Streptococcus thermophilus bacteriophages

Streptococcus salivarius is an abundant isolate of the oral cavity. The genome of S. salivarius 57.I consists of a 2-Mb chromosome and a 40,758-bp circular molecule, designated YMC-2011. Annotation of YMC-2011 revealed 55 open reading frames, most of them associated with phage production, although plaque formation is not observed in S. salivarius 57.I after lytic induction using mitomycin C. Results from Southern hybridization and quantitative real-time PCR confirmed that YMC-2011 exists extrachromosomally, with an estimated copy number of 3 to 4. Phage particles were isolated from the supernatant of mitomycin C-treated S. salivarius 57.I cultures, and transmission electron microscopic examination indicated that YMC-2011 belongs to the Siphoviridae family. Phylogenetic analysis suggests that phage YMC-2011 and the cos-type phages of Streptococcus thermophilus originated from a common ancestor. An extended Ϫ10 element (p L ) and a 70 -like promoter (p R ) were mapped 5= to Ssal_phage00013 (encoding a CI-like repressor) and Ssal_phage00014 (encoding a hypothetical protein), respectively, using 5= rapid amplification of cDNA ends, indicating that YMC-2011 transcribes at least two mRNAs in opposite orientations. Studies using promoter-chloramphenicol acetyltransferase reporter gene fusions revealed that p R , but not p L , was sensitive to mitomycin C induction, suggesting that the switch from lysogenic growth to lytic growth was controlled mainly by the activity of these two promoters. In conclusion, a lysogenic state is maintained in S. salivarius 57.I, presumably by the repression of genes encoding proteins for lytic growth.IMPORTANCE The movement of mobile genetic elements such as bacteriophages and the establishment of lysogens may have profound effects on the balance of microbial ecology where lysogenic bacteria reside. The discovery of phage YMC-2011 from Streptococcus salivarius 57.I suggests that YMC-2011 and Streptococcus thermophilus-infecting phages share an ancestor. Although S. salivarius and S. thermophilus are close phylogenetically, S. salivarius is a natural inhabitant of the human mouth, whereas S. thermophilus is commonly found in the mammary mucosa of bovine species. Thus, the identification of YMC-2011 suggests that horizontal gene transfer via phage infection could take place between species from different ecological niches.KEYWORDS Streptococcus salivarius, temperate phage, lysogeny, plasmid, Siphoviridae family P hages, prokaryotic viruses, are the most abundant biological entities on the planet (1). Although phages have been isolated from the oral cavity (2, 3), relatively little is known about the phages of oral streptococci, compared to those of other lactic acid bacteria, particularly Lactococcus lactis and Streptococcus thermophilus. To date, the better characterized phages of oral streptococci are the virulent phage M102AD of Streptococcus mutans (4) and the temperate phage SM1 of Streptococcus mitis (5). A Streptococcus salivarius-infecting phage of the family Cystoviridae wa...

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confidence: 96%

YMC-2011, a Temperate Phage of Streptococcus salivarius 57.I

Chou

Huang

Chiu

et al. 2017

“…Bacteriophages infecting L. lactis and Streptococcus thermophilus cultures have been studied extensively (12)(13)(14), while only limited knowledge exists for dairy Leuconostoc phages. Since Leuconostoc strains do not contribute significantly to lactic acid production in milk, phage infections of Leuconostoc cultures may remain unnoticed during processing but will be detected in the final products.…”

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confidence: 99%

Classification of Lytic Bacteriophages Attacking Dairy Leuconostoc Starter Strains

Ali

Kot

Atamer

et al. 2013

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.

“…Other investigators previously reported a larger capsid diameter (110 nm) and a much longer tail (500 nm) for L. plantarum phage B2 (54). Although dimensions may vary due to the use of different electron microscopes and methodologies (59), this cannot explain such large differences. At this time, it is unclear why such a discrepancy exists.…”

Section: Methodsmentioning

confidence: 86%

Characterization of Two Virulent Phages of Lactobacillus plantarum

Marcó

Garneau

Tremblay

et al. 2012

Self Cite

We characterized two Lactobacillus plantarum virulent siphophages, ATCC 8014-B1 (B1) and ATCC 8014-B2 (B2), previously isolated from corn silage and anaerobic sewage sludge, respectively. Phage B2 infected two of the eight L. plantarum strains tested, while phage B1 infected three. Phage adsorption was highly variable depending on the strain used. Phage defense systems were found in at least two L. plantarum strains, LMG9211 and WCSF1. The linear double-stranded DNA genome of the pac-type phage B1 had 38,002 bp, a G؉C content of 47.6%, and 60 open reading frames (ORFs). Surprisingly, the phage B1 genome has 97% identity with that of Pediococcus damnosus phage clP1 and 77% identity with that of L. plantarum phage JL-1; these phages were isolated from sewage and cucumber fermentation, respectively. The double-stranded DNA (dsDNA) genome of the cos-type phage B2 had 80,618 bp, a G؉C content of 36.9%, and 127 ORFs with similarities to those of Bacillus and Lactobacillus strains as well as phages. Some phage B2 genes were similar to ORFs from L. plantarum phage LP65 of the Myoviridae family. Additionally, 6 tRNAs were found in the phage B2 genome. Protein analysis revealed 13 (phage B1) and 9 (phage B2) structural proteins. To our knowledge, this is the first report describing such high identity between phage genomes infecting different genera of lactic acid bacteria.