Figure 1.

2-Dimensional chloroquine gel analysis comparing DNA supercoiling in BW25113 (wild-type) and JW1106 (ΔcobB) mutant strains. Plasmids pBAD/Thio and pCobB were extracted from LB cultures at OD₆₀₀ = 0.8. The first dimension electrophoresis was carried out in 0.8% agarose gel with TAE buffer containing 3 μg/ml chloroquine at 3 V/cm for 16 h. The agarose gel was then rotated 90° for electrophoresis in the second dimension with 25 μg/ml chloroquine in the TAE buffer. The schematic diagram shows the expected distribution of positively and negatively supercoiled DNA topoisomers following electrophoresis.