The integrated state of the rolling-circle plasmid pTB913 in the composite Bacillus plasmid pTB19.
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.
Oskam
L
L
Department of Genetics, Biological Centre, University of Groningen, Haren, The Netherlands.
Hillenga
D J
DJ
Venema
G
G
Bron
S
S
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004261:DNA Replication / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics*; D015183:Restriction Mapping; D014170:Transformation, Genetic / Q000235:genetics
D004251:DNA Transposable Elements