The integrated state of the rolling-circle plasmid pTB913 in the composite Bacillus plasmid pTB19

✍ Scribed by Oskam, Linda ;Hillenga, DirkJ. ;Venema, Gerard ;Bron, Sierd

• Book ID: 104691948
• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 719 KB
• Volume: 233
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00265444

✦ Synopsis

pTB19, a 27 kb plasmid originating from a thermophilic Bacillus species, contains integrated copies of two rolling-circle type plasmids on a 10.6 kb DNA fragment. In the present study we analysed the part of pTB19 that contains the rolling-circle plasmid pTB913 and the region in between the two rolling-circle plasmids. We show that, in the integrated state, pTB913 was flanked by a 55 bp direct repeat that duplicated part of the replication initiation gene repB. Since repB was interrupted, the integrated pTB913 could not initiate rolling-circle replication. Autonomously replicating pTB913 was produced from pTB19, probably through recombination between the 55 bp direct repeats; this was a rare event. Since the second integrated rolling-circle type plasmid also contained a non-functional replication initiation gene, replication of pTB19 must be controlled by the RepA determinant. Theta-type replication, controlled by RepA is likely to account for the high stability of pTB19. In between the two integrated rolling-circle plasmids was present an open reading frame (447 codons) which could encode a protein of unknown function.