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Phage-mediated horizontal transfer of a Staphylococcus aureus virulence-associated genomic island.

Moon BY, Park JY, Hwang SY, Robinson DA, Thomas JC, Fitzgerald JR, Park YH, Seo KS - Sci Rep (2015)

Bottom Line: The genomic islands νSaα and νSaβ are found in almost all S. aureus strains and are characterized by extensive variation in virulence gene content.The transfer of the νSaβ appears to have been accomplished by multiple conversions of transducing phage particles carrying overlapping segments of the νSaβ.Our findings solve a long-standing mystery regarding the diversification and spread of the genomic island νSaβ, highlighting the central role of bacteriophages in the pathogenic evolution of S. aureus.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi state, MS 39762, United States [2] Department of Microbiology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul 151-742, South Korea.

ABSTRACT
Staphylococcus aureus is a major pathogen of humans and animals. The capacity of S. aureus to adapt to different host species and tissue types is strongly influenced by the acquisition of mobile genetic elements encoding determinants involved in niche adaptation. The genomic islands νSaα and νSaβ are found in almost all S. aureus strains and are characterized by extensive variation in virulence gene content. However the basis for the diversity and the mechanism underlying mobilization of the genomic islands between strains are unexplained. Here, we demonstrated that the genomic island, νSaβ, encoding an array of virulence factors including staphylococcal superantigens, proteases, and leukotoxins, in addition to bacteriocins, was transferrable in vitro to human and animal strains of multiple S. aureus clones via a resident prophage. The transfer of the νSaβ appears to have been accomplished by multiple conversions of transducing phage particles carrying overlapping segments of the νSaβ. Our findings solve a long-standing mystery regarding the diversification and spread of the genomic island νSaβ, highlighting the central role of bacteriophages in the pathogenic evolution of S. aureus.

No MeSH data available.


Related in: MedlinePlus

Proposed model for transfer of νSaβ mediated by φSaBov.Upon induction by mitomycin C, phage DNA (φSaBovN, φSaBovEGC, and φSaBovLUK) were excised from the RF122 chromosomal DNA and packed into phage head by terminase encoded in φSaBov. Upon entry to recipient strains, φSaBovN phage DNA is firstly integrated into recipient host chromosomal DNA through recombination between attNP (from φSaBovN) and attNR (recipient chromosomal DNA). This event introduces the attEGCR in recipient chromosomal DNA which allows φSaBovEGC phage DNA for integrating into recipient chromosomal DNA through recombination between attEGCP (from φSaBovEGC) and attEGCR (recipient chromosomal DNA). This event generates duplication of phage DNA. Homologous recombination occurs between φSaBovLUK phage DNA and integrated phage DNA, resulting removal of duplicated phage DNA. As a result of triple conversions, nearly all of the νSaβ from the donor strain is transferred to the recipient strain.
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f3: Proposed model for transfer of νSaβ mediated by φSaBov.Upon induction by mitomycin C, phage DNA (φSaBovN, φSaBovEGC, and φSaBovLUK) were excised from the RF122 chromosomal DNA and packed into phage head by terminase encoded in φSaBov. Upon entry to recipient strains, φSaBovN phage DNA is firstly integrated into recipient host chromosomal DNA through recombination between attNP (from φSaBovN) and attNR (recipient chromosomal DNA). This event introduces the attEGCR in recipient chromosomal DNA which allows φSaBovEGC phage DNA for integrating into recipient chromosomal DNA through recombination between attEGCP (from φSaBovEGC) and attEGCR (recipient chromosomal DNA). This event generates duplication of phage DNA. Homologous recombination occurs between φSaBovLUK phage DNA and integrated phage DNA, resulting removal of duplicated phage DNA. As a result of triple conversions, nearly all of the νSaβ from the donor strain is transferred to the recipient strain.

Mentions: Considering these data, we postulate the following νSaβ transduction model (Fig. 3). φSaBovN is firstly integrated into the attNR sequence at the tRNA-Ser which introduces the attEGCR site upstream of the int gene. Then, φSaBovEGC is integrated into the attEGCR, resulting in the transfer of the egc and the duplication of the region spanning between attNL and attEGCR. Homologous recombination events occur upstream of the SAB1676 gene, and downstream of attEGCR with the linear phage DNA introduced by φSaBovLUK, resulting in the removal of the duplicating region spanning between attNL and attEGCR and the replacement of the region spanning the lukE gene, similar to Panton-Valentine leukocidin-phage mediated homologous recombination events between direct repeats of the two paralogous genes adjacent to the phage integration site19. As a result, nearly all of the νSaβ (from the 141 bp upstream of the start codon of SAB1676 gene to the attNR sequence at the tRNA-Ser, a size of 65,767 bp) from strain RF122 was transferred to the recipient. Supporting this model, we were able to isolate transductant strains carrying intermediated forms of transduction carrying the φSaBovN at tRNA cluster and the φSaBovEGC at attEGCR without homologous recombination of the φSaBovLUK using a junction PCR as shown in Supplemental Figure S6. Furthermore, transductant strains carrying the φSaBovN or both φSaBovN and φSaBovEGC exhibited an increased capacity to accept the φSaBovEGC or the φSaBovLUK, respectively, as shown in supplemental Table S3.


