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1

Plasmids of lactic acid bacteria

100%
Walczak P.
Biotechnologia
|
2005
|
issue 3
144-164
EN
The role and significance of natural plasmids existing in lactic acid bacteria (LAB) from genus Lactococcus, Lactobacillus and Leuconostoc in their metabolic diversity and industrially important properties have been described. Molecular organization of plasmids, their mechanisms of replication and metabolic activity were discussed in detail with particular stress put on their common features such as structure similarity, segregational and structural stability, biochemical traits and the presence of insertion sequences. The role of plasmid borne IS elements on plasmid stability and adaptative properties of LAB were also discussed.
2

DNA vaccines: are they still just a powerful tool for the future?

100%
Belakova J., Horynova M., Krupka M., Weigl E., Raska M.
Archivum Immunologiae et Therapiae Experimentalis
|
2007
|
vol. 55
|
issue 6
387-398
EN
Vaccination is historically one of the most successful strategies for the prevention of infectious diseases. For safety reasons, modern vaccinology tends toward the usage of inactivated or attenuated microorganisms and uses predominantly subunit vaccines. The antigens need to be clearly defined, pure, stable, appropriately composed, and properly presented to the immune system of the host. Differing ratios of various proportions between specific CD4+ and CD8+ T cell responses are essential for conferring the required protection in the case of individual vaccines. To stimulate both CD4+ and CD8+ T cells, the antigens must be processed and presented to both antigen-presentation pathways, MHC I and MHC II. Protein antigens delivered by vaccination are processed as extracellular antigens. However, extracellularly delivered antigen can be directed towards intracellular presentation pathways in conjugation with molecules involved in antigen cross-presentation, e.g. heat shock proteins, or by genomic-DNA vaccination. In this overview, current knowledge of the host immune response to DNA vaccines is summarized in the introduction. The subsequent sections discuss techniques for enhancing DNA vaccine efficacy, such as DNA delivery to specific tissues, delivery of DNA to the cell cytoplasm or nucleus, and enhancement of the immune response using molecular adjuvants. Finally, the prospects of DNA vaccination and ongoing clinical trials with various DNA vaccines are discussed.
3

Plasmids R577 and R785 decrease the resistance of Escherichia coli K12 strain W1485 to bactericidal action of normal serum

80%
Jankowski S., Cisowska A.
Journal of Applied Genetics
|
1998
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vol. 39
|
issue 3
211-216
EN
The role of plasmids of drug resistance R577 and R785 in the development of susceptibility of Escherichia coli K12 strain W1485 to the bactericidal action of serum was studied. Plasmids R577 and R785 were transfered to cells of strain W1485 by means of conjugation. The susceptibility of cells containing the plasmid to serum was compared to that of cells lacking the plasmid. It was found that plasmids R577 and R758 sensitize bacteria to the action of serum.
4

The minimal genome paradox

70%
Wegrzyn G.
Journal of Applied Genetics
|
2001
|
vol. 42
|
issue 3
385-392
EN
The concept of a ?minimal genome? has appeared as an attempt to answer the question what the minimum number of genes or minimum amount of DNA to support life is. Since bacteria are cells bearing the smallest genomes, it has been generally accepted that the minimal genome must belong to a bacterial species. Currently the most popular chromosome in studies on a minimal genome belongs to Mycoplasma genitalium, a parasite bacterium whose total genetic material is as small as 580 kb. However, the problem is how we define life, and thus also a minimal genome. M. genitalium is a parasite and requires substances provided by its host. Therefore, if a genome of a parasite can be considered as a minimal genome, why not to consider genomes of bacteriophages? Going further, bacterial plasmids could be considered as minimal genomes. The smallest known DNA region playing the function of the origin of replication, which is sufficient for plasmid survival in natural habitats, is as short as 32 base pairs. However, such a small DNA molecule could not form a circular form and be replicated by cellular enzymes. These facts may lead to an ostensibly paradoxical conclusion that the size of a minimal genome is restricted by the physical size of a DNA molecule able to replicate rather, than by the amount of genetic information.
5

DNA libraries ? a way to understand genome structure

70%
Wolko L., Slomski R.
Biotechnologia
|
2003
|
issue 3
159-179
EN
Wide genome physical mapping is becoming a main goal of current genomic research on many plant and animal species. It provides essential basis for large-scale genome sequencing, but requires well-saturated large-insert DNA genomic libraries. This review presents a progress in the construction and application of genomic libraries. New trends towards the improvement of cloning vectors and adjustment to new tasks of molecular genetics are also presented.
6

Is tRNA only a translation factor or also a regulator of other processes?

70%
Wegrzyn G., Wegrzyn A.
Journal of Applied Genetics
|
2008
|
vol. 49
|
issue 1
115-122
EN
Abstract. tRNA has been discovered as a factor playing a central role in the translation of genetic information (encoded in DNA and transcribed to mRNA) into amino acid sequences of proteins. However, subsequent studies led to the hypothesis that during evolution, tRNA originated in replication, not translation. Indeed, there are many examples of tRNA-like molecules playing roles in reactions other than translation, including replication of various replicons. In this review, we have focused on functions of tRNA molecules (not tRNA-like structures) outside of their direct roles in translation as factors for a passive transportation of amino acids into a ribosome and deciphering triplets of nucleotides in codons of mRNA. Interestingly, it appears that such tRNA-dependent reactions are effective only when tRNA is uncharged. The most spectacular examples come from bacterial cells and include induction of the stringent control, regulation of transcription of some operons, and control of replication of ColE1-type plasmids. Recent studies indicated that tRNA (not only pre-tRNA, shown previously to be capable of self-excision of intron sequences) can be responsible for specific cleavage of another transcript, a ColE1 plasmid-encoded RNA I, which is involved in the regulation of plasmid DNA replication initiation. If this reaction is not restricted to RNA I but represents a more general phenomenon, one might suspect a potential role for uncharged tRNA molecules in regulation of various processes, whose efficiency depends on tRNA-cleavable RNAs. This kind of regulation would provide a possibility for a cell to respond to different nutrition conditions resulting in different levels of tRNA aminoacylation.
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