Abstract
ABSTRACTBacteriophages are the main cause of fermentation failures in dairy plants. The majority of Streptococcus thermophilus phages can be divided into either cos- or pac-type phages and are additionally characterized by examining the V2 region of their antireceptors. We screened a large number of S. thermophilus phages from the Chr. Hansen A/S collection, using PCR specific for the cos- or pac-type phages, as well as for the V2 antireceptor region. Three phages did not produce positive results with the assays. Analysis of phage morphologies indicated that two of these phages, CHPC577 and CHPC926, had shorter tails than the traditional S. thermophilus phages. The third phage, CHPC1151, had a tail size similar to those of the cos- or pac-type phages, but it displayed a different baseplate structure. Sequencing analysis revealed the genetic similarity of CHPC577 and CHPC926 with a subgroup of Lactococcus lactis P335 phages. Phage CHPC1151 was closely related to the atypical S. thermophilus phage 5093, homologous with a nondairy streptococcal prophage. By testing adsorption of the related streptococcal and lactococcal phages to the surface of S. thermophilus and L. lactis strains, we revealed the possibility of cross-interactions. Our data indicated that the use of S. thermophilus together with L. lactis, extensively applied for dairy fermentations, triggered the recombination between phages infecting different bacterial species. A notable diversity among S. thermophilus phage populations requires that a new classification of the group be proposed.IMPORTANCE Streptococcus thermophilus is a component of thermophilic starter cultures commonly used for cheese and yogurt production. Characterizing streptococcal phages, understanding their genetic relationships, and studying their interactions with various hosts are the necessary steps for preventing and controlling phage attacks that occur during dairy fermentations.
Highlights
IMPORTANCE Streptococcus thermophilus is a component of thermophilic starter cultures commonly used for cheese and yogurt production
Almost all known S. thermophilus phages show similar overall characteristics, displaying double-stranded DNA packed into an isometric capsid (45 to 60 nm in diameter) connected to a long noncontractile tail (200 to 260 nm in length). They belong to the Siphoviridae family of the Caudovirales order [2, 3]. In addition to their morphological similarity, many S. thermophilus phages seem to be homologous on a genetic level
The results of this study showed that S. thermophilus phages are likely to inherit structural genetic modules from various phages of dairy and nondairy species
Summary
IMPORTANCE Streptococcus thermophilus is a component of thermophilic starter cultures commonly used for cheese and yogurt production. Almost all known S. thermophilus phages show similar overall characteristics, displaying double-stranded DNA (genome size, 30 kb to 45 kb) packed into an isometric capsid (45 to 60 nm in diameter) connected to a long noncontractile tail (200 to 260 nm in length) They belong to the Siphoviridae family of the Caudovirales order [2, 3]. The most used grouping distinguishes two subgroups, the cos- or pac-type phages, correlating the DNA packaging mechanism with a set of two or three major structural proteins, respectively [5]. Another important grouping is based on the variable region VR2 of the antireceptor gene of S. thermophilus phages. This method enables linking of the detected phage with its host specificity [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
