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  • Springer  (3)
  • Blackwell Publishing Ltd  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Characterization of flaA− and flaB− mutants of Serpulina hyodysenteriae: both flagellin subunits, FlaA and FlaB, are necessary for full motility and intestinal colonization (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 153 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Motility of Serpulina hyodysenteriae is thought to play a pivotal role in the enteropathogenicity of this spirochete. To test this, a series of isogenic mutants containing specifically disrupted flagellar alleles (flaA1 and flaB1) were constructed and examined for virulence and ability to colonize the intestinal tract of mice. Mice challenged with the wild-type, parent strain showed a dose-related response to the challenge organism. In contrast, all flagellar mutant strains demonstrated aberrant motility in vitro and a significantly reduced ability to colonize and infect mice. To some extent, this degree of reduction in colonizing ability was dependent on the wild-type background strain used for mutant construction. A flaB1− strain generated from a ‘laboratory isolate’ was unable to colonize the mouse gut even at high challenge doses, although its parent was virulent for mice. However, when the same parent strain was ‘animal-passeD’ prior to disruption of flaB1, the resulting flaB1− strain was able to transiently colonize the mouse gut and induce intestinal lesions. A comparison of a series of flagellar mutants constructed using the animal-passed parent strain further revealed that specific inactivation of flaB1 resulted in a more pronounced reduction in virulence and colonizing ability than that which occurred with two flaA1 mutants. Taken together, these data suggest that motility is an essential virulence factor of S. hyodysenteriae and that both sheath and core flagellin subunits, FlaA and FlaB, are necessary for full motility and intestinal colonization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb10472.x
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Variation in adhesion and cell surface hydrophobicity in Candida albicans white and opaque phenotypes (1988)
    Springer
    Mycopathologia 102 (1988), S. 149-156 
    Details
    ISSN: 1573-0832
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A previous study had established that a select group of pathogenic isolates of Candida albicans was capable of switching heritably, reversibly and at a high frequency (10−2 to 10−3) between two phenotypes (‘white’ or ‘opaque’) readily distinguishable by the size, shape, and color of colonies formed on agar at 25°C. This paper describes experiments designed to determine the ability of these two phenotypes to attach to buccal epithelial cells (BECs) and plastic, and to compare the cell surface hydrophobicities of white and opaque phenotypes from three clinical isolates. ‘White cells’ were found to be significantly more adhesive to BECs, and a strong correlation was also found between phenotype adhesiveness and the percentage of BECs to which C. albicans had attached. The percentage of BECs with one or more attached C. albicans was approximately 90% for the white phenotype and approximately 50% for the opaque phenotype. ‘Opaque cells’, in contrast, were twice as hydrophobic as white cells, and the percentage of opaque cells bound to BECs by coadhesion was also double that of white cells. The differences in adhesion to plastic between the two phenotypes were not statistically significant and there was no distinct trend to suggest which phenotype might be more adhesive to plastic. These results indicate that several factors are involved in the adhesion of C. albicans to plastic, and confirm the hypothesis that cell surface hydrophobicity is of minor importance in direct adhesion to epithelial cells but that it may contribute to indirect attachment to epithelial cells by promoting yeast coadhesion. Moreover, the data presented in this paper also revealed that under identical growth conditions, adhesion of C. albicans was significantly altered depending on the phenotypic state of the organism tested. Therefore, because C. albicans can switch at a high frequency to various phenotypes in vitro, it may be that in future adhesion studies involving Candida the phenotypic state of the organism at the time of testing will have to be determined. Otherwise, the results, even within the same laboratory, may be difficult to interpret.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00437397
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    An anaerobic continuous-flow culture model of interactions between intestinal microflora and Candida albicans (1988)
    Springer
    Mycopathologia 103 (1988), S. 125-134 
    Details
    ISSN: 1573-0832
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The finding by earlier workers that Escherichia coli suppressed the growth of Candida albicans in vitro or in gnotobiotic mice has led to numerous, erroneous conclusions regarding the identity of the organisms and mechanisms responsible for the suppression of Candida in the gut. This is due, in part, to the fact that nearly all studies to date have not reflected interactions as they occur in the intestinal tract. This paper describes a series of experiments that establish that an anaerobic continuous-flow (CF) culture model, of the ecology of the large intestinal flora reproduces interactions between bacteria and Candida as they occur in the large intestine. This was determined in the following ways. (i) Bacterial counts in CF cultures of conventional mouse cecal flora or human fecal flora closely resembled that found in the mouse intestine and human feces. (ii) Dense layers of bacterial growth that formed on the glass walls of the CF culture vessels resembled bacterial populations that colonize intestinal mucosa. (iii) Total and individual levels of certain metabolic end-products of the predominant anaerobic bacterial flora present in CF cultures coincided with those found in the large intestine of conventional mice or human feces used to establish the CF cultures. (iv) C. albicans was eliminated from CF cultures of mouse cecal flora at a rate similar to that of untreated experimental animals. (v) Contents of CF cultures fed to antibiotic-treated mice redressed several cecal abnormalities, and suppressed Candida populations to levels found in conventional animals. Thus, a number of complex ecological mechanisms were maintained in CF cultures which normally control Candida populations in the large intestine. It is suggested, therefore, that the CF culture model should help to further define the mechanisms which control C. albicans and other fungi in the intestinal tract, as well as define which components of the indigenous microflora are responsible for suppression of Candida in the gut.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00436810
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Absence of persistence and transfer of genetic material by recombinantEscherichia coli in conventional, antibiotic-treated mice (1993)
    Springer
    Journal of industrial microbiology and biotechnology 11 (1993), S. 259-271 
    Details
    ISSN: 1476-5535
    Schlagwort(e): Environmental assessment ; Bovine somatotropin ; Persistence ; Gene transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Strain BST-1 is a derivative ofEscherichia coli K-12 that carries a plasmid designated pURA-4 and is the expression system used by The Upjohn Company in the production of recombinant bovine somatotropin (rbSt). This plasmid also encodes an ampicillin resistance gene. The plasmidless carrier strain, BST-1C, contains a gene for tetracycline resistance which is provided by the chromosomal insertion of the transposon Tn10. Therefore, BST-1 is resistant to ampicillin and tetracycline, while BST-1C is resistant only to tetracycline. The Food and Drug Administration requested that we conduct an environmental assessment study to monitor the ‘persistence of the recombinant live K-12E. coli organism compared to the hostE. coli organism’. In addition, we were requested to monitor ‘the potential transfer of genetic material from (our) recombinant organism to the indigenous microflora’ of the mouse gastrointestinal (GI) tract. The differences in persistence were determined by monitoring shedding of BST-1 and BST-1C in the feces of conventionally reared, outbred mice inoculated with either of the two strains. Even with antibiotic selective pressure applied (tetracycline in the water), BST-1 did not persist as well as the non-plasmid carrying parental stain, BST-1C. In the gene transfer experiments, transfer of pURA-4 was monitored by the appearance of the ampicillin resistance marker and/or by hybridization assays for the rbSt gene in indigenous, mouse-colonizingE. coli strains which had been made streptomycin resistant. At the limit of detection, no transfer of pURA-4 was detected either in vitro or in vivo. These data support an interpretation that BST-1 does not present an environmental hazard as measured by colonization/persistence in the gut of conventionally reared mammals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01569599
    Standort Signatur Erwartet Verfügbarkeit
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