Mechanism of action of lactostrepcin 5, a bacteriocin produced by Streptococcus cremoris 202

The mechanism of bactericidal activity of lactostrepcin 5 (Las 5), a bacteriocin produced by Streptococcus cremoris 202, was investigated. Las 5 did not kill protoplasts of sensitive cells, and its activity was decreased about 10-fold after pretreatment of the cells with trypsin, suggesting the involvement of the cell wall in the activity of this bacteriocin. In susceptible cells, the bacteriocin slowed down and then stopped synthesis of DNA, RNA, and protein, although this did not appear to be the primary effect of Las 5 action. Las 5 also inhibited uridine transport in susceptible cells and induced leakage of K+ ions and ATP. Survival of cells treated with Las 5 in phosphate buffer was higher in the presence of K+, CA2+, or Mg2+ ions.