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  • Exopolysaccharide biosynthesis  (2)
  • Sinorhizobium meliloti  (2)
  • Springer  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Biocontrol strain Pseudomonas fluorescens CHA0 and its genetically modified derivative with enhanced biocontrol capability exert comparable effects on the structure of a Sinorhizobium meliloti population in gnotobiotic systems (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 240-244 
    Details
    ISSN: 1432-0789
    Keywords: Key words Ecological impact ; Genetically modified ; organisms ; Microcosm studies ; Symbiotic nitrogen ; fixation ; Plant-beneficial bacteria ; Sinorhizobium meliloti
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The impact of biocontrol strain Pseudomonas fluorescens CHA0 and of its genetically modified, antibiotic-overproducing derivative CHA0/pME3424 on a reconstructed population of the plant-beneficial Sinorhizobium meliloti bacteria was assessed in gnotobiotic systems. In sterile soil, the final density of the reconstructed S. meliloti population decreased by more than one order of magnitude in the presence of either of the Pseudomonas strains when compared to a control without addition of P. fluorescens. Moreover, there was a change in the proportion of each individual S. meliloti strain within the population. Plant tests also revealed changes in the nodulating S. meliloti population in the presence of strains CHA0 or CHA0/pME3424. In both treatments one S. meliloti strain, f43, was significantly reduced in its root nodule occupancy. Analysis of alfalfa yields showed a slight but statistically significant increase in shoot dry weight when strain CHA0 was added to the reconstructed S. meliloti population whereas no such effect was observed with CHA0/pME3424.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050309
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  • 2
    Electronic Resource
    Electronic Resource
    Identification and analysis of the Rhizobium meliloti exoAMONP genes involved in exopolysaccharide biosynthesis and mapping of promoters located on the exoHKLAMONP fragment (1993)
    Springer
    Molecular genetics and genomics 241 (1993), S. 367-379 
    Details
    ISSN: 1617-4623
    Keywords: Rhizobium meliloti ; Exopolysaccharide biosynthesis ; UDP-glucose pyrophosphorylase ; Glucosyltransferase ; Promoter mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sequence analysis of a 7.494 kb DNA fragment from megaplasmid 2 of Rhizobium meliloti 2011 involved in exopolysaccharide I (EPS 1) biosynthesis revealed the presence of five exo genes designated exoA, exoM, exoN, exoO, and exoP. ExoN was found to show strong homology to a UDP-glucose pyrophosphorylase from Acetobacter xylinum, whereas ExoO displayed weak homologies to the NodC proteins from R. meliloti and R. loti. Supprisingly, different mutations in exoP resulted in divergent phenotypes. One exoP mutant was able to establish an effective symbiosis with alfalfa, although no EPS I polymer could be detected. In contrast, other exoP mutations prevented the formation of an effective symbiosis. The transcriptional organization of the exoA-exoP gene region has been analysed in conjunction with the exoH, exoK and exoL genes. Using exo-lacZ transcription fusions in association with plasmid integration mutagenesis a strong promoter was identified upstream of exoH, which is able to direct transcription of the whole exoHKLAMONP gene cluster. A much weaker promoter upstream of exoL was found to be involved in the transcription of the exoLAMONP genes. In addition, weak promoters were identified upstream of exoK, exoA, exoN and exoP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284690
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  • 3
    Electronic Resource
    Electronic Resource
    The Sinorhizobium meliloti MucR protein, which is essential for the production of high-molecular-weight succinoglycan exopolysaccharide, binds to short DNA regions upstream of exoH and exoY (1998)
    Springer
    Molecular genetics and genomics 257 (1998), S. 433-441 
    Details
    ISSN: 1617-4623
    Keywords: Key words Regulation of gene expression ; Sinorhizobium meliloti ; Rhizobium meliloti ; Exopolysaccharide biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sinorhizobium meliloti (Rhizobium meliloti) is able to produce two different exopolysaccharides, succinoglycan and galactoglucan. Mutations in the mucR gene of S. meliloti result in the stimulation of galactoglucan synthesis, while the type of succinoglycan produced is modified. In culture supernatants of a mucR mutant, low-molecular-weight succinoglycan is present, whereas no high-molecular-weight succinoglycan could be detected. The biosynthesis of succinoglycan is directed by the products of the exo gene cluster. Two DNA fragments from this cluster, one located in front of the exoH gene and one in the intergenic region between the divergently transcribed genes exoX and exoY, were shown to represent effective binding sites for MucR. Whereas the latter binding site contains an inverted repeat motif, the former does not. However, the binding of MucR did not strongly modify the transcription of the exo genes involved. In the mucR mutant the expression levels of exoH-lacZ and exoX-lacZ transcriptional fusions were found to be increased 1.5- and 1.7-fold, respectively. On the other hand, the expression level of an exoY-lacZ transcriptional fusion was found to be 1.5-fold lower in the mucR mutant than in the wild-type background. Comparison of the DNA sequences of MucR-binding sites provides insight into the structural requirements for binding of MucR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380050667
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