STRUCTURAL ORGANIZATION OF A CRYPTIC PLASMID, PMA1, FROM MICROCYSTIS-AERUGINOSA F AERUGINOSA KUTZING

The 2287-bp cryptic plasmid, pMA1, from Microcystis aeruginosa f. aeruginosa Kutzing, a unicellular cyanobacterium originally derived from Kasumigaura lake, was completely sequenced and analyzed. The predicted amino acid sequence (253 residues) of an open reading frame had identities of 47%, 48%, and 53% with replication-associated proteins of Bacillus amyloliquefacien's plasmid, pFTB14, B. subtilis BAA1's pBAA1, and B. coagulans's pBC1, respectively, when conservative amino acid substitutions were included. Such high-level identities were also shown with rep proteins and ori regions in a group of Gram-positive bacterial plasmids such as Lactococci and Staphylococci that are known to replicate via single-stranded intermediates. The pMA1 does hybridize with a plasmid, pUS1-3, derived from another unnicellular cyanobacterium, Synechoystis sp. PCC 6803. Novel features of pMA1 are discussed.