Photodynamic action of the cationic dye tetrakis(N-ethylpyridinium-4-yl)porphyrin tetratosylate on Escherichia coli cell envelope

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We have analysed the photodynamic action of the cationic photosensitiser tetrakis(N-ethylpyridinium-4-yl)porphyrin tetratosylate (TN-Et-PyP) on the integrity and functions of E. coli AN 180 cell membranes. Photosensitisation of bacterial cells with photobactericidal concentrations of TN-Et-PyP resulted in abolition of plasma membrane (PM) voltage (ΔΨ), dissipation of transmembrane K+ gradient and inhibition of the respiratory activity of bacteria contemporary with enhanced accumulation of the lipophilic anion phenyldicarbaundecaborane (PCB–). Substantial impairment of cell PM functions suggests that the E. coli cell envelope, mainly at the level of PM, is a critical target of phototoxic action of TN-Et-PyP. Keywords: photosensitiser tetrakis(N-ethylpyridinium-4-yl)porphyrin tetratosylate (TN‑Et‑PyP), Escherichia coli, photodamage of cell membrane