Components of Experiment

Enterococcus faecalis is a gram positive bacterium normally residing in human intestine as a component of natural flora. It may act as a pathogen, however, for people with impaired immune system. Enterococcus faecalis is very efficient in acquiring resistance to antibiotics. One of its strains has been identified to be resistant to vancomycin—a drug that is traditionally used as the last resort. Enterococcus faecalis transfers resistance to antibiotics within and across species. The transfer process of antibiotic resistance takes place through the transfer of plasmids— small circular DNA with genes encoded for antibiotic resistance. The most common and powerful way to transfer plasmids is conjugation. In our experiment, during the process of conjugation, cells without the desired plasmid (recipient cells) release signaling molecules (cCF10) into the environment, and induce the host cells (donor cells) with the desired plasmid. Once the donor cells are induced, they will conjugate with recipient cells and transfer the plasmid of interest—pCF10 which contains genes for antibiotic resistance, to the recipient cells. The initial recipient cells are thus converted to transconjugant cells, capable of acting as donor cells eventually. In order to prevent self-induction by the cCF10 generated by donor cells themselves, donor cells produce an inhibiting signaling pheromone, iCF10. cCF10 and iCF10 competeswith each other, and only when cCF10 exists in a high enough concentration would the donor cells be induced