Table 2

Bacteriostatic activity of antimicrobialsa

StrainMIC (μg/ml) of PL, PQ, or antimicrobial with or without PL or PQb
PLPQOxoOxo + 1/4 PLOxo + 1/4 PQAmpAmp + 1/4 PLAmp + 1/4 PQKanKan + 1/4 PLKan + 1/4 PQ
3568 (wild type)251030.83.23.2244848243
3574 (ΔsoxS ΔmarA)1551.50.60.60.61616161.51.51.5
3706 (ΔacrB)91030.10.10.1888111
  • a Cells were grown to mid-log phase in the absence or presence of 1/4 MIC of plumbagin or paraquat, diluted 5,000-fold in LB liquid medium or medium containing plumbagin or paraquat, mixed with various antimicrobials at 2-fold increments with concentrations in two staggered dilution series, and incubated overnight at 37°C with shaking.

  • b Abbreviations: PL, plumbagin (1/4 PL = PL at 1/4 MIC); PQ, paraquat (1/4 PQ = PQ at 1/4 MIC); Oxo, oxolinic acid; Kan, kanamycin; Amp, ampicillin.