Fifty microliters of the overnight culture
was added to 50mL of fresh 2 × LB medium in a 500mL Erlenmeyer
flask and allowed to grow in the same conditions until it reached mid-exponential phase (OD650 ≈ 0.5), whereupon 3 × 109 E. coli
cells (estimated by measuring the OD650 of the culture, where an
OD650 of 1 is equivalent to a concentration of 109 bacteria/mL) were
transferred to 50 mL plastic centrifuge tubes and centrifuged at 3256 g
for 10 min in a Jouan C4.22 centrifuge (Jouan, Saint-Mazaire, France).