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  • 11
    Electronic Resource
    Electronic Resource
    Two mutant alleles of mukB, a gene essential for chromosome partition in Escherichia coli (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 123 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The MukB protein is essential for chromosome partitioning in Escherichia coli and consists of 1484 amino acid residues (170 kDa). We have determined the base changes at the mutated sites of the mukB106 mutant and a newly isolated mutant, mukB33. These mutant mukB genes were each found to carry a single base-pair transition which leads to an amino acid substitution; a serine residue at position 33 was changed to phenylalanine in the case of mukB106, and an aspartic acid residue at position 1201 was changed to asparagine in the case of mukB33.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb07196.x
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  • 12
    Electronic Resource
    Electronic Resource
    Characterization of translucent segments observed in an smbA mutant of Escherichia coli (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 116 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The smbA gene of Escherichia coli is essential for cell proliferation. The smbA2 mutant shows cold-sensitive colony formation at 22°C. A novel morphological phenotype, formation of a translucent segment at midcell or at a cell pole, was observed by phase-contrastt microscopy at a high frequency in the smbA2 mutant cells incubated in L medium lacking NaCl at 22°C, but not observed in L medium containing 1% NaCl or 20% sucrose at the same temperature. No translucent segment was observed in the wild-type cells in any of the media used. Electron microscopic observation revealed that the translucent segments resulted from the enlargement of a periplasmic space by separation of the inner membrane from the peptidoglycan layer and the outer membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb06676.x
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  • 13
    Electronic Resource
    Electronic Resource
    Identification of two new genes, mukE  and mukF,  involved in chromosome partitioning in Escherichia coli (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 241-251 
    Details
    ISSN: 1617-4623
    Keywords: Key words mukF ∂ mukE ∂ Chromosome partitioning ∂ Leucine zipper ∂ Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have previously reported that the MukB protein is essential for chromosome partitioning in Escherichia coli and that mukB mutants produce anucleate cells and are temperature-sensitive for colony formation. The mukB gene maps at 21 min on the E. coli chromosome and smtA-mukF-mukE-mukB genes might comprise an operon, which is transcribed in a clockwise direction. Here, we report that mukF and mukE null mutants are both temperature-sensitive for colony formation and produce anucleate cells even at the permissive temperature. These phenotypes are the same as those observed in the mukB null mutant. The primary sequence of MukF includes a leucine zipper structure and an acidic domain. Mutational analysis revealed that both are required for MukF function. When the MukF protein was overproduced in the wild-type strain, anucleate cells were produced. In contrast, overproduction of either MukE or MukB did not cause the defect. In null mutants for the mukF, mukE, and mukB genes, the synchronous initiation of chromosome replication was not affected. The mini-F plasmid was as stably maintained in these mutants as in the wild-type strain. These results indicate that the MukF, MukE, and MukB proteins are involved in the chromosome partitioning steps, but are not required for mini-F plasmid partitioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02174381
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  • 14
    Electronic Resource
    Electronic Resource
    New killing system controlled by two genes located immediately upstream of the mukB gene in Escherichia coli (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 136-147 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; Plasmid Post-segregational killing system ; kicA ; kicB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequence was determined of the region upstream of the mukB gene of Escherichia coli. Two new genes were found, designated kicA and kicB (killing of cell); the gene order is kicB-kicA-mukB. Promoter activities were detected in the regions immediately upstream of kicB and kicA, but not in front of mukB. Gene disruption experiments revealed that the kicA disruptant was nonviable, but the kicB-disrupted mutant and the mutant lacking both the kicB and kicA genes were able to grow. When kicA disruptant cells bearing a temperature-sensitive replication plasmid carrying the kicA + gene were grown at 30° C and then transferred to 42° C, the mutant cells gradually lost colony-forming ability, even in the presence of a mukB + plasmid. Rates of protein synthesis, but not of RNA or DNA synthesis, fell dramatically during incubation at 42° C. These results suggested that the kicB gene encodes a killing factor and the kicA gene codes for a protein that suppresses the killing function of the kicB gene product. It was also demonstrated that KicA and KicB can function as a post-segregational killing system, when the genes are transferred from the E. coli chromosome onto a plasmid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280310
