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  1. Article ; Online: Requirements for Borrelia burgdorferi plasmid maintenance.

    Tilly, Kit / Checroun, Claire / Rosa, Patricia A

    Plasmid

    2012  Volume 68, Issue 1, Page(s) 1–12

    Abstract: Borrelia burgdorferi has multiple linear and circular plasmids that are faithfully replicated and partitioned as the bacterium grows and divides. The low copy number of these replicons implies that active partitioning contributes to plasmid stability. ... ...

    Abstract Borrelia burgdorferi has multiple linear and circular plasmids that are faithfully replicated and partitioned as the bacterium grows and divides. The low copy number of these replicons implies that active partitioning contributes to plasmid stability. Analyzing the requirements for plasmid replication and partition in B. burgdorferi is complicated by the complexity of the genome and the possibility that products may act in trans. Consequently, we have studied the replication-partition region (bbb10-13) of the B. burgdorferi 26kb circular plasmid (cp26) in Escherichia coli, by fusion with a partition-defective miniF plasmid. Our analysis demonstrated that bbb10, bbb11, and bbb13 are required for stable miniF maintenance, whereas bbb12 is dispensable. To validate these results, we attempted to inactivate two of these genes in B. burgdorferi. bbb12 mutants were obtained at a typical frequency, suggesting that the bbb12 product is dispensable for cp26 maintenance as well. We could not directly measure cp26 stability in the bbb12 mutant, because cp26 carries essential genes, and bacteria that have lost cp26 are inviable. Conversely, we were unable to inactivate bbb10 on cp26 of B. burgdorferi. Our results suggest that bbb12 is dispensable for cp26 maintenance, whereas bbb10, bbb11, and bbb13 play crucial roles in that process.
    MeSH term(s) Base Sequence ; Borrelia burgdorferi/genetics ; Cloning, Molecular ; DNA Replication ; Escherichia coli/genetics ; Gene Dosage ; Genes, Essential ; Genetic Complementation Test ; Molecular Sequence Data ; Mutation ; Plasmids
    Language English
    Publishing date 2012-01-24
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Intramural
    ZDB-ID 282384-6
    ISSN 1095-9890 ; 0147-619X
    ISSN (online) 1095-9890
    ISSN 0147-619X
    DOI 10.1016/j.plasmid.2012.01.009
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Requirements for Borrelia burgdorferi plasmid maintenance

    Tilly, Kit / Checroun, Claire / Rosa, Patricia A

    Plasmid. 2012 July, v. 68, no. 1

    2012  

    Abstract: Borrelia burgdorferi has multiple linear and circular plasmids that are faithfully replicated and partitioned as the bacterium grows and divides. The low copy number of these replicons implies that active partitioning contributes to plasmid stability. ... ...

    Abstract Borrelia burgdorferi has multiple linear and circular plasmids that are faithfully replicated and partitioned as the bacterium grows and divides. The low copy number of these replicons implies that active partitioning contributes to plasmid stability. Analyzing the requirements for plasmid replication and partition in B. burgdorferi is complicated by the complexity of the genome and the possibility that products may act in trans. Consequently, we have studied the replication–partition region (bbb10–13) of the B. burgdorferi 26kb circular plasmid (cp26) in Escherichia coli, by fusion with a partition-defective miniF plasmid. Our analysis demonstrated that bbb10, bbb11, and bbb13 are required for stable miniF maintenance, whereas bbb12 is dispensable. To validate these results, we attempted to inactivate two of these genes in B. burgdorferi. bbb12 mutants were obtained at a typical frequency, suggesting that the bbb12 product is dispensable for cp26 maintenance as well. We could not directly measure cp26 stability in the bbb12 mutant, because cp26 carries essential genes, and bacteria that have lost cp26 are inviable. Conversely, we were unable to inactivate bbb10 on cp26 of B. burgdorferi. Our results suggest that bbb12 is dispensable for cp26 maintenance, whereas bbb10, bbb11, and bbb13 play crucial roles in that process.
    Keywords Borrelia burgdorferi ; Escherichia coli ; bacteria ; essential genes ; mutants ; plasmids
    Language English
    Dates of publication 2012-07
    Size p. 1-12.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 282384-6
    ISSN 1095-9890 ; 0147-619X
    ISSN (online) 1095-9890
    ISSN 0147-619X
    DOI 10.1016/j.plasmid.2012.01.009
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: Sigma(s)-dependent regulation of yehZYXW, which encodes a putative osmoprotectant ABC transporter of Escherichia coli.

    Checroun, Claire / Gutierrez, Claude

    FEMS microbiology letters

    2004  Volume 236, Issue 2, Page(s) 221–226

    Abstract: The Escherichia coli yehZYXW operon encodes a putative osmoprotectant uptake system of the ABC transporter family. yehZ is identical to osmF, an osmotically inducible gene identified previously. Construction and analysis of a yehZ-lacZ transcriptional ... ...

