FIG 9 .
Effect of novobiocin on E. coli O2 and its ETT2 deletion mutant. Overnight-grown cultures were diluted 1:25 into fresh growth medium, grown until they reached OD600 of 0.4. One hundred microliters of the cell culture was added into 3 ml of Davis soft agar (0.7%), stirred, and poured on top of Davis plates. Disks 6 mm in diameter (Schleicher & Schuell) were placed at the plate center, and 5 µl of novobiocin (Sigma-Aldrich) stock solution (100 mg/ml) was added to each disk. The plates were incubated overnight at 30°C, and the novobiocin inhibition area was measured. The area of inhibition is shown in the photos in panel A and quantified in panel B.