Incidence of Lysogeny in Wild Lactococcal Strains

Abstract

The incidence of lysogeny among 172 lactococcal strains, isolated from natural dairy fermentations and selected by their high capacity to coagulate milk and to produce lactic acid, was studied. Lysis of 92 strains (53% of the strains tested) was observed after using mitomycin C for induction of cultures. Fifty-one of these 92 strains released phages that were able to propagate on indicator strains. Twenty-eight (16%) of the 172 strains tested acted as host for at least one phage, although some supported the development of more than one phage isolate. Spontaneous induction was insignificant in >50% of strains inducible by mitomycin C, but titers after mitomycin C induction varied between 101 and l06 pfu/ml. No plaque formation was observed at 37°C. The bacteriophages belonged to the family Siphoviridae, as revealed by electron microscopy. Head and tail dimensions ranged widely. Some temperate phages that were unable to form plaques of lysis appeared to be defective viral particles. © 1995, American Dairy Science Association. All rights reserved.