Preparation of -SOC -TFB1 -TFB2 (pH was set to 5.6 instead of 5.8) -Agar plates (containing ampicillin (200 mg/L) or chloramphenicol (34 mg/L)) According to qiagen DNA protocols & application Modifications: -150 ml Glycerol per 1 L (15%) are added to TFB1 and TFB2 (instead of 15 mL) -1.4 g/l CaCl2 dihydrate are used in TFB1 -11.0 g/l CaCl2 dihydrate are used in TFB2 -SOC is sterilized by filtration (not autoclaved)