Phage-mediated horizontal transfer of a Staphylococcus aureus virulence-associated genomic island.

Moon BY, Park JY, Hwang SY, Robinson DA, Thomas JC, Fitzgerald JR, Park YH, Seo KS - Sci Rep (2015)

Proposed model for transfer of νSaβ mediated by φSaBov.Upon induction by mitomycin C, phage DNA (φSaBovN, φSaBovEGC, and φSaBovLUK) were excised from the RF122 chromosomal DNA and packed into phage head by terminase encoded in φSaBov. Upon entry to recipient strains, φSaBovN phage DNA is firstly integrated into recipient host chromosomal DNA through recombination between attNP (from φSaBovN) and attNR (recipient chromosomal DNA). This event introduces the attEGCR in recipient chromosomal DNA which allows φSaBovEGC phage DNA for integrating into recipient chromosomal DNA through recombination between attEGCP (from φSaBovEGC) and attEGCR (recipient chromosomal DNA). This event generates duplication of phage DNA. Homologous recombination occurs between φSaBovLUK phage DNA and integrated phage DNA, resulting removal of duplicated phage DNA. As a result of triple conversions, nearly all of the νSaβ from the donor strain is transferred to the recipient strain.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4402969&req=5

f3: Proposed model for transfer of νSaβ mediated by φSaBov.Upon induction by mitomycin C, phage DNA (φSaBovN, φSaBovEGC, and φSaBovLUK) were excised from the RF122 chromosomal DNA and packed into phage head by terminase encoded in φSaBov. Upon entry to recipient strains, φSaBovN phage DNA is firstly integrated into recipient host chromosomal DNA through recombination between attNP (from φSaBovN) and attNR (recipient chromosomal DNA). This event introduces the attEGCR in recipient chromosomal DNA which allows φSaBovEGC phage DNA for integrating into recipient chromosomal DNA through recombination between attEGCP (from φSaBovEGC) and attEGCR (recipient chromosomal DNA). This event generates duplication of phage DNA. Homologous recombination occurs between φSaBovLUK phage DNA and integrated phage DNA, resulting removal of duplicated phage DNA. As a result of triple conversions, nearly all of the νSaβ from the donor strain is transferred to the recipient strain.
Mentions: Considering these data, we postulate the following νSaβ transduction model (Fig. 3). φSaBovN is firstly integrated into the attNR sequence at the tRNA-Ser which introduces the attEGCR site upstream of the int gene. Then, φSaBovEGC is integrated into the attEGCR, resulting in the transfer of the egc and the duplication of the region spanning between attNL and attEGCR. Homologous recombination events occur upstream of the SAB1676 gene, and downstream of attEGCR with the linear phage DNA introduced by φSaBovLUK, resulting in the removal of the duplicating region spanning between attNL and attEGCR and the replacement of the region spanning the lukE gene, similar to Panton-Valentine leukocidin-phage mediated homologous recombination events between direct repeats of the two paralogous genes adjacent to the phage integration site19. As a result, nearly all of the νSaβ (from the 141 bp upstream of the start codon of SAB1676 gene to the attNR sequence at the tRNA-Ser, a size of 65,767 bp) from strain RF122 was transferred to the recipient. Supporting this model, we were able to isolate transductant strains carrying intermediated forms of transduction carrying the φSaBovN at tRNA cluster and the φSaBovEGC at attEGCR without homologous recombination of the φSaBovLUK using a junction PCR as shown in Supplemental Figure S6. Furthermore, transductant strains carrying the φSaBovN or both φSaBovN and φSaBovEGC exhibited an increased capacity to accept the φSaBovEGC or the φSaBovLUK, respectively, as shown in supplemental Table S3.

Bottom Line: The genomic islands νSaα and νSaβ are found in almost all S. aureus strains and are characterized by extensive variation in virulence gene content.The transfer of the νSaβ appears to have been accomplished by multiple conversions of transducing phage particles carrying overlapping segments of the νSaβ.Our findings solve a long-standing mystery regarding the diversification and spread of the genomic island νSaβ, highlighting the central role of bacteriophages in the pathogenic evolution of S. aureus.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi state, MS 39762, United States [2] Department of Microbiology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul 151-742, South Korea.

ABSTRACT
Staphylococcus aureus is a major pathogen of humans and animals. The capacity of S. aureus to adapt to different host species and tissue types is strongly influenced by the acquisition of mobile genetic elements encoding determinants involved in niche adaptation. The genomic islands νSaα and νSaβ are found in almost all S. aureus strains and are characterized by extensive variation in virulence gene content. However the basis for the diversity and the mechanism underlying mobilization of the genomic islands between strains are unexplained. Here, we demonstrated that the genomic island, νSaβ, encoding an array of virulence factors including staphylococcal superantigens, proteases, and leukotoxins, in addition to bacteriocins, was transferrable in vitro to human and animal strains of multiple S. aureus clones via a resident prophage. The transfer of the νSaβ appears to have been accomplished by multiple conversions of transducing phage particles carrying overlapping segments of the νSaβ. Our findings solve a long-standing mystery regarding the diversification and spread of the genomic island νSaβ, highlighting the central role of bacteriophages in the pathogenic evolution of S. aureus.

No MeSH data available.


Related in: MedlinePlus