A composition comprising recombinant, intact minicells that contain atherapeutic nucleic acid molecule is disclosed. Methods for purifying apreparation of such minicells also are disclosed. Additionally, a genetictransformation method is disclosed, which comprises (i) making recombinant,intact minicells available that contain a plasmid comprised of a first nucleicacid segment, and (ii) bringing the minicells into contact with mammaliancells that are engulfing-competent, such that the minicells are engulfed bythe mammalian cells, which thereafter produce an expression product of thefirst nucleic acid segment.
