Postsegregational killer loci for plasmid stability, phage exclusion, and antimicrobial killing

Postsegregational killing is the term used to describe the killing of cells that have lost a plasmid by a latent toxin or toxin precursor. The properties of the postsegregational killer loci were exploited to improve plasmid stability, better model plasmid loss, exclude bacteriophage, and use as an antimicrobial agent. In particular the hok/sok, parDE and pnd systems were studied in E. coli. A system containing to postsegregational killer loci was created and the stability measured and compared under the same conditions to systems with a no stability loci and single stability loci. Plasmid stability model was proposed that takes into account postsegregational killing for various reactor conditions. The hok/sok killer locus was shown to be able to exclude E. coli phage T4. The Hok peptide was studied for its use as an antimicrobial agent and shown to be unable to kill cells from outside the cell but permeated able to kill E. coli and P. putida.