scholarly journals Nutritional conditions and oxygen concentration affect spontaneous occurrence of homologous recombination events but not spontaneous mutagenesis in Escherichia coli

2020 ◽  
Vol 95 (2) ◽  
pp. 85-93 ◽  
Author(s):  
Lan Anh Thi Le ◽  
Phooi Yee Chang ◽  
Sayaka Ando ◽  
Thomas M. Conrad ◽  
Shohei Nunose ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Oxygen Concentration ◽  
Spontaneous Mutagenesis ◽  
Nutritional Conditions ◽  
Spontaneous Occurrence

scholarly journals Perfringolysin O Expression in Clostridium perfringens Is Independent of the Upstream pfoR Gene

2002 ◽  
Vol 184 (7) ◽  
pp. 2034-2038 ◽  
Author(s):  
Milena M. Awad ◽  
Julian I. Rood
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Gene Product ◽  
Structural Gene ◽  
Clostridium Perfringens ◽  
Deletion Mutant ◽  
Gas Gangrene ◽  
Alpha Toxin ◽  
Clostridial Myonecrosis ◽  
Perfringolysin O

ABSTRACT The pathogenesis of Clostridium perfringens-mediated gas gangrene or clostridial myonecrosis involves the extracellular toxins alpha-toxin and perfringolysin O. Previous studies (T. Shimizu, A. Okabe, J. Minami, and H. Hayashi, Infect. Immun. 59:137-142, 1991) carried out with Escherichia coli suggested that the perfringolysin O structural gene, pfoA, was positively regulated by the product of the upstream pfoR gene. In an attempt to confirm this hypothesis in C. perfringens, a pfoR-pfoA deletion mutant was complemented with isogenic pfoA+ shuttle plasmids that varied only in their ability to encode an intact pfoR gene. No difference in the ability to produce perfringolysin O was observed for C. perfringens strains carrying these plasmids. In addition, chromosomal pfoR mutants were constructed by homologous recombination in C. perfringens. Again no difference in perfringolysin O activity was observed. Since it was not possible to alter perfringolysin O expression by mutation of pfoR, it was concluded that the pfoR gene product is unlikely to have a role in the regulation of pfoA expression in C. perfringens.

Rapid and apparently error-prone excision repair of nonreplicating UV-irradiated plasmids in Xenopus laevis oocytes

1990 ◽  
Vol 10 (7) ◽  
pp. 3505-3511
Author(s):  
J B Hays ◽  
E J Ackerman ◽  
Q S Pang
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Plasmid Dna ◽  
Excision Repair ◽  
Xenopus Laevis Oocytes ◽  
Marked Contrast ◽  
Repair Synthesis ◽  
Error Frequency ◽  
Repair Activity ◽  
Good Agreement

Repair of UV-irradiated plasmid DNA microinjected into frog oocytes was measured by two techniques: transformation of repair-deficient (delta uvrB delta recA delta phr) bacteria, and removal of UV endonuclease-sensitive sites (ESS). Transformation efficiencies relative to unirradiated plasmids were used to estimate the number of lethal lesions; the latter were assumed to be Poisson distributed. These estimates were in good agreement with measurements of ESS. By both criteria, plasmid DNA was efficiently repaired, mostly during the first 2 h, when as many as 2 x 10(10) lethal lesions were removed per oocyte. This rate is about 10(6) times the average for removal of ESS from repair-proficient human cells. Repair was slower but still significant after 2 h, but some lethal lesions usually remained after overnight incubation. Most repair occurred in the absence of light, in marked contrast to differentiated frog cells, previously shown to possess photoreactivating but no excision repair activity. There was no increase in the resistance to DpnI restriction of plasmids (methylated in Escherichia coli at GATC sites) incubated in oocytes; this implies no increase in hemimethylated GATC sites, and hence no semiconservative DNA replication. Plasmid substrates capable of either intramolecular or intermolecular homologous recombination were not recombined, whether UV-irradiated or not. Repair of Lac+ plasmids was accompanied by a significant UV-dependent increase in the frequency of Lac- mutants, corresponding to a repair synthesis error frequency on the order of 10(-4) per nucleotide.

scholarly journals Chi-Dependent Intramolecular Recombination in Escherichia coli

Genetics ◽  
1998 ◽  
Vol 148 (2) ◽  
pp. 545-557
Author(s):  
Rachel Friedman-Ohana ◽  
Iris Karunker ◽  
Amikam Cohen
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Experimental System ◽  
Cis Acting ◽  
Enzymes Activity ◽  
Intramolecular Recombination ◽  
Insight Into

