Novel Phage Group Infecting Lactobacillus delbrueckii subsp lactis, as Revealed by Genomic and Proteomic Analysis of Bacteriophage Ldl1

Abstract

Ldl1 is a virulent phage infecting the dairy starter Lactobacillus delbrueckii subsp. lactis LdlS. Electron microscopy analysis revealed that this phage exhibits a large head and long tail, and bears little resemblance to other characterized phages infecting Lactobacillus delbrueckii. In vitro propagation of this phage revealed a latent period of 30 - 40 mins and a burst size of 59.9 ± 1.9. Comparative genomic and proteome analyses showed remarkable similarity between the genome of Ldl1 and that of Lactobacillus plantarum phage ATCC8014-B2. The genomic and proteomic characteristics of Ldl1 demonstrate that this phage does not belong to any of the four previously recognized Lb. delbrueckii phage groups, necessitating the creation of a new group, called group e, thus adding to the knowledge on diversity of phages targeting strains of this industrially important lactic acid bacterial species.