasticity and the spread of antibiotic resistance genes. A Type IV Secretion System (T4SS) mediates the DNA transport during conjugation. T4SSs are large macromolecular assemblies embedded in the membrane of bacteria, and are associated with pathogenesis, bacterial conjugation and natural transformation. They are a versatile family of secretion systems, who transport a wide variety of substrates, such as virulence proteins, DNA––protein complexes as well as only DNA. Here, we investigate the minimal requirements for conjugation, and the T4SS’s localisation within the cell. We show that the conjugative T4SS of the plasmid pR388 requires a total of 14 genes to efficiently mobilise DNA from a donor cell to a recipient cell and is arranged around the cell circumfence in a helical array. Our study of two reconstituted and fully functional conjugative T4SSs opens doors for further structural and functional analysis