Abstract Homologous recombination in Escherichia coli is enhanced by a cis-acting octamer sequence named Chi (5′-GCTGGTGG-3′) that interacts with RecBCD. To gain insight into the mechanism of Chi-enhanced recombination, we recruited an experimental system that permits physical monitoring of intramolecular recombination by linear substrates released by in vivo restriction from infecting chimera phage. Recombination of the released substrates depended on recA, recBCD and cis-acting Chi octamers. Recombination proficiency was lowered by a xonA mutation and by mutations that inactivated the RuvABC and RecG resolution enzymes. Activity of Chi sites was influenced by their locations and by the number of Chi octamers at each site. A single Chi site stimulated recombination, but a combination of Chi sites on the two homologs was synergistic. These data suggest a role for Chi at both ends of the linear substrate. Chi was lost in all recombinational exchanges stimulated by a single Chi site. Exchanges in substrates with Chi sites on both homologs occurred in the interval between the sites as well as in the flanking interval. These observations suggest that the generation of circular products by intramolecular recombination involves Chi-dependent processing of one end by RecBCD and pairing of the processed end with its duplex homolog.

An Efficient Site-Directed Mutagenesis Method In Vivo in Escherichia Coli

2012 ◽  
Vol 195-196 ◽  
pp. 407-411
Author(s):  
Mu Qing Qiu
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Recombinant Plasmid ◽  
Genomic Dna ◽  
Gene Replacement ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis

In order to develop an efficient site-directed mutagenesis method in vivo, the tests were tested by the following methods. The methods that the fragment knockouted ompR gene was constructed through overlapping PCR, digested by Notand Sal, ligated to plasmid pKOV were applied. The recombination plasmid was transformed into Escherichia coli WMC-001 strain, integrated into the genomic DNA through two step homologous recombination. The Escherichia coli WMC-001/ompR-mutant was obtained due to gene replacement. The fragment of the mutant ompR gene was amplified through overlapping PCR, cloned into pKOV vector. The recombinant plasmid was introduced into Escherichia coli WMC-001/ompR-mutant. The Escherichia coli WMC-001/ompR mutant was also obtained due to gene replacement. Results: The site-directed mutagenesis has been successfully constructed in the ompR gene by sequencing. Conclusion: The method is effective for construction of gene site-directed mutagenesis in vivo.

scholarly journals Roles of the DNA binding proteins H-NS and StpA in homologous recombination and repair of bleomycin-induced damage in Escherichia coli

2007 ◽  
Vol 82 (5) ◽  
pp. 433-439 ◽  
Author(s):  
Kouya Shiraishi ◽  
Yasuyuki Ogata ◽  
Katsuhiro Hanada ◽  
Yasunobu Kano ◽  
Hideo Ikeda
Keyword(s):  
Escherichia Coli ◽  
Dna Binding ◽  
Homologous Recombination ◽  
Binding Proteins ◽  
Dna Binding Proteins

Prophage λ Induces Terminal Recombination in Escherichia coli by Inhibiting Chromosome Dimer Resolution: An Orientation-Dependent cis-Effect Lending Support to Bipolarization of the Terminus

Genetics ◽  
2000 ◽  
Vol 154 (1) ◽  
pp. 39-48
Author(s):  
Jacqueline Corre ◽  
Josette Patte ◽  
Jean-Michel Louarn
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Primary Effect ◽  
Wild Type ◽  
Skewed Distributions ◽  
Regional Control ◽  
Chromosome Arm ◽  
Sequence Elements

Abstract A prophage λ inserted by homologous recombination near dif, the chromosome dimer resolution site of Escherichia coli, is excised at a frequency that depends on its orientation with respect to dif. In wild-type cells, terminal hyper-(TH) recombination is prophage specific and undetectable by a test involving deletion of chromosomal segments between repeats identical to those used for prophage insertion. TH recombination is, however, detected in both excision and deletion assays when Δdif, xerC, or ftsK mutations inhibit dimer resolution: lack of specialized resolution apparently results in recombinogenic lesions near dif. We also observed that the presence near dif of the prophage, in the orientation causing TH recombination, inhibits dif resolution activity. By its recombinogenic effect, this inhibition explains the enhanced prophage excision in wild-type cells. The primary effect of the prophage is probably an alteration of the dimer resolution regional control, which requires that dif is flanked by suitably oriented (polarized) stretches of DNA. Our model postulates that the prophage inserted near dif in the deleterious orientation disturbs chromosome polarization on the side of the site where it is integrated, because λ DNA, like the chromosome, is polarized by sequence elements. Candidate sequences are oligomers that display skewed distributions on each oriC-dif chromosome arm and on λ DNA.

The initiation and control of homologous recombination in Escherichia coli

1995 ◽  
pp. 9-16
Author(s):  
Gerald R. Smith ◽  
Susan K. Amundsen ◽  
Patrick Dabert ◽  
Andrew F. Taylor
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
And Control
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