Complete nucleotide sequence of pGO1, the prototype conjugative plasmid from the staphylococci

In view of its historical significance as the prototype class III plasmid from the staphylococci, and its ongoing importance as a laboratory tool, we have determined the complete nucleotide sequence of pGO1. At exactly 54 kb, pGO1 is 2–4 kb larger than previously reported, and shares extensive (∼31–46 kb) regions of near identical DNA sequence with other class III plasmids. In particular, we confirm that pGO1 is almost identical to plasmid pSK41 along the entire length of the latter, but additionally contains a co-integrated copy of plasmid pSK639, which accounts for the difference in size (∼8 kb), and the fact that pGO1, but not pSK41, confers resistance to trimethoprim. The pSK639 co-integrant appeared to have undergone mutational inactivation of its mobilization functions, a finding which was confirmed experimentally. Although originally identified through an association with aminoglycoside resistance, the pGO1/pSK41 backbone replicon continues to play a key role in the dissemination of antibiotic resistance determinants in the staphylococci.