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  • 1
    Electronic Resource
    Electronic Resource
    The ypdI gene codes for a putative lipoprotein involved in the synthesis of colanic acid in Escherichia coli (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 235 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In Escherichia coli, the synthesis of colanic acid, an extracellular polysaccharide imminent in biofilm development, is a complicated process involving numerous genes and not yet wholly elucidated. Using a plasmid-borne E. coli K-12 gene library, we have identified a clone whose presence conferred mucoid colony phenotype onto E. coli CM2555 strain. Our results indicate that overexpression of a gene previously catalogued as ypdI, which encodes a putative lipoprotein, is responsible for this phenotype. We show that the mucoidy of ypdI -overexpressing bacteria is due to increased production of colanic acid. This phenotype depends on the function of the rcsA gene, but not on that of rcsF. These results suggest that the ypdI gene product might be an additional factor playing a role in colanic acid synthesis, indicating that this process can be even more complicated than supposed to date. However, no obvious phenotype was observed in the ΔypdI::kan mutant cultivated under standard laboratory conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2004.tb09598.x
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of copy number and stability of phage λ derived pTCλ1 plasmid in the light of the dimer/multimer catastrophe hypothesis (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 176 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The dimer catastrophe hypothesis has been proposed previously to explain instability of multicopy plasmids whose partitioning is random, contrary to low copy number plasmids which are stably maintained and actively partitioned. Until now, this hypothesis has been investigated using multicopy ColE1 plasmids. However, for more detailed testing of the dimer/multimer catastrophe hypothesis, one should use a plasmid which can be maintained at either low or high copy number and still possesses the same mechanism of replication regulation. Here we used a modified λ plasmid, pTCλ1. The advantage of this plasmid is that it can be maintained at different copy numbers depending on the concentration of an inducer which stimulates the initiation of plasmid replication. Results obtained with this plasmid in recombination proficient and deficient cells generally support the dimer/multimer catastrophe hypothesis, but also suggest some modification in the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb13702.x
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  • 3
    Electronic Resource
    Electronic Resource
    The presence of two DnaA-binding sequences is required for an efficient interaction of the Escherichia coli DnaA protein with each particular weak DnaA box region (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 174 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Using an electron microscopic method for visualizing interactions of the Escherichia coli DnaA protein with weak DnaA-binding DNA sequences, we found that DnaA binds effectively to two separated weak DnaA box regions located on the same DNA fragment. As expected, no DnaA-DNA interactions were detected when both DnaA box regions were mutagenized to the sequence totally incapable of binding DnaA. However, when only one of these two regions was mutagenized, the lack of interactions between DnaA and DNA was observed not only at the scrambled DnaA box but also at the second weak DnaA box region. These results indicate that for the efficient binding of DnaA to a weak DnaA box region, the presence of at least two such DNA sequences is necessary. Our finding also suggests that binding of DnaA protein to weak DnaA box sequences may be cooperative. In addition, we found that DnaA-mediated transcription termination in vivo requires two DnaA boxes, one of them is a weak one. It seems, therefore, that some mechanisms of regulation of transcription and DNA replication by DnaA, that involve interactions of DnaA with weak DnaA boxes, may be more complicated than initially proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb13545.x
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  • 4
    Electronic Resource
    Electronic Resource
    Replication and amplification of λ plasmids in Escherichia coli during amino acid starvation and limitation (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 153 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: It was demonstrated previously that replication of plasmids derived from bacteriophage λ (so-called λ plasmids) is inhibited in wild-type Escherichia coli cells starved for isoleucine and arginine whereas it proceeds under the same conditions in relA mutants. Since replication of other replicons during the stringent or relaxed response depends on the nature of the deprived amino acid, we investigated replication of λ plasmids in E. coli relA+ and relA− strains starved for different amino acids. We found that replication of λ plasmids is generally inhibited during the stringent, but not relaxed, response. Differences between cells starved for different amino acids, although reproducible, were not dramatic. Amino acid starvation was previously proposed as a method for amplification of λ plasmid DNA in vivo. We found that during amino acid limitation λ plasmids replicate more extensively in the relA mutants than during amino acid starvation. The efficiency of plasmid DNA amplification was found to be dependent on the kind of limited amino acid; in relA− bacteria limited for leucine we observed about 10-fold plasmid amplification. Some λ plasmid replication was also found under these conditions in the relA+ host. The mechanism of the stringent control of λ plasmid DNA replication has already been proposed. Here the possible mechanism of the regulation of λ plasmid replication during amino acid limitation is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb10476.x
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of some antibiotic-resistance-conferring plasmids on the removal of the heat-aggregated proteins from Escherichia coli cells (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 176 (1999), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We found that the presence of plasmids expressing tetracycline resistance or chloramphenicol resistance genes, but not those expressing ampicillin resistance or kanamycin resistance genes, in Escherichia coli led to the retardation of the process of removal of the heat-aggregated proteins (i.e. the S fraction) from the bacterial cells. The presence of chloramphenicol acetyltransferase in the S fraction is demonstrated. Moreover, we observed that the expression of T7 RNA polymerase gene had an influence on S fraction removal. These results suggest that high level production of some heterologous proteins which are accumulated in the cytoplasm, but not proteins exported through the cell membranes, may cause overloading of the S fraction and delay in the removal of heat-aggregated proteins from bacterial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1999.tb13673.x
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  • 6
    Electronic Resource
    Electronic Resource
