Identification and nucleotide sequence analysis of a cryptic plasmid, pRM21, from Rhodothermus marinus

Here we report the identification and nucleotide sequence analysis of pRM21, a plasmid isolated from the thermophilic eubacterium Rhodothermus marinus. pRM21 consists of 2935 bp, has a G+C content of 58.2% and one major open reading frame whose deduced product shows significant similarities to RepA proteins from several plasmids, the highest being to the RepA of pSa from Escherichia coli. A region with the characteristics of iteron-containing replicons, three 19 bp repeats, DnaA boxes, an A+T rich region and GATC sequences, was identified. Of 40 additional R. marinus strains screened for plasmids, six (15%) were found to harbour plasmids with the same size and restriction pattern as pRM21.