Insertional inactivation of the Staphylococcus aureusβ‐toxin by bacteriophage φ13 occurs by site‐and orientation‐specific integration of the φ 13 genome

Summary Lysogenization of Staphylococcus aureus by the sero-type F converting bacteriophage φ13 results in loss of β-toxin expression. Sequence analysis of the S. aureusβ-toxin gene (hlb), the attachment site (aftP)-containing region of φ 13 DNA and the chromosome/bacteriophage DNA junctions of a φ13 lysogen, revealed that the molecular mechanism of loss of βtoxin expression was due to insertion of the φ13 genome into the 5′ end of hlb. The insertion site (attB) within hlb contained a 14 base pair core sequence in common with attP and both ends of the integrated linear prophage genome of a φ 13 lysogen. These findings indicate that integration of the φ13 genome into hlb is site-and orientation-specific.