Leuconostoc mesenteroides and Leuconostoc pseudomesenteroides bacteriophages: Genomics and cross-species host ranges.

Unveiling virus-host interactions are relevant for understanding the biology and evolution of microbes globally, but in particular, it has also a paramount impact on the manufacture of fermented dairy products. In this study, we aim at characterizing phages infecting the commonly used heterofermentative Leuconostoc spp. on the basis of host range patterns and genome analysis. Host range of six Leuconostoc phages was investigated using three methods (efficiency of plaquing, spot and turbidity tests) against Ln. mesenteroides and Ln. pseudomesenteroides strains. Complete genome sequencing from four out of the six studied Leuconostoc phages were obtained in this work, while the remaining two have been sequenced previously. According to our results, cross-species host specificity was demonstrated, as all phages tested were capable of infecting both Ln. pseudomesenteroides and Ln. mesenteroides strains, although with different efficiency of plaquing (EOP). Phage adsorption rates and ability of low-EOP host strains to propagate phages by crossing the Leuconostoc species' barrier confirm results. At the genome level, phages CHA, CHB, Ln-7, Ln-8 and Ln-9 revealed high similarity with previously characterized phages infecting mostly Ln. mesenteroides strains, while phage LDG was highly similar to phages infecting Ln. pseudomesenteroides. Additionally, correlation between receptor binding protein (RBP) and host range patterns allowed us to unveil a finer clustering of Leuconostoc phages studied into four groups. This is the first report of overlapped phage host ranges between Leuconostoc species.