0.1 cm cuvette

For circuit characterization, plasmids of interest were electro-transformed into competent cells of E. coli JM109SGL. For electroporation, cells were first made electrocompetent by concentrating 100-folds and washing twice with ice-cold 10% glycerol and stored in −80 °C freezer before uses. Then, 50 μL of competent cells were mixed with 30–50 ng of the PCR products, and then electroporated at 1.8 kV with around 50 mA in an ice-cold 0.1 cm cuvette (Bio-Rad, USA), followed by the addition of 1 mL LB medium. After incubation at 37 °C for 1 h, cells were spread on agar plates with relevant antibiotics and grown for 12 h for colony selection via PCR analysis and sequencing. The positive colonies were selected for further study. For plasmid constructions, chemical competent E. coli DH5α were used to screen positive constructs of PCR assembly products. Five microliters of PCR products were mixed with 50 μL of competent cells after 30 min on ice. Followed by 45 s heat shock, cells were placed on ice for 2 min, then mixed with 0.95 mL fresh LB medium for 1 h incubation at 37 °C. Finally, 50 μL of incubated cells were spread on LB agar plate with relevant antibiotics and grown for 12 h for colony selections. All of the competent cells were stored at −80 °C before uses.