phthalocyanines on Escherichia coli

Escherichia colt, as most Gram-negative bacteria, is insensitive to the photosensitizing ac-tion of both fipid-sohible Zinc-phihalocyanine (Zn-Pc) and water-soluble Zinc-mono/disulfo-nated phthalocyanine (Zn-PcS). Photosensitivity can be induced by alteration of the outer mem-brane, as obtained by either induction of com-petence or treatment with Tris-EDTA. Both phthalocyanines largely bind at the level of the cytoplasmic membrane; however, Zn-PcS shows a superior photosensitizing activity as compared with Zn-Pc. Biochemical analyses performed on irradiated ceils suggest that the cytoplasmic mem-brane is an important arget of the photoprocess, while DNA is not involved. 2