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  • 1
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 64, No. 9 ( 1998-09), p. 3180-3187
    Kurzfassung: Plant-pathogenic bacteria produce various extracellular polysaccharides (EPSs) which may function as virulence factors in diseases caused by these bacteria. The EPS levan is synthesized by the extracellular enzyme levansucrase in Pseudomonas syringae , Erwinia amylovora , and other bacterial species. The lsc genes encoding levansucrase from P. syringae pv. glycinea PG4180 and P. syringae pv. phaseolicola NCPPB 1321 were cloned, and their nucleotide sequences were determined. Heterologous expression of the lsc gene in Escherichia coli was found in four and two genomic library clones of strains PG4180 and NCPPB 1321, respectively. A 3.0-kb Pst I fragment common to all six clones conferred levan synthesis on E. coli when further subcloned. Nucleotide sequence analysis revealed a 1,248-bp open reading frame (ORF) derived from PG4180 and a 1,296-bp ORF derived from NCPPB 1321, which were both designated lsc . Both ORFs showed high homology to the E. amylovora and Zymomonas mobilis lsc genes at the nucleic acid and deduced amino acid sequence levels. Levansucrase was not secreted into the supernatant but was located in the periplasmic fraction of E. coli harboring the lsc gene. Expression of lsc was found to be dependent on the vector-based P lac promoter, indicating that the native promoter of lsc was not functional in E. coli . Insertion of an antibiotic resistance cassette in the lsc gene abolished levan synthesis in E. coli . A PCR screening with primers derived from lsc of P. syringae pv. glycinea PG4180 allowed the detection of this gene in a number of related bacteria.
    Materialart: Online-Ressource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 1998
    ZDB Id: 223011-2
    ZDB Id: 1478346-0
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2012
    In:  Applied and Environmental Microbiology Vol. 78, No. 19 ( 2012-10), p. 6900-6907
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 78, No. 19 ( 2012-10), p. 6900-6907
    Kurzfassung: Alga-bacterium interactions are crucial for aggregate formation and carbon cycling in aquatic systems. To understand the initiation of these interactions, we investigated bacterial chemotaxis within a bilateral model system. Marinobacter adhaerens HP15 has been demonstrated to attach to the diatom Thalassiosira weissflogii and induce transparent exopolymeric particle and aggregate formation. M. adhaerens possesses one polar flagellum and is highly motile. Bacterial cells were attracted to diatom cells, as demonstrated by addition of diatom cell homogenate or diatom culture supernatant to soft agar, suggesting that chemotaxis might be important for the interaction of M. adhaerens with diatoms. Three distinct chemotaxis-associated gene clusters were identified in the genome sequence of M. adhaerens , with the clusters showing significant sequence similarities to those of Pseudomonas aeruginosa PAO1. Mutations in the genes cheA , cheB , chpA , and chpB , which encode histidine kinases and methylesterases and which are putatively involved in either flagellum-associated chemotaxis or pilus-mediated twitching motility, were generated and mutants with the mutations were phenotypically analyzed. Δ cheA and Δ cheB mutants were found to be swimming deficient, and all four mutants were impaired in biofilm formation on abiotic surfaces. Comparison of the HP15 wild type and its chemotaxis mutants in cocultures with the diatom revealed that the fraction of bacteria attaching to the diatom decreased significantly for mutants in comparison to that for the wild type. Our results highlight the importance of M. adhaerens chemotaxis in initiation of its interaction with the diatom. In-depth knowledge of these basic processes in interspecies interactions is pivotal to obtain a systematic understanding of organic matter flux and nutrient cycling in marine ecosystems.
