An Environment-Sensitive Synthetic Microbial Ecosystem
Figure 1
Genetic background of the synthetic microbial ecosystem in this study.
Two engineered E.coli populations are co-cultured to benefit from each other via two different QS signals. PtetR was used as constitutive promoter in our experiments. RFP and GFP under the regulation of PtetR were used to distinguish ER and EG by using fluorescence microscope. EG and ER show background resistance to ampicillin and kanamycin respectively by introduction of plasmids PSB1A2 and PSB2K3 where different genetic circuits were organized. RhlR signal receptor was synthesized within ER and could bind with C4HSL signal produced by rhll gene in EG cells to activate Prhl promoter if the concentration of C4HSL reaches to threshold, which enables ER resistant to kanamycin. Similarly, 3OC6HSL can be synthesized by luxI gene in ER cells (controlled by Plac promoter, IPTG can be added to increase 3OC6HSL concentration, but even leaky expression can produce enough 3OC6HSL signal), and bind to LuxR signal receptor in EG to initiate LuxPR promoter, which makes EG tolerate to ampicillin. Thus individual EG and ER show tolerance to ampicillin and kanamycin respectively due to background vector resistance, while both have double resistance if two cells are co-cultured. RFP and GFP under the regulation of PtetR were used to distinguish ER and EG by using fluorescence microscope.