Identification of plasmids in the genus Marinococcus and complete nucleotide sequence of plasmid pPL1 from Marinococcus halophilus

Several plasmids were detected in the Gram-positive halophilic eubacterium Marinococcus halophilus and in the related strain M52. The complete nucleotide sequence (3874 bp) of one of these plasmids, pPL1, was determined. Four major open reading frames were identified. Whereas orf3 and orf4 showed no sequence similarities to known proteins, rep displayed a high sequence similarity to replication proteins of rolling circle plasmids. Upstream of this ORE a sequence resembling the double-strand origin was detected. A region probably constituting the single-strand origin was identified. The ORF mob showed sequence similarity with Mob proteins of rolling circle plasmids. The observed characteristics suggest that pPL1 replicates according to the rolling circle mechanism. (C) 1998 Academic Press.