ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Evidence for a rolling-circle mechanism of phage DNA synthesis from both replicative and integrated forms of CTXφ (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 41 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes encoding cholera toxin, the principal virulence factor of Vibrio cholerae, are part of the circular single-stranded DNA genome of CTXφ. In toxigenic V. cholerae strains, the CTXφ genome is typically found in integrated arrays of tandemly arranged CTX prophages. Infected cells that lack a chromosomal integration site harbour the CTXφ genome as a plasmid (pCTX). We studied the replication of pCTX and found several indications that this plasmid replicates via a rolling-circle (RC) mechanism. The initiation and termination sites for pCTX plus-strand DNA synthesis were mapped to a 22 bp sequence that contains inverted repeats and a nonanucleotide motif found in the plus-strand origins of several RC replicons. Furthermore, similar to other RC replicons, replication of plasmids containing duplicated pCTX origins resulted in the deletion of sequences between the two origins and the formation of a single chimeric origin. Our previous work revealed that CTX prophage arrays give rise to hybrid CTX virions that contain sequences derived from two adjacent prophages. We now report that the boundaries between the sequences contributed to virions by the upstream and the downstream prophages in an array correspond to the site at which synthesis of plus-strand pCTX DNA is initiated and terminated. These data support the model that plus-strand CTXφ DNA is generated from chromosomal prophages via a novel process analogous to RC replication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02517.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Bacteriophage control of Shiga toxin 1 production and release by Escherichia coli (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The stx genes of many Shiga toxin-encoding Escherichia coli (STEC) strains are encoded by prophages of the λ bacteriophage family. In the genome of the Stx1-encoding phage H-19B, the stx1AB genes are found ≈ 1 kb downstream of the late phage promoter, pR′, but are known to be regulated by the associated iron-regulated promoter, pStx1. Growth of H-19B lysogens in low iron concentrations or in conditions that induce the prophage results in increased Stx1 production. Although the mechanism by which low iron concentration induces Stx1 production is well understood, the mechanisms by which phage induction enhances toxin production have not been extensively characterized. The studies reported here identify the factors that contribute to Stx1 production after induction of the H-19B prophage. We found that replication of the phage genome, with the associated increase in stx1AB copy number, is the most quantitatively important mechanism by which H-19B induction increases Stx1 production. Three promoters are shown to be involved in stx1AB transcription after phage induction, the iron-regulated pStx1 and the phage-regulated pR and pR′ promoters, the relative importance of which varies with environmental conditions. Late phage transcription initiating at the pR′ promoter, contrary to previous findings in the related Stx2-encoding phage φ361, was found to be unnecessary for high-level Stx1 production after phage induction. Finally, we present evidence that phage-mediated lysis regulates the quantity of Stx1 produced by determining the duration of Stx1 accumulation and provides a mechanism for Stx1 release. By amplifying stx1AB copy number, regulating stx1AB transcription and allowing for Stx1 release, the biology of the Stx-encoding phages contributes greatly to the production of Stx, the principal virulence factor of STEC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02950.