The optimization system for preparation of TG1 competent cells and electrotransformation

An efficient electrotransformation system that includes electrocompetent cells is a critical component for the success of large-scale gene transduction and replication. The conditions of TG1 competent cell preparation and optimal electrotransformation were evaluated by investigating different parameters. Certain parameters for preparation of TG1 competent cells (≥8 × 10¹⁰ colony forming units (cfu)/μg DNA) include optimum culture time of monoclonal bacteria (8-10 hr), amplification growth concentration (approximately OD₆₀₀  = 0.45), and culture volume (400 ml in 2 L conical flask). With increased storage of competent cells at -80°C, electrotransformation efficiency gradually decreased, but it remains greater than ≥ 10¹⁰  cfu/μg DNA 3 months later. Moreover, the recovery time of electrotransformation also influenced electrotransformation efficiency (1.5-2 hr for optimization). The optimized transformation efficiency of TG1 (≥8 × 10¹⁰  cfu/μg DNA) was observed under suitable electric voltage (2.5 kV), electric intensity (15 kV/cm), and electric time (3.5 ms) of electricity for plasmid transformation. Optimized DNA amount (0.01-100 ng) dissolved in water led to the high efficiency of plasmid transformation (≥8 × 10¹⁰  cfu/μg DNA), but had low efficiency when dissolved in T4 ligation buffer (≤3 × 10¹⁰  cfu/μg DNA). These results indicated that an optimized TG1 transformation system is useful for high electrotransformation efficiency under general laboratory conditions. The optimized TG1 transformation system might facilitate large-scale gene transduction for phage display library construction.