PHOTODYNAMIC INACTIVATION OF BACTERIOPHAGE

Abstract

The extensive literature on the photosensitizing action of dyes on biological systems has been summarized by Blum (1941). Reference should be made to this book for the general principles of photodynamic action. Previous studies on photo-dynamic inactivation of phages have been made by Clifton (1931) and by Perdrau and Todd (1933). Burnet (1933) found that the relative sensitivity of phage strains to photodynamic inactivation was correlated with serological grouping and hence was of taxonomic signifi-cance. The present paper is a kinetic study of the variables affecting photodynamic ssitivity. MTEIALS AND METHODS The phage strains and bacterial hosts used are listed in table 1 with references to the ultimate source. Routine methods of phage technology have been described by Adams (1950). The saline buffer diluent contained 0.85 per cent NaCl, 100 pg of gelatin per ml, 0.001 M MgSO4; and it was buffered at pH 7.0 with the appropri-ate mixture of m/15 Na2HPO04 and m/15 KH2PO4. The methylene blue dye was National Aniline Certified, 84 per cent dye content, and was dis-solved in the saline diluent at a concentration of one g of dye per 10 liters of solution (K0,OOO). A %, dilution of this stock solution had an optical density of 0.650 in the Beckman spectro-photometer at the absorption peak of 665 mu. The light source was a 15 watt GE fluorescent light in a Fisher illuminator with reflector. For most experiments the distance from lamp to irradiated mixture was 25 cm. All experiments were performed in a dark room illuminated only by a dim green bulb which caused no detectable inactivation of photosensitized phage. The phage was diluted to about 108 particles