Genome analysis of two virulent Streptococcus thermophilus phages isolated in Argentina

Instituto de Lactología Industrial (INLAIN, UNL-CONICET), Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santa Fe, Argentina.
International journal of food microbiology (Impact Factor: 3.08). 09/2009; 136(1):101-9. DOI: 10.1016/j.ijfoodmicro.2009.09.005
Source: PubMed


Two Streptococcus thermophilus phages (ALQ13.2 and phiAbc2) were previously isolated from breakdowns of cheese manufacture in Argentina. Complete nucleotide sequence analysis indicated that both phages contained linear double-stranded DNA: 35,525 bp in length for the pac-type phage ALQ13.2 and 34,882 bp for the cos-type phage phiAbc2. Forty-four and 48 open reading frames (ORF) were identified for ALQ13.2 and phiAbc2, respectively. Comparative genomic analysis showed that these isolates shared many similarities with the eight previously studied cos- and pac-phages infecting different S. thermophilus strains. In particular, part of the phiAbc2 genome was highly similar to a region of phage 7201, which was thought to be unique to this latter phage. Protein analysis of the pac-phage ALQ13.2 using SDS polyacrylamide gel electrophoresis (SDS-PAGE) identified three major proteins and seven minor proteins. Parallel structural proteome analysis of phiAbc2 revealed seven protein bands, two of which were related to major structural proteins, as expected for a cos-type phage. Similarities to other S. thermophilus phages suggest that the streptococcal phage diversity is not extensive in worldwide dairy factories possibly because related high-performing bacterial strains are used in starter cultures.

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    • "In contrast to the phages of L. lactis, all phages infecting S. thermophilus display a similar morphology with long, non-contractile tails (typically more than 200 nm in length) and isometric capsid structures, thus belonging to the Siphoviridae family (Brussow et al., 1994; Bruttin et al., 1997; Levesque et al., 2005; Guglielmotti et al., 2009; Zinno et al., 2010; Mills et al., 2011). Therefore, electron microscopy and associated morphological analysis provides little scope for differentiation between these phages, thus necessitating the application of other methods of discernment. "
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    • "Most isolated phages harbour the Sfi21-like replication module, which is unusually conserved (Desiere, Lucchini, Bruttin, Zwahlen, & Brussow, 1997). Up until now, phage 7201 and phage Abc2 were the only known S. thermophilus phages to contain the 7201-like DNA replication module (Guglielmotti et al., 2009). However, a comparison of the replication module of phage 5093 with the replication modules of phages Sfi21 and 7201 indicated that phage 5093 also harbours a 7201-type DNA replication module, sharing 79% identity over 2513 base pairs of the 7201-type region but showing no significant similarity to the corresponding region of Sfi21. "
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