Comparative analysis of the genomes of the temperate bacteriophages φ11, φ12 and φ13 of Staphylococcusaureus 8325

Abstract

The genomes of the three temperate bacteriophages contained in the chromosome of Staphylococcusaureus 8325 have been extracted from the sequence database and analyzed. φ11, φ12 and φ13 are members of the same lytic group but different serogroups and consequently co-habitate the same host cell. Their genomes are approximately 42 kb to 45kb and contain about 90 ORFs of at least 50 codons. Of these, about 50 have similarities to known genes or to genes of other staphylococcal phages. Each of the phages clusters within a homology group that share large regions of sequence identity while intergroup homology is comparatively low. The arrangement of genes on the chromosomes of the three phages is similar and consistent with current modular theory of phage gene organization. The replicated genomes appear to be packaged by different mechanisms. Phage φ11 and φ12 have been found to contain sequences consistent with pac-site phages while φ13 has sequences consistent with cos-site phages. The attBsite for φ11 is located in an intergenic region of the S. aureus chromosome while φ12 and φ13 integrate into specific genes. The φ12 att-site is within an unknown gene, but the φ13 att-site is within the β-toxin gene. In contrast to the other two phages, φ13 also introduces the staphylokinase gene (sak) and a second gene related to expression of fib.