Lactic acid bacteria (LAB) are economically important group of microbes used as starter cultures in the dairy industry. Bacteriophages attacking LAB are the main factor responsible for fermentations failures, thus creating significant economical losses worldwide.
In the first part of this study, bacteriophages infecting Leuconostoc species were characterized. A large group of Leuconostoc phages was characterized regarding the morphology, host range variation and genetic relatedness. A classification system for dairy Leuconostoc phages was proposed. dditionally, a PCR test for the dairy Leuconostoc phages was developed and tested.
The complete genomic DNA sequences of nine Leuconostoc phages were determined. The genomic sequences were analyzed with a focus on the gene content, gene organization and comparative genomics. Sequenced phages of Leuconostoc could be classified into two groups, which corresponds with the species of the host. The two groups shared overall genomic organization but differed significantly on the nucleotide level.
One of the specific genes, presumably coding for the receptor binding protein (RBP) in Leuconostoc pseudomesenteroides phages, was functionally characterized. In order to prove its biological function a chimeric phage with altered host range was generated. Obtained results demonstrated that ORF23"LN04 and ORF21P793 code for the RBP in Leuconostoc pseudomesenteroides phages.Characterization of phage-host interaction in the lactococcal 936 phages was performed.
The study was mainly focused on the interaction between the host cell wall
polysaccharides (CWPS) and the phage RBP. The results of the study suggest that both CWPS types and RBP determinants could be classified in groups, which correlated with each other.