    Materialart: Online-Ressource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2012
    ZDB Id: 223011-2
    ZDB Id: 1478346-0
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    Canadian Science Publishing ; 2006
    In:  Canadian Journal of Microbiology Vol. 52, No. 5 ( 2006-05-01), p. 468-475
    In: Canadian Journal of Microbiology, Canadian Science Publishing, Vol. 52, No. 5 ( 2006-05-01), p. 468-475
    Kurzfassung: Genes involved in pathogenicity of several plant pathogens were shown to be induced at relatively cold temperatures. Loci from the fire blight pathogen Erwinia amylovora (Burrill) induced at 18 °C were identified using the miniTn5 transposon that contains the promoterless reporter gene gusA coding for β-glucuronidase (GUS). Certain mutants (2.7%) expressed GUS predominantly at 18 °C on minimal medium plates, indicating that the transposon had been inserted downstream of a putatively thermoregulated promoter. Those mutants were further screened with a quantitative GUS fluorometric assay. A total of 21 mutants were selected: 19 mutants had a transposon insertion in temperature-dependent genetic loci, with a 2.2- to 6.3-fold induction of gusA gene expression at 18 °C, and two mutants with impaired growth at 18 °C. Some of these genetic loci encoded (i) proteins implicated in flagella biosynthesis, biotin biosynthesis, multi-drug efflux, and type II secretion protein, and (ii) proteins of unknown function.Key words: fire blight, Erwinia amylovora, transposon mutagenesis, gene regulation, low temperature.
    Materialart: Online-Ressource
    ISSN: 0008-4166 , 1480-3275
    RVK:
    Sprache: Englisch
    Verlag: Canadian Science Publishing
    Publikationsdatum: 2006
    ZDB Id: 280534-0
    ZDB Id: 1481972-7
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2008
    In:  Applied and Environmental Microbiology Vol. 74, No. 11 ( 2008-06), p. 3387-3393
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 74, No. 11 ( 2008-06), p. 3387-3393
    Kurzfassung: In gram-negative bacteria, transporters belonging to the RND family are the transporters most relevant for resistance to antimicrobial compounds. In Pseudomonas aeruginosa , a clinically important pathogen, the RND-type pump MexAB-OprM has been recognized as one of the major multidrug efflux systems. Here, homologues of MexAB-OprM in the plant pathogens Pseudomonas syringae pv. phaseolicola 1448A, P. syringae pv. syringae B728a, and P. syringae pv. tomato DC3000 were identified, and mexAB-oprM -deficient mutants were generated. Determination of MICs revealed that mutation of MexAB-OprM dramatically reduced the tolerance to a broad range of antimicrobials. Moreover, the ability of the mexAB - oprM -deficient mutants to multiply in planta was reduced. RNA dot blot hybridization revealed growth-dependent regulation of the mexAB-oprM operon in P. syringae ; the expression of this operon was maximal in early exponential phase and decreased gradually during further growth.
    Materialart: Online-Ressource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2008
    ZDB Id: 223011-2
    ZDB Id: 1478346-0
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    American Society for Microbiology ; 2004
    In:  Applied and Environmental Microbiology Vol. 70, No. 2 ( 2004-02), p. 693-703
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 70, No. 2 ( 2004-02), p. 693-703
    Kurzfassung: 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.
    Materialart: Online-Ressource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2004
    ZDB Id: 223011-2
    ZDB Id: 1478346-0
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 76, No. 9 ( 2010-05), p. 2704-2711
    Kurzfassung: The use of naturally occurring microbial antagonists to suppress plant diseases offers a favorable alternative to classical methods of plant protection. The soybean epiphyte Pseudomonas syringae pv. syringae strain 22d/93 shows great potential for controlling P. syringae pv. glycinea, the causal agent of bacterial blight of soybean. Its activity against P. syringae pv. glycinea is highly reproducible even in field trials, and the suppression mechanisms involved are of special interest. In this work we demonstrated that P . syringae pv. syringae 22d/93 produced a significantly larger amount of siderophores than the pathogen P. syringae pv. glycinea produced. While P . syringae pv. syringae 22d/93 and P. syringae pv. glycinea produce the same siderophores, achromobactin and pyoverdin, the regulation of siderophore biosynthesis in the former organism is very different from that in the latter organism. The epiphytic fitness of P . syringae pv. syringae 22d/93 mutants defective in siderophore biosynthesis was determined following spray inoculation of soybean leaves. The population size of the siderophore-negative mutant P . syringae pv. syringae strain 22d/93ΔSid was 2 orders of magnitude lower than that of the wild type 10 days after inoculation. The growth deficiency was compensated for when wound inoculation was used, indicating the availability of iron in the presence of small lesions on the leaves. Our results suggest that siderophore production has an indirect effect on the biocontrol activity of P . syringae pv. syringae 22d/93. Although siderophore-defective mutants of P . syringae pv. syringae 22d/93 still suppressed development of bacterial blight caused by P. syringae pv. glycinea, siderophore production enhanced the epiphytic fitness and thus the competitiveness of the antagonist.
