REVERSIBLE SPORICIDAL ACTION OF CUPROUS IONS

At 10 mM, Cu+ was highly protective against killing of spores of Bacil lus megaterium ATCC 19213 by H2O2, while at higher concentrations, fro m 15-100 mM, killing was augmented. In contrast, Cu2+, Fe2+, Fe3+, Co2 + Or Co3- ions acted only protectively. Cu+ itself was sporicidal in t he absence of H2O2 or ascorbate, and its sporicidal action did not dep end on generation of highly reactive oxygen species. It appeared that killing involved either inhibition of germination or copper toxicity t o germinated cells in that Cu+-inactivated spores did not germinate re adily but chemical decoating of the cells prior to plating on a solid medium resulted in reversal of the sporicidal effect.