Classification of Lytic Bacteriophages Attacking Dairy Leuconostoc Starter Strains

Abstract

A set of 83 lytic dairy bacteriophages (phages) infecting flavor-producing mesophilic starter strains of the Leuconostoc genus was characterized, and the first in-depth taxonomic scheme was established for this phage group. Phages were obtained from different sources, i.e., from dairy samples originating from 11 German dairies (50 Leuconostoc pseudomesenteroides [Ln. pseudomesenteroides] phages, 4 Ln. mesenteroides phages) and from 3 external phage collections (17 Ln. pseudomesenteroides phages, 12 Ln. mesenteroides phages). All phages belonged to the Siphoviridae family of phages with isometric heads (diameter, 55 nm) and noncontractile tails (length, 140 nm). With the exception of one phage (i.e., phage ⌽LN25), all Ln. mesenteroides phages lysed the same host strains and revealed characteristic globular baseplate appendages. Phage ⌽LN25, with different Y-shaped appendages, had a unique host range. Apart from two phages (i.e., phages P792 and P793), all Ln. pseudomesenteroides phages shared the same host range and had plain baseplates without distinguishable appendages. They were further characterized by the presence or absence of a collar below the phage head or by unique tails with straight striations. Phages P792 and P793 with characteristic fluffy baseplate appendages could propagate only on other specific hosts. All Ln. mesenteroides and all Ln. pseudomesenteroides phages were members of two (host species-specific) distinct genotypes but shared a limited conserved DNA region specifying their structural genes. A PCR detection system was established and was shown to be reliable for the detection of all Leuconostoc phage types.

Isolation and characterisation of novel phages infectingLactobacillus plantarumand proposal of a new genus, “Silenusvirus”

“…Similar flexible globular structures and capsid-tail dimensions have been observed for other Lactobacillus phages but their exact role remains unknown 3,40 . Interestingly, in some Leuconostoc mesenteroides phages similar baseplate appendages could also adsorb to other parts of the tail in an inconsistent manner 41 . These characteristics classify Silenus to the order Caudovirales and the family Siphoviridae ( Fig.…”

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

“…Previous studies carried out on the RPB genes of two Ln. pseudomesenteroides phages, ɸLN04 (ORF23) and P793 (ORF21), which present nonoverlapping host ranges, demonstrated that the deduced putative proteins from these ORFs could be divided into two fragments (Kot et al, 2013). Only the first amino acid portion (N-terminal) shows similarity (75 % nucleotide identity), while the C-terminal part did not show any significant similarity between each other.…”

“…mesenteroides strains have been reported to be unable to infect Ln. pseudomesenteroides strains and vice versa (Ali et al, 2013;Kot et al, 2014).…”

A high-throughput qPCR system for simultaneous quantitative detection of dairy Lactococcus lactis and Leuconostoc bacteriophages

“…mesenteroides and II infecting Le . pseudomesenteroides [16]. With the exception of one temperate phage (φMH1) [17], all Leuconostoc phages identified so far are lytic phages.…”

“…The universal PCR detection system designed by Ali et al . allowed qualitative detection of dairy Leuconostoc phages [16]. Increasing demands for quantitative, more sensitive, rapid and real-time monitoring of specific phages during the fermentation process has prompted the development of real-time quantitative PCR (qPCR) methods.…”