Fig 3.

N-Phenyl-1-naphthylamine (NPN) uptake assay to measure outer membrane permeability. Cells from VMM with mannitol were resuspended in 5 mM HEPES buffer (pH 7.2) to an approximate OD₆₀₀ of 0.5. dH₂O (95 μl), 0.5 mM NPN (5 μl), and cells (100 μl) were combined, and the fluorescence was measured every 2 min for 20 min. Viable plate counts were used to standardize the fluorescence data.