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.

Mouse sperm basic nuclear protein. Electrophoretic characterization and fate after fertilization.

Mouse sperm were labeled in vivo with [3H]arginine. The sperm were then followed autoradiographically from the time of label incorporation until after fertilization. The label was completely lost from the sperm head after fertilization, during the oocyte's second meiotic division. That the [3H]arginine was incorporated into a sperm-specific basic protein was demonstrated by fractionating acid extracts of epididymal and ejaculated sperm with polyacrylamide gel electrophoresis. All the histone fractions were resolved in the epididymal extracts, but in addition a band was present that migrated faster than histone F2al and slower than the salmon protamine used as a marker. This new fraction (proposed name: musculine) was also present in ejaculated sperm; it was shown to be the only fraction that was labeled. Musculine therefore represents the end product of a histone transition in mice. It is, however, according to our electrophoretic characterization, not identical to the classical fish protamines. Rather, musculine resembles bovine sperm nuclear protein. Since the loss of this fraction from the sperm head was coincident with the rearrangement of the male genome, before its resumption of transcription, it is suggested that musculine is involved in the control of chromatin that accompanies spermiogenesis and fertilization.