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Site-specific integration of the conjugal Vibrio cholerae SXT element into prfC (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Vibrio cholerae O139, the first non-O1 serogroup of V. cholerae to give rise to epidemic cholera, is characteristically resistant to the antibiotics sulphamethoxazole, trimethoprim, chloramphenicol and streptomycin. Resistances to these antibiotics are encoded by a 62 kb self-transmissible, conjugative, chromosomally integrating element designated the ‘SXT element’. We found that the SXT element integrates site specifically into both V. cholerae and Escherichia coli K-12 into the 5′ end of prfC, the gene encoding peptide chain release factor 3. Integration of the SXT element interrupts the chromosomal prfC gene, but the element encodes a new 5′ end of prfC that restores the reading frame of this gene. The recombinant prfC allele created upon element integration is functional. The integration and excision mechanism of the SXT element shares many features with site-specific recombination found in lambdoid phages. First, like λ, the SXT element forms a circular extrachromosomal intermediate through specific recombination of the left and right ends of the integrated element. Second, chromosomal integration of the element occurs via site-specific recombination in a 17 bp sequence found in the circular form of the SXT element and a similar 17 bp sequence in prfC. Third, both chromosomal integration and excision of the SXT element were found to require an element-encoded int gene with strong similarities to the λ integrase family. Based on the properties of the SXT element, we propose to classify this element as a CONSTIN, an acronym for a conjugative, self-transmissible, integrating element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01330.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Regulation, replication, and integration functions of the Vibrio cholerae CTXφ are encoded by region RS2 (1997)
    Oxford UK : Blackwell Science Ltd
    Molecular microbiology 24 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: CTXφ is a filamentous phage that encodes cholera toxin, one of the principal virulence factors of Vibrio cholerae. CTXφ is unusual among filamentous phages because it can either replicate as a plasmid or integrate into the V. cholerae chromosome at a specific site. The CTXφ genome has two regions, the ‘core’ and RS2. Integrated CTXφ is frequently flanked by an element known as RS1 which is related to RS2. The nucleotide sequences of RS2 and RS1 were determined. These related elements contain three nearly identical open reading frames (ORFs), which in RS2 were designated rstR, rstA2 and rstB2. RS1 contains an additional ORF designated rstC. Functional analyses indicate that rstA2 is required for CTXφ replication and rstB2 is required for CTXφ integration. The amino terminus of RstR is similar to the amino termini of other phage-encoded repressors, and RstR represses the expression of rstA2. Although genes with related functions are clustered in the genome of CTXφ in a way similar to those for other filamentous phages, the CTXφ RS2-encoded gene products mediating replication, integration and repression appear to be novel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.3911758.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Replication and integration of a Vibrio cholerae cryptic plasmid linked to the CTX prophage (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We identified a 4.7 kb cryptic plasmid in all ctxAB+Vibrio cholerae strains we tested. An isolate of the V. cholerae classical biotype strain O395 that harbours the cryptic plasmid at high copy number was found. Hybridization analysis demonstrated that sequences highly related or identical to this plasmid exist in all toxigenic strains of V. cholerae but were notably absent in all non-toxigenic environmental isolates that lacked the genes for toxin-co-regulated pili and the filamentous CTX prophage. Accordingly, we have named the cryptic plasmid pTLC for toxin-linked cryptic. The complete nucleotide sequence of pTLC from the high-copy-number isolate was determined. The largest open reading frame in the plasmid is predicted to encode a protein similar to the replication initiation protein (pII) of Escherichia coli F-specific filamentous phages. The nucleotide sequence of pTLC also facilitated the structural characterization of the DNA homologous to pTLC in other strains of V. cholerae. pTLC-related DNA exists in these strains as both low-copy-number, covalently closed circular DNA and tandemly duplicated, chromosomally integrated DNA. Remarkably, the chromosomally integrated form of pTLC is adjacent to the CTX prophage. The strain distribution, chromosomal location and DNA sequence of pTLC suggests that it may be a genetic element that plays some role in the biology of CTXφ, perhaps facilitating either its acquisition or its replication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00889.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Distinct segregation dynamics of the two Vibrio cholerae chromosomes (2005)
    Oxford, UK : Blackwell Publishing Ltd.