    Abstract The Escherichia coli yehZYXW operon encodes a putative osmoprotectant uptake system of the ABC transporter family. yehZ is identical to osmF, an osmotically inducible gene identified previously. Construction and analysis of a yehZ-lacZ transcriptional fusion demonstrated that yehZ is inducible not only by osmolarity, but also upon entry into stationary phase. The osmotic and growth-phase regulations operate at a unique promoter, yehZp, and are totally dependent on the stress specific sigma factor sigma(s). The yehZYXW encoded ABC transporter appears as an additional element of the global stress response controlled by sigma(s).
    MeSH term(s) ATP-Binding Cassette Transporters/chemistry ; ATP-Binding Cassette Transporters/genetics ; ATP-Binding Cassette Transporters/metabolism ; Adaptation, Physiological ; Amino Acid Sequence ; Artificial Gene Fusion ; Bacterial Proteins/metabolism ; Base Sequence ; Escherichia coli/genetics ; Escherichia coli/metabolism ; Escherichia coli Proteins/genetics ; Escherichia coli Proteins/metabolism ; Gene Expression Regulation, Bacterial ; Gene Order ; Genes, Bacterial ; Genes, Reporter ; Molecular Sequence Data ; Operon ; Osmolar Concentration ; Promoter Regions, Genetic ; Sigma Factor/metabolism ; Transcription Initiation Site ; beta-Galactosidase/genetics ; beta-Galactosidase/metabolism
    Chemical Substances Bacterial Proteins ; Escherichia coli Proteins ; Sigma Factor ; sigma factor KatF protein, Bacteria ; beta-Galactosidase (EC 3.2.1.23)
    Language English
    Publishing date 2004-07-15
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 752343-9
    ISSN 1574-6968 ; 0378-1097
    ISSN (online) 1574-6968
    ISSN 0378-1097
    DOI 10.1016/j.femsle.2004.05.046
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    Zs.A 1372: Show issues Location:
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  4. Article ; Online: Interactions between the 2.4 and 4.2 regions of sigmaS, the stress-specific sigma factor of Escherichia coli, and the -10 and -35 promoter elements.

    Checroun, Claire / Bordes, Patricia / Leroy, Olivier / Kolb, Annie / Gutierrez, Claude

    Nucleic acids research

    2004  Volume 32, Issue 1, Page(s) 45–53

    Abstract: The sigmas subunit of Escherichia coli RNA polymerase holoenzyme (EsigmaS) is a key factor of gene expression upon entry into stationary phase and in stressful conditions. The selectivity of promoter recognition by EsigmaS and the housekeeping Esigma70 ... ...

    Abstract The sigmas subunit of Escherichia coli RNA polymerase holoenzyme (EsigmaS) is a key factor of gene expression upon entry into stationary phase and in stressful conditions. The selectivity of promoter recognition by EsigmaS and the housekeeping Esigma70 is as yet not clearly understood. We used a genetic approach to investigate the interaction of sigmaS with its target promoters. Starting with down-promoter variants of a sigmaS promoter target, osmEp, altered in the -10 or -35 elements, we isolated mutant forms of sigmaS suppressing the promoter defects. The activity of these suppressors on variants of osmEp and ficp, another target of sigmaS, indicated that sigmaS is able to interact with the same key features within a promoter sequence as sigma70. Indeed, (i) sigmaS can recognize the -35 element of some but not all its target promoters, through interactions with its 4.2 region; and (ii) amino acids within the 2.4 region participate in the recognition of the -10 element. More specifically, residues Q152 and E155 contribute to the strong preference of sigmaS for a C in position -13 and residue R299 can interact with the -31 nucleotide in the -35 element of the target promoters.
    MeSH term(s) Amino Acid Sequence ; Amino Acid Substitution/genetics ; Bacterial Proteins/chemistry ; Bacterial Proteins/genetics ; Bacterial Proteins/metabolism ; Base Sequence ; Binding Sites ; Escherichia coli/genetics ; Escherichia coli Proteins/chemistry ; Escherichia coli Proteins/genetics ; Escherichia coli Proteins/metabolism ; Gene Expression Regulation, Bacterial ; Genes, Bacterial/genetics ; Holoenzymes/chemistry ; Holoenzymes/genetics ; Holoenzymes/metabolism ; Membrane Proteins/genetics ; Molecular Sequence Data ; Mutation/genetics ; Promoter Regions, Genetic/genetics ; Protein Binding ; Response Elements/genetics ; Sigma Factor/chemistry ; Sigma Factor/genetics ; Sigma Factor/metabolism ; Suppression, Genetic/genetics
    Chemical Substances Bacterial Proteins ; Escherichia coli Proteins ; Holoenzymes ; Membrane Proteins ; OsmE protein, E coli ; Sigma Factor ; sigma factor KatF protein, Bacteria
    Language English
    Publishing date 2004-01-02
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 186809-3
    ISSN 1362-4962 ; 1362-4954 ; 0301-5610 ; 0305-1048
    ISSN (online) 1362-4962 ; 1362-4954
    ISSN 0301-5610 ; 0305-1048
    DOI 10.1093/nar/gkh155
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    Zs.A 1067: Show issues Location:
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  5. Article: Autophagy-mediated reentry of Francisella tularensis into the endocytic compartment after cytoplasmic replication.

