Exogenous 4-hydroxybenzoate can restore the quinone pool for cells bearing a <i>ubiA</i>(<i>Q253P</i>) mutation.

a<p>Both strains bore Δ<i>flhB</i> mutations.</p>b<p>For exponential phase, cells were harvested at OD₆₀₀ 0.6.</p>c<p>For cells in stationary phase, ubiquinone-8 (UQ-8) and menaquinone-8 (MK-8) were detected.</p>d<p>Standard deviations are shown for measurements performed in triplicate.</p>