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Mode of action of alpha terthienyl on escherichia coli evidence for a photodynamic effect on membranes

Mode of action of alpha terthienyl on escherichia coli evidence for a photodynamic effect on membranes

Photochemistry & Photobiology 36(5): 517-524

The photodynamic effect of .alpha.-terthienyl (.alpha.T) in near-UV light (UV-A) on E. coli showed close agreement with the light absorption of .alpha.T at different wavelengths suggesting that .alpha.T is the primary absorbing molecule responsible for the photosensitized reaction. Studies with DNA repair deficient mutants of E. coli indicated that the bactericidal action of .alpha.T/UV-A was not mediated by DNA damage, in direct contrast to the well-known photosensitizer, 8-methoxypsoralen. By using a closed borosilicate glass reaction vessel and various gas mixtures, it was demonstrated that photosensitization of both E. coli and a more resistant bacterium, Pseudomonas aeruginosa, was absolutely dependent on the presence of O2. The rate of killing by .alpha.T/UV-A showed a rather small dependence on preincubation temperatures, with quite rapid killing at 5.degree. c, suggesting that the movement of .alpha.T across the cytoplasmic membrane of E. coli is not the rate limiting step in killing and perhaps is not even necessary for killing. Sodium dodecyl sulfate-polyacrylamide gels of cell membrane proteins after 15 and 30 min of treatment with .alpha.T/UV-A showed substantial random crosslinking of these proteins. .alpha.T is evidently a photodynamic photosensitizer which exerts its primary effect at the level of the cytoplasmic membrane.

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Accession: 005908095

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