    Checroun, Claire / Wehrly, Tara D / Fischer, Elizabeth R / Hayes, Stanley F / Celli, Jean

    Proceedings of the National Academy of Sciences of the United States of America

    2006  Volume 103, Issue 39, Page(s) 14578–14583

    Abstract: Intracellular bacterial pathogens evade the bactericidal functions of mammalian cells by physical escape from their phagosome and replication into the cytoplasm or through the modulation of phagosome maturation and biogenesis of a membrane-bound ... ...

    Abstract Intracellular bacterial pathogens evade the bactericidal functions of mammalian cells by physical escape from their phagosome and replication into the cytoplasm or through the modulation of phagosome maturation and biogenesis of a membrane-bound replicative organelle. Here, we detail in murine primary macrophages the intracellular life cycle of Francisella tularensis, a highly infectious bacterium that survives and replicates within mammalian cells. After transient interactions with the endocytic pathway, bacteria escaped from their phagosome by 1 h after infection and underwent replication in the cytoplasm from 4 to 20 h after infection. Unexpectedly, the majority of bacteria were subsequently found to be enclosed within large, juxtanuclear, LAMP-1-positive vacuoles called Francisella-containing vacuoles (FCVs). FCV formation required intracytoplasmic replication of bacteria. Using electron and fluorescence microscopy, we observed that the FCVs contained morphologically intact bacteria, despite fusing with lysosomes. FCVs are multimembranous structures that accumulate monodansylcadaverine and display the autophagy-specific protein LC3 on their membrane. Formation of FCVs was significantly inhibited by 3-methyladenine, confirming a role for the autophagic pathway in the biogenesis of these organelles. Taken together, our results demonstrate that, via autophagy, F. tularensis reenters the endocytic pathway after cytoplasmic replication, a process thus far undescribed for intracellular pathogens.
    MeSH term(s) Animals ; Autophagy/physiology ; Bacterial Vaccines ; Cell Membrane/ultrastructure ; Cells, Cultured ; DNA Replication ; Endocytosis/physiology ; Female ; Flow Cytometry ; Francisella tularensis/physiology ; Lysosomes/microbiology ; Macrophages/cytology ; Macrophages/microbiology ; Macrophages/ultrastructure ; Mice ; Mice, Inbred C57BL ; Phagosomes/ultrastructure ; Vacuoles/microbiology ; Vacuoles/ultrastructure
    Chemical Substances Bacterial Vaccines
    Language English
    Publishing date 2006-09-26
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Intramural
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.0601838103
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    Zs.A 1148: Show issues Location:
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  6. Article ; Online: A glutamine-amidotransferase-like protein modulates FixT anti-kinase activity in Sinorhizobium meliloti

    Boistard Pierre / Garnerone Anne-Marie / Guiral Sébastien / Checroun Claire / Bergès Hélène / Batut Jacques

    BMC Microbiology, Vol 1, Iss 1, p

    2001  Volume 6

    Abstract: Abstract Background Nitrogen fixation gene expression in Sinorhizobium meliloti , the alfalfa symbiont, depends on a cascade of regulation that involves both positive and negative control. On top of the cascade, the two-component regulatory system FixLJ ... ...

    Abstract Abstract Background Nitrogen fixation gene expression in Sinorhizobium meliloti , the alfalfa symbiont, depends on a cascade of regulation that involves both positive and negative control. On top of the cascade, the two-component regulatory system FixLJ is activated under the microoxic conditions of the nodule. In addition, activity of the FixLJ system is inhibited by a specific anti-kinase protein, FixT. The physiological significance of this negative regulation by FixT was so far unknown. Results We have isolated by random Tn5 mutagenesis a S. meliloti mutant strain that escapes repression by FixT. Complementation test and DNA analysis revealed that inactivation of an asparagine synthetase-like gene was responsible for the phenotype of the mutant. This gene, that was named asnO , encodes a protein homologous to glutamine-dependent asparagine synthetases. The asnO gene did not appear to affect asparagine biosynthesis and may instead serve a regulatory function in S. meliloti . We provide evidence that asnO is active during symbiosis . Conclusions Isolation of the asnO mutant argues for the existence of a physiological regulation associated with fixT and makes it unlikely that fixT serves a mere homeostatic function in S. meliloti . Our data suggest that asnO might control activity of the FixT protein, in a way that remains to be elucidated. A proposed role for asnO might be to couple nitrogen fixation gene expression in S. meliloti to the nitrogen needs of the cells.
    Keywords Microbiology ; QR1-502 ; Science ; Q ; DOAJ:Microbiology ; DOAJ:Biology ; DOAJ:Biology and Life Sciences
    Subject code 570
    Language English
    Publishing date 2001-05-01T00:00:00Z
    Publisher BioMed Central
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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