PHOTODYNAMIC INACTIVATION OF BACTERIOPHAGE AND ITS INHIBITION

Abstract

Inactivation of the T-series of Escherichia coli phages by photodynamic action was studied using 25 dyes. Phage particles suspended in buffered [image]/60,000 solution of dyes were irradiated by visible light. Inactivation of phage particles was essentially an exponenital function of the time of irradiation. The velocity constants for various active dyes and 7 phages comprising 4 serological groups were measured. The order of activity of the dyes by serological group was as follows: T1 -methylene blue > toluidine blue > acridine orange, acrif lavine, brilliant cresyl blue; T3 and T7 -acridine orange > methylene blue > toluidine blue > acriflavine > brilliant cresyl blue; T5 -methylene blue > toluidine blue > acridine orange > acriflavine > brilliant cresyl blue. All dyes were inactive on the T2, T4, and T6 group. Phages in the same serological group showed similar sensitivities, but in different groups showed remarkably different sensitivities, suggesting that some phage constituents have a specific affinity for the dyes. The mechanism of the photodynamic action was studied using T5 as a test material. The results were interpreted by the hypothesis that phage particles have some receptor substance (substance, X, perhaps deoxyribonucleic acid) which combined reversibly with the dye to produce a potentially photosensitive complex, which upon excitation by visible light lead to inactivation of phage particles. Kinetic data of the photodynamic action fitted well the Michaelis-Menthen equation of enzyme kinetics. Some dyes (crystal violet and methyl green) which are structually similar to active dyes (methylene blue, and toluidine blue) inhibited the photodynamic action of the active dyes. Kinetic analysis showed that the dyes competed with each other for combination with the substance X.