MOLECULAR EVIDENCE FOR LYSOGENY IN LACTOBACILLUS-ACIDOPHILUS AND CHARACTERIZATION OF A TEMPERATE BACTERIOPHAGE

Thirty-five strains of Lactobacillus acidophilus were examined for the presence of inducible bacteriophage. Treatment of L. acidophilus CFM11, CFM12, and CFM13 with .12 μg/ml mitomycin C resulted in inductive lysis. Lysates contained structurally complete phage particles with isometric heads and long concentrically banded tails. Phage lysates exhibited no activity against 31 strains of L. acidophilus and 9 strains of eight additional Lactobacillus species. Thirty putative phage-free variants of L. acidophilus CFM11 were obtained. Lysates containing phage la11 inhibited all variants but did not plaque on any of them. The genome of temperate phage la11 showed homology with the genomes of the parental strain, L. acidophilus CFM11, and 20 noninducible variants but not those of five prophage-cured variants. The buoyant density of phage la11 was 1.43 g/cm3. Treatment of the phage la11 genome with restriction endonucleases indicated that it was double stranded DNA. Agarose gel electrophoresis of uncut and restricted la11 DNA indicated a molecular size of 45 to 48 kb. © 1990, American Dairy Science Association. All rights reserved.