    Escherichia coli dnaA gene function and bacteriophage λ replication (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 167 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Allele specificity of the Escherichia coli dnaA gene function in the replication of plasmids derived from bacteriophage λ has been demonstrated previously. Here, using a series of dnaA temperature-sensitive mutants, we investigated dnaA allele specificity of the replication of phages λP+ and λPts1πA66. We found that phage λP+ produces its progeny efficiently at 43°C irrespective of the dnaA allele, whereas λPts1πA66, which is unable to develop lytically in the dnaA+ host at this temperature, can replicate with different efficiency in certain dnaA mutants. Since the main role of DnaA in λ development seems to be stimulation of transcription from the pR promoter, we measured the activity of this promoter (using a pR-lacZ fusion) and the abundance of pR-derived transcripts (by Northern blotting analysis) in dnaA+ host and dnaA(ts) mutants at 30 and 43°C. We found significant differences in the activity of pR in various dnaA(ts) mutants at 30°C, which indicate different levels of stimulation of this promoter by products of particular dnaA alleles at permissive temperature. Differential levels of DnaA-mediated stimulation of pR in various dnaA(ts) mutants were also found at 43°C. Stimulation of the pR promoter by DnaA is necessary for both efficient production of the λ replication proteins, O and P, and effective transcriptional activation of oriλ. The differences in the efficiency of pR activation observed in dnaA mutants at 30 and 43°C can explain the mechanisms of allele specificity of dnaA gene function in the replication of bacteriophage λ and plasmids derived from this phage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb13203.x
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  • 7
    Electronic Resource
    Electronic Resource
    Bioluminescence-mediated stimulation of photoreactivation in bacteria (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 250 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Although biochemistry and genetics of light emission by cells have been investigated in detail, a biological role for bacterial luminescence has remained obscure for a long time. It was proposed recently that luminescence may stimulate DNA repair, but the specific mechanism of this phenomenon was not investigated. Moreover, experiments showing decreased survival of UV-irradiated lux mutants relative to luminescent cells were performed previously using only one bacterial species, Vibrio harveyi. Here, we demonstrate that dark mutants of various strains of naturally luminescent bacteria (Photobacterium leiognathi, Photobacterium phosphoreum and Vibrio fischeri) are more sensitive to UV irradiation than wild-type cells. Thus, this phenomenon occurs not only in V. harveyi but also in other bacterial species. Using an artificial system of luminescent Escherichia coli in combination with phr mutants (defective in photolyase functions), we found that bacterial luminescence may stimulate photoreactivation, perhaps by providing photons that are necessary for photolyase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.06.047
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  • 8
    Electronic Resource
    Electronic Resource
    SeqA, the Escherichia coli origin sequestration protein, is also a specific transcription factor (2001)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 40 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The SeqA protein is a negative regulator of initiation of DNA replication in the Escherichia coli chromosome. Here, we demonstrate that SeqA stimulates transcription from the bacteriophage λpR promoter both in vivo and in vitro. The activity of the λpL promoter was found not to be affected by this protein. SeqA-mediated stimulation of pR was dependent on the state of template methylation: transcription was activated on fully methylated and hemimethylated templates but not on an unmethylated template. Using electrophoretic mobility shift assay and electron microscopy, we demonstrated that SeqA interacts specifically with a pR promoter region located on both fully methylated and hemimethylated DNA molecules, but not on unmethylated DNA. The activity of SeqA was found to affect the initiation of λ plasmid replication positively in vivo, probably via pR-dependent expression of λ replication genes and transcriptional activation of ori λ. We conclude that, apart from its function in the control of DNA replication, SeqA is also a specific transcription factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02480.x
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  • 9
    Electronic Resource
    Electronic Resource
    Neither absence nor excess of λ O initiator-digesting ClpXP protease affects λ plasmid or phage replication in Escherichia coli (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Owing to rapid proteolysis of the coliphage λ-coded initiator protein, λ O, this protein is considered to carry a rate–limiting step in λ DNA replication. The discovery of ClpXP protease responsible for λ O protein turnover allowed an opportunity to verify this hypothesis. However, neither absence nor excess of this protease significantly affected the transformation efficiency and copy number of λ plasmid, or the Kinetics of the λ phage growth. These results are also incompatible with the hypothesis that the stabilization of λ O plays a role in the switch from early (circle-to-circle) to late (rolling-circle) λ phage DNA replication. Tran-scriptional activation of oriλ probably assisted by the Escherichia coli DnaA function, remains as the possible rate-limiting step in λ DNA replication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00441.x
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  • 10
    Electronic Resource
    Electronic Resource
    Allele specificity of the Escherichia coli dnaA gene function in the replication of plasmids derived from phage λ (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 580-586 
    Details
    ISSN: 1617-4623
    Keywords: Key words Regulation of DNA replication ; Coliphage λ ; DnaA initiator ; Transcriptional activation ; Chaperone proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We demonstrate a variation in the effects of seven alleles of the Escherichia coli dnaA gene, which cause temperature sensitivity of initiation of chromosomal replication, on the replication of λ phage-derived plasmids at 30° C. These mutants showed no allele specificity of dnaA function in replication of either of two λπ plasmids studied. On the other hand, the inability of the λP + plasmid to replicate in dnaA508, 46 and 204 cells, in dnaB (groPA15) or in cells that are temperature sensitive for the chaperone genes dnaK756, dnaJ259 and grpE280 at 30° C was suppressible by a single π mutatation. This suggests that it is a common property of the π protein, probably its weaker interaction with DnaB helicase, that is responsible for the suppression. One can also conclude that the DnaA-regulated transcriptional activation of oriλ acts at the step, in which all these gene products cooperate, i.e. during preprimosome loading and chaperone-mediated release of DnaB from P protein inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172404
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