This is a really interesting and thought-provoking article in mBio. The authors found that if they injected a high concentration of plasmid containing the gene encoding Shiga toxin (with native bacterial promoter), they saw that Shiga toxin was expressed and caused damage to mice, and toxin was detected in several different tissues & organs. If this is really true, then WOW!
The results of this study raise some interesting questions about the danger of eukaryote hosts potentially being able to express bacterial virulence factors encoded on plasmids. A commentary on this article discusses the transfer of virulence plasmids via bacteriophage and how, in light of the new findings, we now need to think about preventing phage spread of virulence factors and begin targeting phages.
Link to the article: http://mbio.asm.org/content/4/5/e00501-13.full
Link to commentary: http://mbio.asm.org/content/4/6/e00868-13.full