Diversity of Streptococcus thermophilus Phages in a Large-Production Cheese Factory in Argentina

Pulsed-field gel (PFG) electrophoresis patterns of phage-sensitive Streptococcus thermophilus strains. M = low-range PFG markers (New England BioLabs, Ipswich, MA).

Restriction profiles of the 10 Streptococcus thermophilus phages. EcoRI restriction profiles of the cos-type (A) and pac-type (B) phages; EcoRV restriction profiles of the cos-type (C) and pac-type (D) phages.

Electron micrograph of Streptococcus thermophilus phage ALQ1.3 isolated from whey cheese samples. Bar represents 30nm.

Multiplex PCR for the detection of the 2 groups of Streptococcus thermophilus phages. Nucleotide sequence alignments of the conserved regions used to design the primers for the cos-type (A) and the pac-type (B) phages. The genes coding for the major capsid protein were analyzed in 4 cos-type phages: phage Sfi19 (orf39, GenBank accession number AF115102), phage 7201 (mpl-7201, AF145054), phage DT1 (orf8, AF085222), and phage Sfi21 (orf9, AF115103). Similarly, the genes coding for the major capsid protein were analyzed in 3 pac-type phages: phage O1205 (orf31, U88974), phage Sfi11 (orf348, AF145054), and phage 2972 (orf9, AY699705). The corresponding coordinates are indicated on the left and right sides. (C) Classification of the 10 isolated S. thermophilus phages by the multiplex PCR. M = 100-bp DNA ladder (Invitrogen Life Technologies, Carlsbad, CA); CTRL = control.