MODE OF ACTION OF a-TERTHIENYL ON ESCHERICHIA COLI: EVIDENCE FOR A PHOTODYNAMIC EFFECT ON MEMBRANES
نویسندگان
چکیده
The photodynamic effects of sc-terthienyl (scT) in near-UV light (UV-A) on Escherichiu coli showed close agreement with the light absorption of scT at different wavelengths suggesting that r 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 otT/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 . co[i and a more resistant bacterium, Pseudomonas aeruginosa, was absolutely dependent on the presence of oxygen. The rate of killing by otT/UV-A showed a rather small dependence on preincubation temperatures. with quite rapid killing at 5°C. suggesting that the movement of otT across the cytoplasmic membrane of E. c-oli is not the rate limiting step in killing and perhaps is not even necessary for killing. Sodium dodecyl sulphate-polyacrylamide gels of cell membrane proteins after 15 and 30 min of treatment with rT/UV-A showed substantial random crosslinking of these proteins. The results taken overall suggest that rT is a photodynamic photosensitizer which exerts its primary effect at the level of the cytoplasmic membrane.
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