Extended Data Fig. 10. S. aureus and B. subtilis cells lacking UndP transporters remain polarized.

(a) Representative fluorescence and phase-contrast images of S. aureus wild-type and the ΔpopT ΔuptA (Δ2) mutant. The two strains were stained with the potentiometric dye 3,3’-Dipropylthiadicarbocyanine Iodide (DiSC3(5)). Treatment with the ionophore Gramicidin that depolarizes membranes was used as a positive control. The same cultures were separately stained with propidium iodide (PI) to assess the percentage of cells with membrane permeability defects. (b) Representative images of wild-type and the ΔuptA ΔykoX (Δ2) B. subtilis mutant stained with DiSC3(5). Gramicidin was used as a positive control for loss of membrane potential. Scale bar, 1 μm.