Characterization and comparison of virulent bacteriophages of Streptococcus thermophilus isolated from yogurt.
Seven virulent bacteriophages of Streptococcus thermophilus were characterized at the molecular level and classified into 2 subgroups (A and B) by DNA/DNA hybridization experiments and analysis of their structural proteins. Two representatives of subgroups A and B were compared to 3 representatives of Neve's subgroups I, II and III (Neve et al, 1989) by Southern blot experiments. These isometric-headed phages possess a double-stranded DNA genome varying between 30-44 kilobase (kb) pairs. Subgroup A is composed of 3 phages (phi 57 as representative) with similar structural proteins as determined by sodium dodecyl sulfate-poly-acrylamide gel (SDS-PAGE) electrophoresis (estimated molecular weights of 31,000 and 27,500 for phage phi 57 and 32,000 and 27,000 for the 2 others). A common structural protein of 43,000 was found for phages of subgroup B. Phages phi 57 (subgroup A) and a10/J9 or PO (Neve's subgroups I or II, respectively) belonged to the same subgroup as determined by DNA/DNA hybridization experiments. Partial DNA homology was detected among all the phages tested except for phage phi ST27 of AW Jarvis. Phage-host interactions were also investigated by cross-propagation of the 7 studied phages on different indicator strains. A complete lack of correlation existed between the DNA homology grouping of the phages and their host range. Various restriction-modification systems were detected in some of the Streptococcus thermophilus strains.
Benbadis
L
L
Centre International de Recherche Daniel Carasso, Le Plessis-Robinson, France.
Faelen
M
M
Slos
P
P
Fazel
A
A
Mercenier
A
A
D001435:Bacteriophages / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D004279:DNA, Viral / Q000235:genetics; D005285:Fermentation; D005516:Food Microbiology; D008854:Microscopy, Electron; D009693:Nucleic Acid Hybridization; D012689:Sequence Homology, Nucleic Acid; D013291:Streptococcus; D015678:Viral Structural Proteins / Q000302:isolation & purification; D014774:Virulence; D015014:Yogurt
D004279:DNA, Viral; D015678:Viral Structural Proteins