pS86, A New Theta-Replicating Plasmid from Enterococcus faecalis

The complete nucleotide sequence of the small (5149 bp) and cryptic plasmid pS86 from Enterococcus faecalis ssp. faecalis S-86 has been determined. Sequence analysis revealed six putative open reading frames (ORFs) encoding polypeptides of 28.3, 11.5, 8.4, 65.1, 7.3, and 11.96 kDa each. Based on sequence similarity, two cassettes have been identified in pS86: ORF1 codes for the replication initiation protein (Rep); ORF4 codes for a putative mobilization protein that shows similarities to Mob/Pre proteins from plasmids of Gram-positive bacteria. No function could be assigned to the other putative ORFs found. According to our results, pS86 plasmid could use a theta-mode of replication, similar to the recently described theta-type replicons from pUCL287 (Tetragenococcus halophila) and pLA1 or pLA105 (Lactobacillus acidophilus) plasmids.