The Radiosensitivity of Escherichia coli and Streptococcus faecalis as Influenced by Vitamin K 5 and Its Analogs

Abstract

Six compounds structurally related to and including vitamin K₅ were examined for their ability to increase the lethal effects of gamma - radiation on E. coli and S. faecalis. Two compounds, 4-amino-1-naphthol and 1- amino-2-naphthol, increased the lethal effects of ionizing energy to a greater extent than vitamin K₅ for both test organisms. All three compounds were most effective sgainst E. coli only in the absence of oxygen. In contrast to this, S. faecalis was influenced both in the presence and in the absence of oxygen, although, in general, to a greater extent in its absence. In addition, menadione sodium bisulfite and 5-amino-lnaphthol were active against S. faecalis irradiated in a nitrogen atmosphere. The presence of the methyl group in vitamin K₅ is apparently responsible for this compound's being less effective than 4-amino-1-naphthol, and shifting the amino group to the adjacent ring in amino naphthol decreased or eliminated synergism. The implications of whether or not these compounds are exerting true enhancing or sensitizing mechanisms or a combination of these effects are discussed. (auth)