Transposase-Mediated Excision, Conjugative Transfer, and Diversity of ICE6013 Elements in Staphylococcus aureus

• Published in: Journal of bacteriology Vol. 199; no. 8; p. E00629
• Main Authors: Sansevere, Emily A, Luo, Xiao, Park, Joo Youn, Yoon, Sunghyun, Seo, Keun Seok, Robinson, D Ashley
• Format: Journal Article
• Language: English
• Published: Washington American Society for Microbiology 01-04-2017
• Subjects: Bacteriology; Chromosomes; Genetics; Gram-positive bacteria; Plasmids; Spotlight; Staphylococcus aureus; Temperature
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/JB.00629-16

ICE6013 represents one of two families of integrative conjugative elements (ICEs) identified in the pan-genome of the human and animal pathogen Staphylococcus aureus. Here we investigated the excision and conjugation functions of ICE6013 and further characterized the diversity of this element. ICE6013 excision was not significantly affected by growth, temperature, pH, or UV exposure and did not depend on recA. The IS30-like DDE transposase (Tpase; encoded by orf1 and orf2) of ICE6013 must be uninterrupted for excision to occur, whereas disrupting three of the other open reading frames (ORFs) on the element significantly affects the level of excision. We demonstrate that ICE6013 conjugatively transfers to different S. aureus backgrounds at frequencies approaching that of the conjugative plasmid pGO1. We found that excision is required for conjugation, that not all S. aureus backgrounds are successful recipients, and that transconjugants acquire the ability to transfer ICE6013. Sequencing of chromosomal integration sites in serially passaged transconjugants revealed a significant integration site preference for a 15-bp AT-rich palindromic consensus sequence, which surrounds the 3-bp target site that is duplicated upon integration. A sequence analysis of ICE6013 from different host strains of S. aureus and from eight other species of staphylococci identified seven divergent subfamilies of ICE6013 that include sequences previously classified as a transposon, a plasmid, and various ICEs. In summary, these results indicate that the IS30-like Tpase functions as the ICE6013 recombinase and that ICE6013 represents a diverse family of mobile genetic elements that mediate conjugation in staphylococci.