CHARACTERIZATION OF A VIRULENT LACTOBACILLUS-SAKE PHAGE PWH2

A virulent bacteriophage PWH2 was isolated from fermented sausage. Out of 14 strains of Lactobacillus sake and 5 strains of L. curvatus test ed as potential hosts, only L. sake Ls2 was sensitive. The plaques had a diameter of 0.5-1 mm. One-step growth kinetics of bacteriophage PWH 2 revealed the following characteristics: a latent period of 1.5 h, a rise period of 1 h and a burst size of 110 (+/-10) phages per cell. Fr om electron micrographs it was deduced that bacteriophage PWH2 has an icosahedral head, a long non-contractile tail and a complex base plate . The genome is linear and 35 kbp in length. The structural proteins c onsist of three major and two minor proteins. After an infection of L. sake Ls2, isolates were obtained that were resistant to PWH2. By trea tment with mitomycin C, isolate R4a was found to be lysogenic. DNA/DNA hybridisation proved homology of phage PWH2 with the chromosomal DNA of strain R4a.