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 (Phi LP1-A and Phi LP1-B), isolated from corn silage, and phage Phi LP2, isolated from a homemade cheese whey, were characterized. Some features of L. plantarum phage fri were also studied that have not been previously published. Virions of the Phi LP1 and Phi 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 double-stranded DNA without cohesive ends. The genome lengths were 80 kbp (Phi LP1 group), 47 kbp (Phi 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 Phi LP2, and no lysogens were obtained for members of the Phi LP1 group.