INSERTIONAL INACTIVATION OF THE STAPHYLOCOCCUS-AUREUS BETA-TOXIN BY BACTERIOPHAGE PHI-13 OCCURS BY SITE-SPECIFIC AND ORIENTATION-SPECIFIC INTEGRATION OF THE PHI-13 GENOME

Lysogenization of Staphylococcus aureus by the sero-type F converting bacteriophage phi-13 results in loss of beta-toxin expression. Sequence analysis of the S. aureus beta-toxin gene (hlb), the attachment site (attP)-containing region of phi-13 DNA and the chromosome/bacteriophage DNA junctions of a phi-13 lysogen, revealed that the molecular mechanism of loss of beta-toxin expression was due to insertion of the phi-13 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 phi-13 lysogen. These findings indicate that integration of the phi-13 genome into hlb is site- and orientation-specific.