The invention relates in one aspect to a pharmaceutical composition comprising a nucleic acid delivery vehicle for delivering a deliverable nucleic acid into a bacterial cell, wherein the delivery vehicle comprises a deliverable nucleic acid packaged into one or more bacteriophage coat proteins, and wherein the delivery vehicle is capable of infecting the bacterial cell to introduce the deliverable nucleic acid into the cell, following which the deliverable nucleic acid is capable of forming a plasmid in the cell and being transmitted to one or more different bacterial cells by conjugation and not by infection. Compositions including a pharmaceutical composition comprising the delivery vehicle, and methods involving use or manufacture of the delivery vehicle, are also disclosed.