Prokaryotic Cells (prokaryotic + cell)

Distribution by Scientific Domains


Selected Abstracts


Grazing protozoa and magnetosome dissolution in magnetotactic bacteria

ENVIRONMENTAL MICROBIOLOGY, Issue 11 2007
Juliana L. Martins
Summary Magnetotactic bacteria show an ability to navigate along magnetic field lines because of magnetic particles called magnetosomes. All magnetotactic bacteria are unicellular except for the multicellular prokaryote (recently named ,Candidatus Magnetoglobus multicellularis'), which is formed by an orderly assemblage of 17,40 prokaryotic cells that swim as a unit. A ciliate was used in grazing experiments with the M. multicellularis to study the fate of the magnetosomes after ingestion by the protozoa. Ciliates ingested M. multicellularis, which were located in acid vacuoles as demonstrated by confocal laser scanning microscopy. Transmission electron microscopy and X-ray microanalysis of thin-sectioned ciliates showed the presence of M. multicellularis and magnetosomes inside vacuoles in different degrees of degradation. The magnetosomes are dissolved within the acidic vacuoles of the ciliate. Depending on the rate of M. multicellularis consumption by the ciliates the iron from the magnetosomes may be recycled to the environment in a more soluble form. [source]


Facets of heat shock protein 70 show immunotherapeutic potential

IMMUNOLOGY, Issue 1 2003
Stephen M. Todryk
Summary Amongst the families of intracellular molecules that chaperone and assist with the trafficking of other proteins, notably during conditions of cellular stress, heat shock protein (hsp) 70 is one of the most studied. Although its name suggests that expression is exclusively induced during cellular hyperthermia, members of the hsp70 family of proteins can be constitutively expressed and/or induced by a range of other cellular insults. The ubiquitous presence of hsp70 in eukaryotic and prokaryotic cells, combined with its high degree of sequence homology and intrinsic immunogenicity, have prompted the suggestion that inappropriate immune reactivity to hsp70 might lead to pro-inflammatory responses and the development of autoimmune disease. Indeed, hsp70 has been shown to be a potent activator of innate immunity and aberrant expression of hsp70 in certain organs promotes immunopathology. However, studies also suggest that hsp70 might have immunotherapeutic potential, as hsp70 purified from malignant and virally infected cells can transfer and deliver antigenic peptides to antigen-presenting cells to elicit peptide-specific immunity and, in contrast to its reported pro-inflammatory effects, the administration of recombinant hsp70 can attenuate experimental autoimmune disease. This review focuses on the immunoregulatory capacity of hsp70 and its potential therapeutic value. [source]


Antitumour activity and specificity as a function of substitutions in the lipophilic sector of helical lactoferrin-derived peptide

JOURNAL OF PEPTIDE SCIENCE, Issue 5 2003
Nannan Yang
Abstract A peptide L5 (PAWRKAFRWAWRMLKKAA), derived from the N -terminal ,-helical region of bovine lactoferrin (LFB 14,31), that is highly active against several tumour cell lines was reported earlier. In this study, a number of L5 analogues were designed in order to investigate how subsequent replacements of the aromatic amino acids in L5 with three amino acids representing different structural parameters influenced antitumour activity and tumour cell specificity relative to normal human cells. The Trp residues were substituted by Lys, Ile or Ala, while the Phe residue was substituted with Ala. The resulting peptides were investigated for their activity against prokaryotic cells, four tumour cell lines, human lung fibroblasts and human erythrocytes. Most of the peptides were highly active against both E. coli and S. aureus. The peptides were more active against the tumour cell lines than against normal eukaryotic cells but the activity against normal fibroblasts varied more among the peptides than did their antitumour activities. The results revealed that aromatic residues located opposite the cationic sector in L5 were more critical for antitumour activity than were aromatic residues located adjacent to the cationic sector. The biological responses for the peptides against tumour cell lines, fibroblasts, S. aureus (but not E. coli), were highly correlated with the amino acid descriptors used in our QSAR model. The result obtained from the QSAR study identified specific structural features that were important for lytic activity and membrane specificity. Certain structural properties in positions 3, 9 and 11 were shown to be important for antitumour activity, while additional structural properties in position 7 were found to be important with respect to tumour cell specificity. This information may offer a possibility for de novo design of an antitumour peptide with an improved therapeutic index. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd. [source]


Exploring prokaryotic diversity: there are other molecular worlds

MOLECULAR MICROBIOLOGY, Issue 1 2005
Luis Angel Fernández
Summary Prokaryotes are the major source of biological diversity on earth. This is not simply because of the large number of species present, or because of their diverse growth conditions and environmental niches populated by them, but because of the wealth of genes, metabolic pathways and molecular processes that are only found in prokaryotic cells. Therefore, Bacteria and Archaea (and their phages) cannot be considered any longer as miniaturized models of Eukaryotes, but as a genuine source of unique biological processes that are mediated by unique sets of genes and molecular devices. A true understanding of complex biological phenomena will require a deeper knowledge of this vast prokaryotic world. The second European Molecular Biology Organization (EMBO) conference on Molecular Microbiology entitled ,Exploring Prokaryotic Diversity' explored many aspects of this newly emerging interest in the prokaryotic world. [source]


Topological analysis of Hin-catalysed DNA recombination in vivo and in vitro

MOLECULAR MICROBIOLOGY, Issue 4 2004
Stacy K. Merickel
Summary In vitro studies have demonstrated that Hin-catalysed site-specific DNA inversion occurs within a tripartite invertasome complex assembled at a branch on a supercoiled DNA molecule. Multiple DNA exchanges within a recombination complex (processive recombination) have been found to occur with particular substrates or reaction conditions. To investigate the mechanistic properties of the Hin recombination reaction in vivo , we have analysed the topology of recombination products generated by Hin catalysis in growing cells. Recombination between wild-type recombination sites in vivo is primarily limited to one exchange. However, processive recombination leading to knotted DNA products is efficient on substrates containing recombination sites with non-identical core nucleotides. Multiple exchanges are limited by a short DNA segment between the Fis-bound enhancer and closest recombination site and by the strength of Fis,Hin interactions, implying that the enhancer normally remains associated with the recombining complex throughout a single exchange reaction, but that release of the enhancer leads to multiple exchanges. This work confirms salient mechanistic aspects of the reaction in vivo and provides strong evidence for the propensity of plectonemically branched DNA in prokaryotic cells. We also demonstrated that a single DNA exchange resulting in inversion in vitro is accompanied by a loss of four negative supercoils. [source]