Observations on the formation of deletions on monomeric and dimeric plasmids in Escherichia coli
Research output: Contribution to journal › Journal article › Research › peer-review
Standard
Observations on the formation of deletions on monomeric and dimeric plasmids in Escherichia coli. / Ravn, P; Givskov, M; Eegholm, K M; Madsen, S M; Boe, Lars.
In: Molecular Microbiology, Vol. 14, No. 2, 1994, p. 263-70.Research output: Contribution to journal › Journal article › Research › peer-review
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - Observations on the formation of deletions on monomeric and dimeric plasmids in Escherichia coli
AU - Ravn, P
AU - Givskov, M
AU - Eegholm, K M
AU - Madsen, S M
AU - Boe, Lars
PY - 1994
Y1 - 1994
N2 - We have studied the formation of spontaneous mutations on plasmids present in the monomeric and dimeric states in a recF strain of Escherichia coli. Two test systems were employed: (i) the precise excision of Tn5 from the tetA gene of the plasmid pBR322 and (ii) operator constitutive (Oc) mutations on the pBR322-derived plasmid pPY97. The rate of Oc mutations was increased by a factor of three when this plasmid was present in the dimeric state compared to the monomeric state and the Oc phenotype was caused by small deletions in the operator sequence. No apparent mutational hot-spot was found. The rate of Tn5 excision was increased on dimeric compared to monomeric plasmids. Excision from a dimeric plasmid usually resulted in two types of mutant plasmids; a dimeric plasmid, where the Tn5 had excised from one of the plasmid units, and a monomeric parental pBR322. A mechanisms to account for this is suggested. Complementation tests revealed that the increased mutation rate on dimeric plasmids is the result of dimers being mutaphilic per se, rather than the result of a general, trans-acting increase in mutation rates of the host, induced by the presence of the dimeric plasmid. Furthermore, it was found that the rate of Tn5 excision from plasmids in the monomeric state was increased when the region carrying the inserted Tn5 was duplicated.
AB - We have studied the formation of spontaneous mutations on plasmids present in the monomeric and dimeric states in a recF strain of Escherichia coli. Two test systems were employed: (i) the precise excision of Tn5 from the tetA gene of the plasmid pBR322 and (ii) operator constitutive (Oc) mutations on the pBR322-derived plasmid pPY97. The rate of Oc mutations was increased by a factor of three when this plasmid was present in the dimeric state compared to the monomeric state and the Oc phenotype was caused by small deletions in the operator sequence. No apparent mutational hot-spot was found. The rate of Tn5 excision was increased on dimeric compared to monomeric plasmids. Excision from a dimeric plasmid usually resulted in two types of mutant plasmids; a dimeric plasmid, where the Tn5 had excised from one of the plasmid units, and a monomeric parental pBR322. A mechanisms to account for this is suggested. Complementation tests revealed that the increased mutation rate on dimeric plasmids is the result of dimers being mutaphilic per se, rather than the result of a general, trans-acting increase in mutation rates of the host, induced by the presence of the dimeric plasmid. Furthermore, it was found that the rate of Tn5 excision from plasmids in the monomeric state was increased when the region carrying the inserted Tn5 was duplicated.
M3 - Journal article
C2 - 7830571
VL - 14
SP - 263
EP - 270
JO - Molecular Microbiology
JF - Molecular Microbiology
SN - 0950-382X
IS - 2
ER -
ID: 44294070