Isolation and Characterization of Temperate and Virulent Bacteriophages of Lactobacillus plantarum

Several bacteriophages that are able to infect Lactobacillus plantarum have been isolated by induction of lysogenic strains with mitomycin C and by enrichment of samples from different origins. Two closely related phages (~LPI-A and ~LPI-B), isolated from com silage, and phage ~LP2, isolated from a homemade cheese whey, were characterized. Some features of L. plantarum phage lri were also studied that have not been previously published. Virions of the ~LPI and ~LP2 groups displayed a typical B1 morphology (Siphoviridae); heads were isometric, and tails were long and noncontractile. The genetic material of the virions was a single molecule of doublestranded DNA without cohesive ends. The genome lengths were 80 kbp (~LPI group), 47 kbp (~LP2), and 133 kbp (fri). Host range was limited to some strains of L. plantarum. Temperature of propagation affected the appearance and aspect of the plaques of lysis. Phage adsorption was quite efficient, reaching >90% in most cases and often >99%, and was not affected by the temperature. One-step growth experiments showed that, in some cases, temperature strongly influenced the phage development. The temperate nature of the phages could only be established for phage ~LP2, and no lysogens were obtained for members of the ~LPI group.