Toxicity of singlet oxygen generated thermolytically in Escherichia coli

Three water-soluble derivatives of naphthalene endoperoxide were prepared to examine the toxicity of singlet oxygen towards Escherichia coli. On incubation without irradiation, these endoperoxides produce singlet oxygen thermolytically in a dose-dependent manner. The amount of singlet oxygen produced per unit time can be controlled by varying both the incubation temperature and the number of methyl substituents of the naphthalene endoperoxide derivatives. 3-(1,4-Dihydro-1,4-epidioxy-4-methyl-1-naphthyl)propionic acid (EP-1), one of the derivatives, inhibited E. coli growth dose- and incubation temperature-dependently and caused E. coli lethality. Furthermore, EP-1 did not induce superoxide dismutase or catalase in E. coli even when the cells were incubated in nutritionally rich medium containing trypticase/soy/yeast extract. Singlet oxygen, one of the reactive oxygen species, did not act as a signal for induction of superoxide dismutase and catalase, in contrast to the actions of superoxide and hydrogen peroxide.