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  • 15
    Electronic Resource
    Electronic Resource
    Initiation of DNA replication in Escherichia coli (1974)
    Springer
    Molecular genetics and genomics 132 (1974), S. 49-62 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When a culture of E. coli strain carrying a temperature-sensitive DNA initiation mutation, dna-167 or dnaC2, is exposed to a nonpermissive temperature for a certain period of time, and then transferred back to a permissive temperature, DNA synthesis is resumed even in the presence of chloramphenicol. This shows that thermolabile components coded by either of these mutated genes can be reactivated after return to permissive temperatures, and consequently initiation of a new replication cycle can occur in the absence of concomitant protein synthesis in both strains. The reinitiation of replication occurring after lowering the temperature is sensitive to rifampicin in the dna-167 cells, but not in the dnaC2 mutant. The capacity for initiating a new round of replication is very labile in the dna-167 mutant, but not in the dnaC2 mutant, when a culture of the mutant is maintained at a nonpermissive temperature in the presence of rifampicin. Mechanisms of blocking of the initiation process with these mutants are discussed. After a prolonged exposure of an early-exponential phase culture to high temperatures, reinitiation of DNA replication never exceeds a doubling in both strains, when the temperature is lowered in the presence of chloramphenicol. However, after an exposure of a late-exponential phase culture to a nonpermissive temperature, more than one round of replication occurs in both strains even in the presence of chloramphenicol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268230
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  • 16
    Electronic Resource
    Electronic Resource
    Replication of Fpoh + plasmid in mafA mutants of Escherichia coli defective in plasmid maintenance (1977)
    Springer
    Molecular genetics and genomics 152 (1977), S. 211-217 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A class of F′ plasmids, designated Fpoh +, was previously shown to be able to replicate extrachromosomally on Hfr strains by virtue of carrying the specific site or region poh + (permissive on Hfr) of the E. coli chromosome (Hiraga, 1975, 1976a). These plasmids were now found to replicate on E. coli mafA mutants (mafA1 and mafA23) that cannot support vegetative replication of F and some other F-like plasmids. The derivatives of Fpoh + that have lost the poh + site, on the other hand, failed to replicate on mafA mutants. These mutants harboring Fpoh + (but not Poh- derivatives thereof) exhibit abnormal cell division and form elongated cells, presumably due to competition between Fpoh + and the host chromosome for some factor(s) essential for the initiation of DNA replication of the both replicons. It is tentatively concluded that the poh + site is required for F′ plasmids to replicate on mafA mutants as well as on Hfr strains. In view of the fact that the mechanism of inhibition of autonomous F DNA replication in mafA mutants and in Hfr strains are clearly different, the present data seem to provide strong support to the notion that the poh + region contains the replication origin of the E. coli chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268820
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  • 17
    Electronic Resource
    Electronic Resource
    Prophage λ induction caused by mini-F plasmid genes (1984)
    Springer
    Molecular genetics and genomics 196 (1984), S. 185-193 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When bacterial cells harboring a temperaturesensitive replication plasmid, which carries the particular ccd segment of a mini-F plasmid, are transferred to 42°C, cell division is inhibited after incubation for an appropriate time. The inhibition occurs, when the copy number of the plasmid decreases to become critically low, about one per cell (Ogura and Hiraga 1983 b). In λ phage lysogens carrying this type of plasmid, the prophage is induced in a small portion of the cell population under the same conditions, in addition to the inhibition of cell division in most of cells. The prophage induction, but not the inhibition of normal cell division, depends on normal recA function. Both induction of prophage and inhibition of cell division are suppressed by the simultaneous presence of a replication proficient plasmid carrying the ccdA gene. We discuss molecular mechanisms of the ccd function that couples host cell division to plasmid proliferation and induces the prophage. Additionally, we propose a hypothesis that the ccd mechanism of F plasmid contributes to indirect induction of prophage λ by an F plasmid damaged by UV-irradiation and then introduced into a lysogen via conjugation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328049
