Studies on T H E Mechanism of T H E Photosensitized in - Activation of E

Photosensitized inactivation of microorganisms has been the subject of numerous studies, and various hypothetical reaction mechanisms have been proposed for the interpretation of the phenomenon. In spite of such extensive experimentation and theorizing, there still exists uncertainty concerning the inactivation processes. No at tempt will be made to review the subject since it has been analyzed and treated by Blum (1) and Arnow (2). I t is evident that photosensitized inactivation is dependent on a variety of experimental factors. However, the literature reveals that the influence of such factors has been determined in many diverse and isolated experiments which makes the over-all evaluation of the data difficult, I t was thought that, by studying a single system under various experimental conditions, a more satisfactory interpretation could be found. A methylene blue and E. coli system was selected, since the methylene blue oxidation-reduction cycle represents a reversible process, and the associated structural changes in the molecule are known.