Bactericidal effect of Fe 2+, ceruloplasmin, and phosphate

Abstract

Fe 2+, when combined with ceruloplasmin or phosphate, was bactericidal to Escherichia coli at pH 5.0, and when Fe 2+, ceruloplasmin, and phosphate were combined, a bactericidal effect was observed under conditions, i.e., short incubation period, in which Fe 2+ plus ceruloplasmin and Fe 2+ plus phosphate were ineffective. Bactericidal activity increased with the ceruloplasmin or phosphate concentration to a maximum and then decreased as their concentration was further increased. Fe 2+ was oxidized in the presence of ceruloplasmin, phosphate, or, in particular, a combination of the two. A bactericidal effect was observed when there was only a partial loss of Fe 2+, with more extensive oxidation resulting in a loss of bactericidal activity. The bactericidal effect of Fe 2+ plus ceruloplasmin and/or phosphate was unaffected by catalase or superoxide dismutase and was not associated with iodination. Fe-EDTA was also bactericidal at an Fe 2+: EDTA molar ratio of 1:0.5, where Fe 2+ was partially oxidized. However, in contrast to Fe 2+ plus ceruloplasmin and/or phosphate, bactericidal activity was inhibited by catalase and was associated with iodination. Combinations of Fe 2+ and Fe 3+ were not bactericidal under the conditions employed. A requirement for Fe 2+ plus either a product of Fe 2+ oxidation or an iron ceruloplasmin and/ or phosphate chelate for bactericidal activity is proposed.