Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The uropathogenic Gram-negative bacterium Proteus mirabilis exhibits a form of multicellular behaviour termed swarming, which involves cyclical differentiation of typical vegetative cells into filamentous, multi-nucleate, hyperflagellate swarm cells capable of rapid and co-ordinated population migration across surfaces. We observed that differentiation into swarm cells was accompanied by substantial increases in the activities of intracellular urease and extracellular haemolysjn and metalloprotease, which are believed to be central to the pathogenicity of P. mirabills. In addition, the ability of P. mirabilis to invade human urothelial cells in vitro was primarily a characteristic of differentiated swarm cells, not vegetative cells. These virulence factor activities fell back as the cells underwent cyclical reversion to the vegetative form (consolidation), in parallel with the diagnostic modulation of flagellin levels on the cell surface. Control cellular alkaline phosphatase activities did not increase during differentiation or consolidation. Non-flagellated, non-motile transposon insertion mutants were unable to invade urothelial cells and they generated only low-level activities of haemolysin, urease and protease (0–10% of wild type). Motile mutants unable to differentiate into swarm cells were comparably reduced in their haemolytic, ureolytic and invasive phenotypes and generated threefold less protease activity. Mutants that were able to form swarm cells but exhibited various aberrant patterns of swarming migration produced wild-type activities of haemotysin, urease and protease, but their ability to enter urothelial cells was three- to 10-fold lower. Analysis of haemolysin (hpmA) transcripts showed that during swarm cell differentiation there was a c. 50-fold increase in the level of the predicted major 5.2 kb and minor 6.9 kb mRNAs transcribed from the hpm operon, and assay of mRNA complimentary to urease (ureC) and flagellin (fliC) gene sequences confirmed that modulation of virulence factor activity during the swarming cycle resulted from differential expression of virulence genes in parallel with fliC gene expression. Hybridization of stage-specific mRNA with 30 random, non-overlapping chromosomal gene probes provided no evidence for universal changes in the expression of the P. mirabiis genome, suggesting that differential virulence gene expression may be a specific strategy.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Swarming by Proteus mirabilis is characterized by cycles of rapid population migration across surfaces, following differentiation of typical vegetative rods into long, hyperflagellated, virulent swarm cells. A swarm-defective TnphoA insertion mutant was isolated that was not defective in cell motility, differentiation or control of the migration cycle, but was specifically impaired in the ability to undergo surface translocation as a multicellular mass. The mutation, previously shown to compromise urinary tract virulence, was located within a 1112 bp gene that restored normal swarming of the mutant when expressed in trans. The gene encoded a 40.6 kDa protein that is related to putative sugar transferases required for lipopolysaccharide (LPS) core modification in Shigella and Salmonella. The immediately distal open reading frame encoded a protein that is related to dehydrogenases involved in the synthesis of LPS O-side-chains, enterobacterial common antigen and extracellular polysaccharide (PS). Gel electrophoresis and electron microscopy showed that the mutant still made LPS but it had lost the ability to assemble a surface (capsular) PS, which gas-liquid chromatography and mass spectrometry indicated to be an acidic type II molecule rich in galacturonic acid and galactosamine. We suggest that this surface PS facilitates translocation of differentiated cell populations by reducing surface friction.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] When colonies differ in queen number, those with the fewest queens will have the most full-sister relationships, so workers in these colonies are predicted to rear females. Males should be reared in colonies with larger numbers of queens (Fig. 1). When queens are natal nestmates, this selfish ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 344 (1990), S. 388-388 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1615-6110