    Molecular microbiology 55 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The study of prokaryotic chromosome segregation has focused primarily on bacteria with single circular chromosomes. Little is known about segregation in bacteria with multipartite genomes. The human diarrhoeal pathogen Vibrio cholerae has two circular chromosomes of unequal sizes. Using static and time-lapse fluorescence microscopy, we visualized the localization and segregation of the origins of replication of the V. cholerae chromosomes. In all stages of the cell cycle, the two origins localized to distinct subcellular locations. In newborn cells, the origin of chromosome I (oriCIvc) was located near the cell pole while the origin of chromosome II (oriCIIvc) was at the cell centre. Segregation of oriCIvc occurred asymmetrically from a polar position, with one duplicated origin traversing the length of the cell towards the opposite pole and the other remaining relatively fixed. In contrast, oriCIIvc segregated later in the cell cycle than oriCIvc and the two duplicated oriCIIvc regions repositioned to the new cell centres. DAPI staining of the nucleoid demonstrated that both origin regions were localized to the edge of the visible nucleoid and that oriCIvc foci were often associated with specific nucleoid substructures. The differences in localization and timing of segregation of oriCIvc and oriCIIvc suggest that distinct mechanisms govern the segregation of the two V. cholerae chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04379.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    MicroReview: Divided genomes: negotiating the cell cycle in prokaryotes with multiple chromosomes (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 56 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Historically, the prokaryotic genome was assumed to consist of a single circular replicon. However, as more microbial genome sequencing projects are completed, it is becoming clear that multipartite genomes comprised of more than one chromosome are not unusual among prokaryotes. Chromosomes are distinguished from plasmids by the presence of essential genes as well as characteristic cell cycle-linked replication kinetics; unlike plasmids, chromosomes initiate replication once per cell cycle. The existence of multipartite prokaryotic genomes raises several questions regarding how multiple chromosomes are replicated and segregated during the cell cycle. These divided genomes also introduce questions regarding chromosome evolution and genome stability. In this review, we discuss these and other issues, with particular emphasis on the cholera pathogen Vibrio cholerae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04622.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Characterization of XerC- and XerD-dependent CTX phage integration in Vibrio cholerae (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 54 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: CTXφ is a filamentous bacteriophage that encodes cholera toxin and integrates site-specifically into the larger of the two Vibrio cholerae chromosomes. The CTXφ genome lacks an integrase; instead, its integration depends on the chromosome-encoded tyrosine recombinases XerC and XerD. During integration, recombination occurs between regions of homology in CTXφ and the V. cholerae chromosome. Here, we define the elements on the phage genome (attP ) and bacterial chromosome (attB) required for CTXφ integration. attB is a short sequence composed of one binding site for XerC and XerD spanning the site of recombination. Together, XerC and XerD bind to two sites within attP. While one XerC/D binding site in attP spans the core recombination region, the other site is ≈ 80 bp away. Although integration occurs at the core XerC/D binding site in attP, the second site is required for CTXφ integration, suggesting it performs an architectural role in the integration reaction. In vitro cleavage reactions showed that XerC and XerD are capable of cleaving attB and attP sequences; however, additional cellular processes such as DNA replication or Holliday junction resolution by a host resolvase may contribute to integration in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04309.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Hfq is essential for Vibrio cholerae virulence and downregulates σE expression (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Hfq is an RNA-binding protein that interacts with both small untranslated RNAs (sRNAs) and mRNAs to modulate gene expression post-transcriptionally. In Escherichia coli and Salmonella typhimurium, Hfq is required for efficient expression of the stationary phase sigma factor σS, and consequently is critical for Salmonella virulence. We have found that Hfq is also essential for the virulence of Vibrio cholerae, as strains lacking hfq fail to colonize the suckling mouse intestine. Deletion of the V. cholerae hfq does not prevent production of σS, nor does it prevent expression of TCP, V. cholerae's primary colonization factor. The expression and activity of the alternative sigma factor σE are dramatically increased in a V. cholerae hfq mutant. Comparison of the transcriptome of an hfq mutant with that of an rseA mutant, which also overexpresses σE, revealed that σE controls approximately half the genes found to be upregulated in the hfq mutant. However, increased σE does not appear to account for this strain's reduced virulence. It is likely that sRNAs, in conjunction with Hfq, are critical regulators of V. cholerae pathogenicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04142.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    CTXφ and Vibrio cholerae: exploring a newly recognized type of phage–host cell relationship (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 57 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genes encoding cholera toxin, one of the principal virulence factors of the diarrhoeal pathogen Vibrio cholerae, are part of the genome of CTXφ, a filamentous bacteriophage. Thus, CTXφ has played a critical role in the evolution of the pathogenicity of V. cholerae. Unlike the well-studied F pilus-specific filamentous coliphages, CTXφ integrates site-specifically into its host chromosome and forms stable lysogens. Here we focus on the CTXφ life cycle and, in particular, on recent studies of the mechanism of CTXφ integration and the factors that govern lysogeny. These and other processes illustrate the remarkable dependence of CTXφ on host-encoded factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04676.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...