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  • 1
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    Online Resource
    Essential Components of the Ti Plasmidtrb System, a Type IV Macromolecular Transporter
    American Society for Microbiology ; 1999
    In:  Journal of Bacteriology Vol. 181, No. 16 ( 1999-08-15), p. 5033-5041
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 181, No. 16 ( 1999-08-15), p. 5033-5041
    Abstract: The trb operon from pTiC58 is one of three loci that are required for conjugal transfer of this Ti plasmid. The operon, which probably codes for the mating bridge responsible for pair formation and DNA transfer, contains 12 genes, 11 of which are related to genes from other members of the type IV secretion system family. The 12th gene, traI , codes for production of Agrobacterium autoinducer (AAI). Insertion mutations were constructed in each of the 12 genes, contained on a full-length clone of the trb region, using antibiotic resistance cassettes or a newly constructed transposon. This transposon, called mini-Tn 5 P trb , was designed to express genes downstream of the insertion site from a promoter regulated by TraR and AAI. Each mutation could trans complement downstream Tn 3 HoHo1 insertions in the trb operon of full-sized Ti plasmids. When marker-exchanged into the transfer-constitutive Ti plasmid pTiC58Δ accR mutations in trbB , - C , - D , - E , - L , - F , - G , and - H abolished conjugal transfer from strain UIA5, which lacks the 450-kb catabolic plasmid pAtC58. However, these mutants retained residual conjugal transfer activity when tested in strain NT1, which contains this large plasmid. The trbJ mutant failed to transfer at a detectable frequency from either strain, while the trbI mutant transferred at very low but detectable levels from both donors. Only the trbK mutant was unaffected in conjugal transfer from either donor. Transfer of each of the marker-exchange mutants was restored by a clone expressing only the wild-type allele of the corresponding mutant trb gene. An insertion mutation in traI abolished the production of AAI and also conjugal transfer. This defect was restored by culturing the mutant donor in the presence of AAI. We conclude that all of the trb genes except trbI and trbK are essential for conjugal transfer of pTiC58. We also conclude that mutations in any one of the trb genes except traI and trbJ can be complemented by functions coded for by pAtC58.
    Type of Medium: Online Resource
    ISSN: 1098-5530 , 0021-9193
    URL: Article
    DOI: 10.1128/JB.181.16.5033-5041.1999
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1999
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 2
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    Online Resource
    Bases of biocontrol: Sequence predicts synthesis and mode of action of agrocin 84, the Trojan Horse antibiotic that controls crown gall
    Proceedings of the National Academy of Sciences ; 2006
    In:  Proceedings of the National Academy of Sciences Vol. 103, No. 23 ( 2006-06-06), p. 8846-8851
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 103, No. 23 ( 2006-06-06), p. 8846-8851
    Abstract: Agrobacterium radiobacter K84, used worldwide to biocontrol crown gall disease caused by Agrobacterium tumefaciens , produces an antiagrobacterial compound called agrocin 84. We report the nucleotide sequence of pAgK84, a 44.42-kb plasmid coding for production of this disubstituted adenine nucleotide antibiotic. pAgK84 encodes 36 ORFs, 17 of which ( agn ) code for synthesis of or immunity to agrocin 84. Two genes, agnB2 and agnA , encode aminoacyl tRNA synthetase homologues. We have shown that the toxic moiety of agrocin 84 inhibits cellular leucyl-tRNA synthetases and AgnB2, which confers immunity to the antibiotic, is a resistant form of this enzyme. AgnA, a truncated homologue of asparaginyl tRNA synthetase could catalyze the phosphoramidate bond between a precursor of the methyl pentanamide side group and the nucleotide. We propose previously undescribed chemistry, catalyzed by AgnB1, to generate the precursor necessary for this phosphoramidate linkage. AgnC7 is related to ribonucleotide reductases and could generate the 3′-deoxyarabinose moiety of the nucleoside. Bioinformatics suggest that agnC3 , agnC4 , and agnC6 contribute to maturation of the methyl pentanamide, whereas agnC2 may produce the glucofuranose side group bound to the adenine ring. AgnG is related to bacterial exporters. An agnG mutant accumulated agrocin 84 intracellularly but did not export the antibiotic. pAgK84 is transmissible and encodes genes for conjugative DNA processing but lacks a type IV secretion system, suggesting that pAgK84 transfers by mobilization. By sequence analysis, the deletion engineered into pAgK1026 removed the oriT and essential tra genes, confirming the enhanced environmental safety of this modified form of pAgK84.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0602965103
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2006
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 3
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    Modulating quorum sensing by antiactivation: TraM interacts with TraR to inhibit activation of Ti plasmid conjugal transfer genes
    Wiley ; 1999
    In:  Molecular Microbiology Vol. 34, No. 2 ( 1999-10), p. 282-294
    Details
    In: Molecular Microbiology, Wiley, Vol. 34, No. 2 ( 1999-10), p. 282-294
    Type of Medium: Online Resource
    ISSN: 0950-382X , 1365-2958
    URL: Article
    DOI: 10.1046/j.1365-2958.1999.01595.x
    Language: English
    Publisher: Wiley
    Publication Date: 1999
    detail.hit.zdb_id: 1501537-3
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  • 4
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    Hierarchical gene regulatory systems arising from fortuitous gene associations: controlling quorum sensing by the opine regulon in Agrobacterium
    Wiley ; 1999
    In:  Molecular Microbiology Vol. 32, No. 5 ( 1999-06), p. 1077-1089
    Details
    In: Molecular Microbiology, Wiley, Vol. 32, No. 5 ( 1999-06), p. 1077-1089
    Abstract: Conjugation of the Agrobacterium Ti plasmid pTiC58 is regulated by a hierarchy involving induction by the opines agrocinopines A and B and a quorum‐sensing system. Regulation by the opines is mediated by the repressor AccR, while quorum sensing is effected by the transcriptional activator TraR and its ligand, the acyl‐homoserine lactone signal molecule Agrobacterium autoinducer (AAI). These last two elements combine to activate expression of the tra system at high population densities. Sequence analysis indicated that traR is the fourth gene of an operon, which we named arc , that is transcribed divergently from accR . Complementation analysis of mutations in the genes 5′ to traR showed that the other members of the arc operon are not required for conjugation. Analysis of lacZ reporter fusions demonstrated that traR expression is regulated directly by AccR. Deletion analysis showed that AccR‐regulated expression of traR initiates from a promoter located in the intergenic region between accR and orfA , the first gene of the arc operon. Reverse transcriptase–polymerase chain reaction (RT–PCR) and primer extension analyses indicated that the arc transcript initiates upstream of orfA and proceeds uninterrupted through traR . These results are consistent with a model in which quorum sensing is subordinate to the opine regulon because traR has become associated with an operon controlled by the opine‐responsive transcriptional regulator.
    Type of Medium: Online Resource
    ISSN: 0950-382X , 1365-2958
    URL: Article
    DOI: 10.1046/j.1365-2958.1999.01422.x
    Language: English
    Publisher: Wiley
    Publication Date: 1999
    detail.hit.zdb_id: 1501537-3
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