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  • 18
    Electronic Resource
    Electronic Resource
    Involvement of DnaK protein in mini-F plasmid replication: Temperature-sensitive seg mutations are located in the dnaK gene (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 183-189 
    Details
    ISSN: 1617-4623
    Keywords: dnaK gene ; seg mutations ; F plasmid ; Replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seg mutants (seg-1 and seg-2) of Escherichia coli cannot support the replication of the F factor and mini-F plasmids at 42°C. We cloned the wild-type E. coli chromosomal DNA fragment complementing the seg-1 and seg-2 mutations and found that both mutations were complemented by the wild-type dnaK gene coding for a heat shock protein. Transduction with phage P1 indicated that the seg-2 mutation is located at about 0.3 min in the region containing the dnaK gene in the order trpR-thrA-seg-2-leuB, consistent with the locus of the dnaK gene. Cloning and sequencing of the dnaK gene of the seg mutants showed that there was one base substitution within the dnaK gene in each mutant causing an amino acid substitution. These results indicate that the seg gene in which the seg-1 and seg-2 mutations occurred is identical to the dnaK gene. The mini-F plasmid pXX325 did not transform a dnaK null mutant to ampicillin resistance at 30°C in contrast to plasmids pBR322, pACYC184 and pSC101, which did. The active dnaK (seg) gene product is therefore essential for replication of the mini-F plasmid at both 30° and 42°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331267
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  • 19
    Electronic Resource
    Electronic Resource
    A novel type of E. coli mutants with increased chromosomal copy number (1983)
    Springer
    Molecular genetics and genomics 192 (1983), S. 51-60 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have isolated E. coli mutants which can grow at 30°C but not at 42°C and are able to harbor the oriC plasmid (minichromosome) at a higher copy number than the parental wild-type strain at the permissive temperature. The mutants were found to contain higher amounts of chromosomal DNA per mg protein than the wild-type, whether or not they harbor the plasmid. Experimental results suggest that the higher amount of chromosomal DNA is due to a higher copy number of chromosomes and not to a larger amount of DNA per chromosome. These properties in each of the mutants are caused by a single mutation at the rpoB or rpoC gene that code for the β or β′ subunit of RNA polymerase, respectively. The mutations are thought to affect the regulation of replication of oriC-bearing replicons, that is, the E. coli chromosome and oriC plasmids, but not the miniF plasmid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327646
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  • 20
    Electronic Resource
    Electronic Resource
    Purification and characterization of the sopB gene product which is responsible for stable maintenance of mini-F plasmid (1989)
    Springer
    Molecular genetics and genomics 218 (1989), S. 431-436 
    Details
    ISSN: 1617-4623
    Keywords: F plasmid ; Plasmid stability ; DNA binding protein ; SopB protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mini-F plasmid has the trans-acting sopA, sopB genes and the cis-acting sopC DNA which are essential for plasmid partitioning. In this paper, we report the purification of the sopB gene product from extracts of cells harboring a pBR322 derivative carrying the sopB gene. The purity of the final preparation was more than 95%, as determined by densitometry. The amino acid sequence of the amino-terminal region of the protein for the 17 residues identified was identical to that predicted from the DNA sequence of the sopB gene. Therefore, it was concluded that the protein was the sopB gene product. Using anti-SopB serum, the SopB protein was detected in the cell lysates of F+, F′, and Hfr strains. The SopB protein bound to the plasmid DNA of a pBR322 derivative carrying the sopC DNA segment, but not to the vector plasmid pBR322.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332406
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