    Materialart: Online-Ressource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Sprache: Englisch
    Verlag: American Society for Microbiology
    Publikationsdatum: 2010
    ZDB Id: 223011-2
    ZDB Id: 1478346-0
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    In: Journal of Phycology, Wiley, Vol. 55, No. 6 ( 2019-12), p. 1246-1257
    Kurzfassung: Microalgae are a promising resource for the highly sustainable production of various biomaterials (food and feed), high‐value biochemicals, or biofuels. However, factors influencing the valued lipid production from oleaginous algae require a more detailed investigation. This study elucidates the variations in lipid metabolites between a marine diatom ( Cylindrotheca closterium ) and a freshwater green alga ( Scenedesmus sp.) under nitrogen starvation at the molecular species level, with emphasis on triacylglycerols using liquid chromatography–electrospray ionization mass spectrometry techniques. A comprehensive analysis was carried out by comparing the changes in total lipids, growth kinetics, fatty acid compositions, and glycerolipid profiles at the molecular species level at different time points of nitrogen starvation. A total of 60 and 72 triacylglycerol molecular species, along with numerous other polar lipids, were identified in Scenedesmus sp. and C. closterium , respectively, providing the most abundant triacylglycerol profiles for these two species. During nitrogen starvation, more triacylglycerol of Scenedesmus sp. was synthesized via the “eukaryotic pathway” in the endoplasmic reticulum, whereas the increase in triacylglycerol in C. closterium was mainly a result of the “prokaryotic pathway” in the chloroplasts after 96 h of nitrogen starvation. The distinct responses of lipid synthesis to nitrogen starvation exhibited by the two species indicate different strategies of lipid accumulation, notably triacylglycerols, in green algae and diatoms. Scenedesmus sp. and Cylindrotheca closterium could serve as excellent candidates for the mass production of biofuels or polyunsaturated fatty acids for nutraceutical purposes.
    Materialart: Online-Ressource
    ISSN: 0022-3646 , 1529-8817
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2019
    ZDB Id: 281226-5
    ZDB Id: 1478748-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    In: FEMS Microbiology Letters, Oxford University Press (OUP), Vol. 265, No. 2 ( 2006-12), p. 178-185
    Materialart: Online-Ressource
    ISSN: 0378-1097 , 1574-6968
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2006
    ZDB Id: 1501716-3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Online-Ressource
    Online-Ressource
    Oxford University Press (OUP) ; 2008
    In:  FEMS Microbiology Letters Vol. 283, No. 2 ( 2008-04-21), p. 231-238
    In: FEMS Microbiology Letters, Oxford University Press (OUP), Vol. 283, No. 2 ( 2008-04-21), p. 231-238
    Materialart: Online-Ressource
    ISSN: 0378-1097 , 1574-6968
    URL: Issue
    RVK:
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2008
    ZDB Id: 1501716-3
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    Online-Ressource
    Online-Ressource
    Springer Science and Business Media LLC ; 2015
    In:  Antonie van Leeuwenhoek Vol. 108, No. 3 ( 2015-9), p. 649-658
    In: Antonie van Leeuwenhoek, Springer Science and Business Media LLC, Vol. 108, No. 3 ( 2015-9), p. 649-658
    Materialart: Online-Ressource
    ISSN: 0003-6072 , 1572-9699
    RVK:
    Sprache: Englisch
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2015
    ZDB Id: 1478112-8
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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