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  • Weingart, Helge  (3)
  • 2000-2004  (3)
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  • 2000-2004  (3)
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  • 1
    Online Resource
    Online Resource
    NorM, an Erwinia amylovora Multidrug Efflux Pump Involved in In Vitro Competition with Other Epiphytic Bacteria
    American Society for Microbiology ; 2004
    In:  Applied and Environmental Microbiology Vol. 70, No. 2 ( 2004-02), p. 693-703
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 70, No. 2 ( 2004-02), p. 693-703
    Abstract: Blossoms are important sites of infection for Erwinia amylovora , the causal agent of fire blight of rosaceous plants. Before entering the tissue, the pathogen colonizes the stigmatic surface and has to compete for space and nutrient resources within the epiphytic community. Several epiphytes are capable of synthesizing antibiotics with which they antagonize phytopathogenic bacteria. Here, we report that a multidrug efflux transporter, designated NorM, of E. amylovora confers tolerance to the toxin(s) produced by epiphytic bacteria cocolonizing plant blossoms. According to sequence comparisons, the single-component efflux pump NorM is a member of the multidrug and toxic compound extrusion protein family. The corresponding gene is widely distributed among E. amylovora strains and related plant-associated bacteria. NorM mediated resistance to the hydrophobic cationic compounds norfloxacin, ethidium bromide, and berberine. A norM mutant was constructed and exhibited full virulence on apple rootstock MM 106. However, it was susceptible to antibiotics produced by epiphytes isolated from apple and quince blossoms. The epiphytes were identified as Pantoea agglomerans by 16S rRNA analysis and were isolated from one-third of all trees examined. The promoter activity of norM was twofold greater at 18°C than at 28°C. The lower temperature seems to be beneficial for host infection because of the availability of moisture necessary for movement of the pathogen to the infection sites. Thus, E. amylovora might employ NorM for successful competition with other epiphytic microbes to reach high population densities, particularly at a lower temperature.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.70.2.693-703.2004
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Impact of Temperature on In Planta Expression of Genes Involved in Synthesis of the Pseudomonas syringae Phytotoxin Coronatine
    Scientific Societies ; 2004
    In:  Molecular Plant-Microbe Interactions® Vol. 17, No. 10 ( 2004-10), p. 1095-1102
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 17, No. 10 ( 2004-10), p. 1095-1102
    Abstract: Coronatine (COR) is a chlorosis-inducing phytotoxin produced by the plant-pathogenic bacterium Pseudomonas syringae. Confocal laser scanning microscopy was used to investigate in vitro and in planta expression of COR genes by two model organisms, P. syringae pv. glycinea PG4180, a pathogen of soybean, and P. syringae pv. tomato DC3000, a pathogen of tomato and crucifers. Previously, it was shown in vitro that the cma operon involved in COR synthesis in PG4180 is expressed in a temperature-dependent manner, with maximal rates at 18°C and low activity at 28°C. However, nothing was known about the influence of temperature on the expression of COR biosynthetic genes in planta. Therefore, transcriptional fusions of the PG4180 and DC3000 cma promoter regions to a promoterless egfp gene were constructed and expressed in both P. syringae strains. The fluorescence patterns in response to temperature during growth of a strain in vitro were consistent with its COR production and the cma transcript abundance as revealed by RNA dot blot hybridization. Quantification of fluorescence indicated that cma promoter activity was dependent on the genetic background of the host strain. Expression of cma∷egfp in PG4180 was temperature-dependent in minimal medium as well as inside the plant tissue. In contrast, transcription of the cma operon was not significantly affected by temperature in DC3000. However, cells of DC3000 harboring the cma∷egfp fusions showed higher levels of fluorescence when recovered from infected host plants compared with cells grown in minimal medium. These results indicate that the signals for induction of COR biosynthesis differ significantly in PG4180 and DC3000.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2004.17.10.1095
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2004
    detail.hit.zdb_id: 2037108-1
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    The Phytoalexin-Inducible Multidrug Efflux Pump AcrAB Contributes to Virulence in the Fire Blight Pathogen, Erwinia amylovora
    Scientific Societies ; 2004
    In:  Molecular Plant-Microbe Interactions® Vol. 17, No. 1 ( 2004-01), p. 43-54
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 17, No. 1 ( 2004-01), p. 43-54
    Abstract: The enterobacterium Erwinia amylovora causes fire blight on members of the family Rosaceae, with economic importance on apple and pear. During pathogenesis, the bacterium is exposed to a variety of plant-borne antimicrobial compounds. In plants of Rosaceae, many constitutively synthesized isoflavonoids affecting microorganisms were identified. Bacterial multidrug efflux transporters which mediate resistance toward structurally unrelated compounds might confer tolerance to these phytoalexins. To prove this hypothesis, we cloned the acrAB locus from E. amylovora encoding a resistance nodulation division-type transport system. In Escherichia coli, AcrAB of E. amylovora conferred resistance to hydrophobic and amphiphilic toxins. An acrB-deficient E. amylovora mutant was impaired in virulence on apple rootstock MM 106. Furthermore, it was susceptible toward extracts of leaves of MM 106 as well as to the apple phytoalexins phloretin, naringenin, quercetin, and (+)-catechin. The expression of acrAB was determined using the promoterless reporter gene egfp. The acrAB operon was up-regulated in vitro by the addition of phloretin and naringenin. The promoter activity of acrR, encoding a regulatory protein involved in acrAB expression, was increased by naringenin. In planta, an induction of acrAB was proved by confocal laser scanning microscopy. Our results strongly suggest that the AcrAB transport system plays an important role as a protein complex required for virulence of E. amylovora in resistance toward apple phytoalexins and that it is required for successful colonization of a host plant.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2004.17.1.43
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2004
    detail.hit.zdb_id: 2037108-1
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
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