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 rela ted phages (Phi LP1-A and Phi LP1-B), isolated from corn silage, and p hage 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 grou ps displayed a typical B1 morphology (Siphoviridae); heads were isomet ric, and tails were long and noncontractile. The genetic material of t he virions was a single molecule of double-stranded DNA without cohesi ve ends. The genome lengths were 80 kbp (Phi LP1 group), 47 kbp (Phi L P2), and 133 kbp (fri). Host range was limited to some strains of L. p lantarum. Temperature of propagation affected the appearance and aspec t of the plaques of lysis. Phage adsorption was quite efficient, reach ing >90% in most cases and often >99%, and was not affected by the tem perature. One-step growth experiments showed that, in some cases, temp erature strongly influenced the phage development. The temperate natur e of the phages could only be established for phage Phi LP2, and no ly sogens were obtained for members of the Phi LP1 group.