Inactivation of a Streptococcal Bacteriocin (Viridin B) by Mammalian Hemoglobin

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Abstract
Viridin B, a bacteriocin of Streptococcus mitis (S. mitior), had no bactericidal effect on indicator strains grown on blood agar, whereas activity was readily demonstrable on the same agar devoid of blood. Addition of viridin B to human, ovine, bovine or rabbit erythrocytes caused immediate lysis of the cells and total inactivation of the bacteriocin. Inactivation was effected also by erythrocyte lysates. Activity in the lysates was heat resistant, nondialyzable and insensitive to proteolytic enzymes. Chromatography on a Bio-Rad P-100 column indicated that the inhibitory activity resided exclusively in hemoglobin. Fractionation of hemoglobin showed that heme and not globin was totally responsible for this inactivation. The effect of heme appeared to be directly on viridin B rather than on blockage of indicator cell receptors. Cytochrome c, bilirubin, and ferrous and ferric ions had no effect on the bacteriocin. Among various other ions tested, only Ca2+ inhibited viridin B. Urea was also inhibitory but only in high concentrations.

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