Bacteriophages Viruses

When a virus multiplies, the genome becomes released from the coat. This process occurs during the infection process. The present chapter is divided into three parts. The first part deals with basic concepts of virus structure and function. The second part deals with the nature and manner of multiplication of the bacterial viruses (bacteriophages). In this part we introduce the basic molecular biology of virus multiplication. The third part deals with important groups of animal viruses, with emphasis on molecular aspects of animal virus multiplication. 

Recently, it has been shown that photoactive fullerene derivatives (Cgo) were very effective in the photodynamic inactivation of bacterial viruses (bacteriophages). The treatment of water with CgQ-based PS under illumination resulted in a 2-log reduction in the number of bacteriophages in the water within only 2 min (Lee et ah, 2009). 

TABLE 24-1 The Sizes of DNA and Viral Particles for Some Bacterial Viruses (Bacteriophages)... 

Although spliceosomal introns appear to be limited to eukaryotes, the other intron classes are not. Genes with group I and II introns have now been found in both bacteria and bacterial viruses. Bacteriophage T4, for example, has several protein-encoding genes with group I introns. Introns appear to be more common in archae-bacteria than in eubacteria. 

Figure 5-13 Electron micrograph of a DNA molecule (from a bacterial virus bacteriophage T7) undergoing replication. The viral DNA is a long ( 14 pm) duplex rod containing about 40,000 base pairs. In this view of a replicating molecule an internal "eye" in which DNA has been duplicated is present. The DNA synthesis was initiated at a special site (origin) about 17% of the total length from one end of the duplex. The DNA was stained with uranyl acetate and viewed by dark field electron microscopy. Micrograph courtesy J. Wolfson and D. Dressier.

Examples of the products that can be obtained through the processes include DNA vectors, such as plasmids, viruses, bacteriophages and cosmids synthetic genes transformed human viruses (e.g. the Epstein-Barr virus) transformed bacterial cells containing specific properties animal and plant cells and bacteria mAbs, tissue cells regulatory proteins such as human insulin, interferons and human growth hormones and transgenic plants and animals. 

After years of work it has become possible to make the generalization that the nucleus of every cell invariably consists largely of nucleoproteins —compounds of nucleic acids and proteins. A few of the most important and interesting materials containing nucleoproteins are the chromosomes, the genes, and certain viruses, bacteriophages, and antigens. Yeast and... 

The progress made in cell culture techniques has provided a better understanding of viral replication cycles. Human viruses generally have a slow multiplication cycle requiring from 4 to more than 40 hours (in some herpesviruses) for completion this contrasts with bacterial viruses (bacteriophages) with a replication cycle as fast as 30 minutes. Certain viruses exhibit low infectivity for example, pi-cornavirus infectivity can be as low as 0.1% and rotavirus about 0.2%, and this makes the study of viral replication difficult. 

Bacteriophage Bacterial virus bacteriophage 1 is a biological reagent used in recombinant DNA cloning. 

EXAMPLE 8.17 Among the most important enzymes of recombinant DNA technology are the restriction enzymes. These are endonucleases that cleave DNA only at specific sequences of bases (called restriction sites). Typically, restriction sites are palindromic, in other words, the sequences are the same in the 5 — 3 and 3 — 5 strands. Restriction enzymes are produced by bacteria as an antiviral defense, and they cleave the DNA of viruses (bacteriophages) that infect them. However, they do not cleave host bacterial DNA. Fig. 8-17 shows the restriction sites of three common restriction enzymes, BamHI, EcoRI, and PvuII. Because BamHI and EcoRI cleave their restriction site asymmetrically, they produce overhangs in the cleaved DNA, called sticky ends. Conversely, PvuII cleaves symmetrically, producing blunt ends. 

Culture methods Culture methods are most widely employed to detect viruses in concentrates from water samples. Bacterial viruses (bacteriophages) are... 

Beyond the well-known base eomponents, several other bases and nucleosides occurring only in special nucleic acids have reeently been discovered. Some bacterial viruses (bacteriophages) contain in their nucleie acids the bases 6-hydroxymethylcytosine and S-hydroxymethyluracil. Soluble ribonucleic acid (i.e., transfer ribonucleic acid, see Section 6) contains pseudowridine, a 5-ribo-syluracil in which the sugar and the pyrimidine moieties are linked through a C—C bond. Transfer ribonucleie acid also contains a small proportion of methyl derivatives of the main nucleosides (especially N-methyl derivatives). 

Henry, M., Debarbieux, L., 2012. Tools from viruses bacteriophage successes and beyond. Virology 434, 151-161. 

Alfalfa mosaic virus Bacteriophage fd ( . coll) Bacteriophage R 17 ( . coli) Bacteriophage T 7 ( . coH) Bacteriophage T 2 (E. coli)... 

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