Synthetic Symbiosis Ecosystem Based On LuxI/R And RhlI/R QS Signals

Symbiosis as a ubiquitous phenomenan has been widely applied in the field of medicine, energy and environment. In order to explore cell responses and symbiosis stability under the intimidation of antibiotics, combining with the conception and methods of synthetic biology, this study constructed an in silico and in vivo E.coli DH5αdouble strains (ER and EG) symbiosis system which responses to the existence of ampicillin and kanamycin based on QS signal transduction pathway. The results are as follows:(1) An artificial symbiosis system based on RhlI and LuxI/R is firstly designed and simulated by mathematical model. The results show that low initial cell density would lead to the collapse of this ecosystem and the cooperative relationship has different contributions to the survival of ER and EG with various concentrations of ampicillin and kanamycin. The distinguished resistance of two cells to antibiotic pressure also results in the imbalance of population density.(2) The symbiosis related functional genes are constructed by molecular biological methoad. ER and EG cells are tested to produce 3OC₆HSL and C4HSL signal moleculars respectively by LC-MS-MS and GC-TOF-MS; further research indicates ER cell could respond to C4HSL signals to survive in the culture with high concentration of kanamycin (1mg/ml), EG cell could respond to 3OC₆HSL signal to survive in the culture with high concentration of ampicillin (5mg/ml)(3) Further study displays that the lag phase of ER and EG are extended under high concentration of ampicillin and kanamycin, but ER is more competitive than EG. With fixed initial cell density, the symbiosis stability decreased to extinct with the increase of ampicillin and kanamycin concentration. For the ampicillin concentration of 4mg/ml and kanamycin concentration of 0.4mg/ml, the minimum initial concentrations required to maintain this symbiosis system are approximately 2×10⁶cells/ml for both ER and EG cells.