    Keywords: Leguminosae ; Mimoseae ; Leucaena ; Phylogeny ; chloroplast DNA ; polyploidy ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloroplast DNA restriction fragment length polymorphisms have been used to reconstruct the maternal phylogeny of all the known taxa in the small neotropical legume genusLeucaena. Three major plastome clades were recognized, but these did not conform with relationships between the taxa proposed on other characters from morphology, cytology or hybridization. The maternal parentage of tetraploids within the genus has been proposed. Evidence for introgression was found between “diploid”L. diversifolia and “tetraploid”L. diversifolia. The implications of these results for the origin of the cultivated taxa are discussed.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1615-6110
    Keywords: Leguminosae ; Parkinsonia aculeata ; Cercidium praecox ; Parkinsonia ×carterae ; Hybridization ; morphometric analysis ; cytology ; weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Morphometric, cytogenetic, geographical and ecological evidence for hybridization betweenParkinsonia aculeata andCercidium praecox is presented. Morphometric investigation using the character count procedure and cytogenetic observations confirm hybrid status. All diagnostic morphometric characters were intermediate in the hybrid. Both parents (2n = 28) show regular tetrad formation and pollen fertility greater than 94%. Hybrids have a chromosome number of 2n = 28 or 2n = 30, and display meiotic abnormalities including lagging chromosomes and micronucleus formation; less than 21% of hybrid pollen was fertile. Ecological and geographical information suggests that hybridization is occurring at increasing frequency due to the expanding range ofP. aculeata associated with cultivation as an ornamental, coupled with ecological disturbance and weediness, and the cultivation ofC. praecox and hybrids as fodder, ornamental and shade trees. Hybrid fertility and phenological observations, in conjunction with F-weighted principal component analysis, suggest that the progeny of F1 hybrids are established. The hybrid is formally described asP. ×carterae.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1615-6110
    Keywords: Leguminosae ; Leucaena leucocephala ; L. diversifolia ; L. ×spontanea ; Hybridization ; hybrid detection ; spontaneous hybrid ; RAPD ; RFLP ; chloroplast DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The detection of hybridity inLeucaena is discussed in relation to: (i) traditional criteria, (ii) molecular criteria and (iii) models to predict hybrid leaf morphology. Morphological, geographical and molecular evidence for the occurrence of interspecific hybrids betweenL. leucocephala andL. diversifolia in south-central Mexico, northern Guatemala, Jamaica, Dominican Republic, the Philippines and Papua New Guinea is presented. Predicted mean hybrid leaf trait values calculated from parent material are compared with data from putative hybrids and shown to be similar. The origin of these hybrids is discussed and shown to be the result of artificial sympatry resulting from indigenous, and recent exotic, domestication of the parent species. The hybrid is described asL. ×spontanea.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Colicin factors are thought to fall into two taxonomic groups which differ in, amongst other properties, the molecular weight of the plasmid DNA and the host range of the colicin protein. This hypothesis is supported by the plasmids found in 26 colicinogenic strains. Two small Col factors may have arisen from larger factors, judging from similarities between their colicins.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1617-4623
    Keywords: Haemolysin secretion ; HlyB ; ATP-binding motif
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hlyB secretion genes of Proteus vulgaris and Escherichia coli showed 81% nucleotide homology and similar E. coli-atypical codon usage. The deduced protein sequences differed in 54 of 707 residues and shared a previously unreported sequence which corresponds to the ATP-binding motif characteristic of protein kinases. The motif was also conserved in the HlyB of Morganella morganii. Of 4 oligonucleotide-directed substitutions introduced into the putative E. coli HlyB motif, 2 non-conservative changes caused radical reductions in the export of active haemolysin protein.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 151 (1977), S. 175-179 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A procedure is described for demonstrating plasmid DNA and its molecular weight, based on rate zonal centrifugation of unlabelled DNA in neutral sucrose gradients containing a low concentration of ethidium bromide. Each DNA species is then visualized as a discrete fluorescent band when the centrifuge tube is illuminated with ultra-violet light. Plasmids exist as closed circular and as relaxed circular molecules, which sediment separately, but during preparation of lysates, closed circular molecules are nicked so that each plasmid forms only a single band of relaxed circles within the gradient.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...