alpha-beta-gamma-delta-tetrakis(4-n-trimethylaminophenyl)porphine and tetraphenylphosphonium

We analysed the porphyrin-induced photodynamic inactivation of the membrane functions of bacteria through the in situ monitoring of changes in respiration rates, membrane permeability and membrane potential, using electrochemical sensors, such as oxygen, K(+) and tetraphenylphosphonium (TPP(+)) electrodes. We used two cationic porphyrins, tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TTMAPP) and tetrakis(4-N-methylpyridinium)porphyrin (TMPyP), along with an anionic porphyrin, tetrakis(4-sulfonatophenyl)porphyrin (TSPP), as a negative control. TTMAPP and TMPyP inhibited the respiration of bacteria within minutes of photo-irradiation at a concentration of 1 μM, where the survival of bacteria decreased, while TSPP did not affect the bacteria. The respiration of Staphylococcus aureus cells (Gram-positive bacterium) was more strongly inhibited than that of Escherichia coli cells (Gram-negative bacterium). Increasing the concentration of porphyrin strengthened the respiratory inhibition. Although TTMAPP increased the permeability to K(+) of the cytoplasmic membranes of bacteria, the change was relatively slow. Cationic porphyrins, showing the strong respiratory inhibition of S. aureus cells, induced the dissipation of membrane potential within minutes of photo-irradiation, in accord with the time traces of respiratory inhibition. Such a correlation strongly supported that porphyrin-induced photo-inactivation of bacteria involved rapid damage to the energy-producing system of bacteria induced by inhibition of the respiratory chain, leading to a dissipation of membrane potential. These results are discussed in connection with the ability of porphyrins to generate singlet oxygen and bind to the bacterial cell envelope.

Topics: Cations; Cell Membrane Permeability; Electrochemical Techniques; Electrodes; Escherichia coli; Light; Membrane Potentials; Onium Compounds; Organophosphorus Compounds; Oxygen; Porphyrins; Potassium; Singlet Oxygen; Staphylococcus aureus

The photodynamic inactivation of the membrane functions of bacteria was analyzed in situ, using K(+) and tetraphenylphosphonium (TPP(+)) electrodes, as well as an oxygen electrode. Tetrakis(4-N-trimethylaminophenyl)porphine (TTMAPP) and rose bengal were used, since both dyes act strongly on bacteria, such as Staphylococcus aureus. After a short time lag, they inhibited the respiration of bacteria and increased the permeability of the cytoplasmic membrane to K(+), while dissipating the membrane potential. This combination of sensors is quite useful for visualizing the actions of photosensitizers on the bacterial membrane. TTMAPP and rose bengal impaired the bacterial function by reducing the membrane potential within minutes of photo-irradiation.

Topics: Anti-Bacterial Agents; Cell Membrane; Cell Membrane Permeability; Electrochemical Techniques; Electrodes; Light; Membrane Potentials; Onium Compounds; Organophosphorus Compounds; Photochemotherapy; Photosensitizing Agents; Porphyrins; Potassium; Rose Bengal; Staphylococcus aureus