Ultrastructural and biochemical alterations effected by viridin B, a bacterocin of alpha-hemolytic streptococci.

Viridin B, a bacteriocin produced by Streptococcus mitis strain 42885, was shown previously to exert a bactericidal effect against a Neisseria sicca strain but only a bacteriostatic effect against a coagulase-negative staphylococcus. In the present report, this dual effect was defined further. Viridin B caused the appearance of mesosomes in both indicator strains early in the course of exposure. Whereas mesosomes were the only noticeable alterations in the staphylococcal strain at all times of exposure to bacteriocin, progressive changes occurred in the N. sicca cells involving the nucleoid and cytoplasmic contents and resulting in the appearance of bacterial ghosts. Biochemical studies indicated a rapid and complete cessation of the incorporation of [3H]thymidine in N. sicca and in the staphylococcus. Whereas the incorporation of [3H]leucine and [3H]uridine in N. sicca was completely stopped, such incorporation was only reduced in the staphylococcus.