Difference between revisions of "Team:UMaryland/Description"

Antibiotic resistence is a necessary selection factor for transgenic bacteria using plasmids as vectors. This staple of genetic engineering has been met with opposition with valid claims that the addition of antibiotics to the environment harms native species and poses a risk to unwanted antibiotic resistence through lateral gene transfer.

The Hok/Sok system has naturally evolved in bacteria as a means of plasmid retention, and is capable of addressing the issue by providing a selection factor for plasmid retention without the dangers of antibiotics and risk of lateral gene transfer. The Hok (host killing) gene codes for a mRNA which lies dormant in its initial secondary structure. As it is degraded by exonuclease, it assumes a translatable secondary structure which produces an apoptosis triggering protein. The Sok (suppression of killing) gene codes for a mRNA transcript that binds to the Hok mRNA, preventing it from being translated. The complex is eventually degraded by nuclease. Hok has a half life of 20 minutes, while Sok has a half life of 30 seconds. As long as both genes are present, the cell remains alive. After cell division, should the cell not retain the plasmid of interest which contains Hok/Sok, Hok mRNA remains the cytoplasm for 20 minutes, while remaining Sok is degraded. Since the cell does not contain a Sok gene, no Sok is being produced to save the cell from being killed by Hok. This system is very similar to current antibiotic resistence systems, only without the necessecity for antibiotics themselves, resolving the issue of encironmentally safe plasmid retention.