As the name implies, 89K is approximately 89 kb in length, flanked by a perfect 15 bp direct repeat, and contains a putative phage-related integrase gene at its 3′ end. These architectural features strongly suggest that it may have been acquired by horizontal gene transfer (HGT). Meanwhile, the internal modular organization of 89K indicates that it was generated by multiple recombination events because it carries several unrelated gene blocks found in widely divergent species, making it difficult to ascertain its initial origin. A better understanding of the molecular biology of 89K will undoubtedly provide important insight into the emergence, virulence, and evolution of this important pathogen. Indeed, it may reveal some clues concerning the molecular pathogenesis of STSS caused by S. suis 2.