Characterization of two virulent Lactobacillus fermentum bacteriophages isolated from sour dough

Two different bacteriophages, FE5-B1 and Z63-B1, active against strains of Lactobacillus fermentum were isolated from a sample of sour dough of a regional wheat bread. They showed different host specificities when tested against 58 strains of obligately heterofermentative lactic acid bacteria, as well as differences in adsorption and one-step growth kinetics. The burst size of FE5-B1 was about 100 pfu cell(-1). This phage belonged to the A(1) morphotype of Myoviridae family, having an icosahedral head (83 nm diam.) and a sheathed contractile tail (170 nm in length). The phage consisted of five major structural proteins and had a genome of 86 kbp. Z63-B1 showed a burst size of 10 pfu cell(-1) and belonged to the B-1 morphotype or Siphoviridae family. Z63-B1 had an isometric head (60 nm diam.) and a non-contractile tail (160 nm in length), with eight major different structural proteins and a genome of 32 kbp.