title: Site-specific spontaneous deletions in three genome regions of a temperate Streptococcus thermophilus phage.
abstract: Site-specific spontaneous deletions were observed with high frequency in three regions of the genome of the temperate Streptococcus thermophilus phage phi SFi21. Deletion sizes were 750 bp (type 1), 2.7 kb (type 2), and 1 kb (type 3). Combinations of types 1 and 3 and 2 and 3 were observed. The mutants grew lytically although with reduced burst sizes. Type 2 mutants lost the capacity to lysogenize host cells. Upon serial passage, the deletion mutants overgrew the wild-type phage. No direct or inverted DNA repeats were associated with type 1 or 2 deletion sites. Several independent phage isolates showed deletions at identical nucleotide positions, suggesting a site-specific recombination system. Sequencing of an Xbal restriction fragment covering the type 1 deletion predicted a single long open reading frame (ORF) showing a high degree of amino acid similarity with two proteins from bacteriophage P1 implicated in its immunity control (KiIA, Ant). Type 1 deletion leads to a loss of the conserved C-terminal part of this ORF.
authors.affiliation: Nestlé Research Centre, Lausanne, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Bruttin
authors.forename: H
authors.initials: H
authors.lastname: Brüssow
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D017931:DNA Primers; D004279:DNA, Viral; D016679:Genome, Viral; D008242:Lysogeny; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013291:Streptococcus / Q000821:virology; D017108:Streptococcus Phages / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification
chemical_list: D017931:DNA Primers; D004279:DNA, Viral