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.
Eighty-seven strains of lactic streptococci (46 of Streptococcus lactis, 24 of S. diacetilactis, and 17 of S. cremoris) were tested for lysogeny; 12 S. lactis strains produced nisin. Lysogeny was found in five S. lactis strains (two of them were nisin producers) and in two S. diacetilactis strains. Four S. lactis and two S. diacetilactis lysogens liberated phages both spontaneously and after ultraviolet treatment, and one S. lactis strain liberated phages spontaneously only. No lysogens were found among the S. cremoris strains tested. An initial characterization of the lysogens and their phages was made. The lytic spectrum of some of the examined phages was very narrow (homospecific), whereas that of others was wide, including strains of the three investigated species.
Eighty-seven strains of lactic streptococci (46 of
Streptococcus lactis
, 24 of
S. diacetilactis
, and 17 of
S. cremoris
) were tested for lysogeny; 12
S. lactis
strains produced nisin. Lysogeny was found in five
S. lactis
strains (two of them were nisin producers) and in two
S. diacetilactis
strains. Four
S. lactis
and two
S. diacetilactis
lysogens liberated phages both spontaneously and after ultraviolet treatment, and one
S. lactis
strain liberated phages spontaneously only. No lysogens were found among the
S. cremoris
strains tested. An initial characterization of the lysogens and their phages was made. The lytic spectrum of some of the examined phages was very narrow (homospecific), whereas that of others was wide, including strains of the three investigated species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.