Novel organization of the site‐specific integration and excision recombination functions of the Staphylococcus aureus serotype F virulence‐converting phages φ13 and φ42

Abstract

Functions required for site-specific integration and excision of the Staphylococcus aureus serotype F virulence-converting phages phi 13 and phi 42 were localized and characterized. Like other temperate phages, integration of phi 13 and phi 42 sequences was found to require the product of an int gene located close to the phage attP site. Both int genes are almost identical, express proteins possessing characteristic features of the Int (integrase) family of recombinases, but share very little homology with previously described int genes, including those of the serotype B S. aureus phages L54a and phi 11. Nevertheless, all four S. aureus phages share an almost identical short sequence located immediately 5' to these distinct int genes, suggesting a common mechanism of int gene regulation. Upstream from these common sequences, the sequences of phi 13 and phi 42 are quite distinct from each other, and from the corresponding regions of phi 11 and L54a which encode the Xis proteins that are required with Int to mediate site-specific excision of the latter phages. Surprisingly, phi 13 and phi 42 sequences encompassing the attP sites and int genes, but lacking either an adjacent or more distant phage excision protein gene, were sufficient to mediate site-specific excision of integrated phage DNA sequences.

Characterization and Expression Analysis of Staphylococcus aureus Pathogenicity Island 3

“…1. The placement of these structures is consistent with those genes that are known or likely to be independently transcribed, such as seb, sapi3_1 (ear), sek, and int, as well as with those genes that may well be co-transcribed, such as sapi3_14- 18.…”

Emergence of Hospital- and Community-Associated Panton-Valentine Leukocidin-Positive Methicillin-Resistant Staphylococcus aureus Genotype ST772-MRSA-V in Ireland and Detailed Investigation of an ST772-MRSA-V Cluster in a Neonatal Intensive Care Unit

“…The absence of DNA microarray signals corresponding to the presence of either the disrupted or complete beta-hemolysin gene hlb in the ST772-MRSA-V isolates in this and previous studies (24,34) is interesting. Most human S. aureus isolates, including MRSA, harbor a disrupted hlb gene due to insertional inactivation during lysogenization by hlb-converting bacteriophages (8,9). These findings indicate the possible presence of mutations in the primer or probe binding sites within hlb used with the DNA microarray system in isolates of this strain.…”

Prophage Genomics

“…phi11 is one of the few prophages from low-GϩC gram-positive bacteria that showed the attPint-xis gene constellation familiar from phage lambda (227,228). This is, however, not the common situation even in staphylococcal phages (38). phi13 was the first staphylococcal phage associated with positive (staphylokinase) and negative (betatoxin) phage conversion (222).…”