36 The interaction of the virus with the cell. Reproduction of viruses.

The interaction is a common biological system at the genetic level.

There are four types of interaction:

1) a productive viral infection (interaction, which results in the reproduction of the virus and the cells die);

2) abortive viral infection (interaction, in which viral replication does not occur, and the cell restores the distributed function);

3) latent viral infection (the virus is a reproduction, and the cell retains its functional activity);

4) the virus-induced transformation (interaction, in which a cell that is infected with a virus, taking on new, previously inherent properties).

After the adsorption virions penetrate through endocytosis (viropeksisa) or as a result of the merger of viral and cellular membranes. Formed vacuoles containing whole virions or internal components fall into lysosomes where

deproteinization carried out, ie, the "stripping" of the virus, resulting in viral proteins are destroyed. The liberated nucleic acids from proteins by the virus enters the cell channel into the cell nucleus, or remain in the cytoplasm.

The nucleic acids of viruses implement a genetic program to create viral progeny and determine the genetic properties of viruses. With the help of special enzymes (polymerases) make copies of the parent nucleic kitty items (replication occurs), and synthesized messenger RNAs that bind to ribosomes and synthesize viral proteins subsidiaries (translation).

Once in the infected cell accumulates enough components of the virus, begins assembling progeny virions. This process usually takes place near the cell membrane, which sometimes take a direct part in it. As part of the newly formed virions are frequently found substances characteristic of the cells in which the virus multiplies. In such cases, the final step of forming virions is blocked enveloping layer of the cell membrane.

The last stage of the interaction of viruses with cells is the way out of the cell or release of daughter viral particles. Simple viruses lacking superkapsid cause degradation of the cells and fall into the intercellular space.

Other viruses that have a lipoprotein envelope out of the cells by budding. In this case, the cell remains viable for a long time. In some cases, viruses accumulate in the cytoplasm or the nucleus of infected cells, forming a crystal-like clusters - inclusion bodies.

37. Bacteriophages. Types of morphology. The chemical composition.

Bacteriophages (from 'bacteria' and Greek. Phagos - eater) - Viruses

of bacteria having the ability to specifically penetrate bacterial cells reproduce them and cause their dissolution (lysis).

Bacteriophages are widely distributed in nature. They are found in water, soil, food products, various secretions of humans and animals, is, where there are bacteria. At present, these viruses were detected in the majority bacteria disease-causing as well as no disease, as well as a number of other organisms (eg fungi). Therefore, in the broadest sense of the word, they were called simply phages. Phages vary in shape, structural organization, type and nature of the nucleic acid interactions with microbial cell.

Morphology. Most phages under the electron microscope, have the shape of a tadpole or sperm, some - cubic or filamentous form. Dimensions phages range from 20 to 800 nm in filamentous phages. The best studied large bacteriophages shaped sperm. They consist of an elongated icosahedral head size 65 -100 nm and tail ridge longer than 100 nm. Inside the caudal ridge has a hollow shaft in communication opening the head outside Sheath capable of reducing such as muscle. The caudal ridge ends hexagonal basal plate with short spines, which depart from the filamentous structure - the fibrils

There are also phages having the long arm, Case is not able to contract, phages with short processes, analogous processes, no process. The chemical composition. Phages are composed of two major chemical components - a nucleic acid (DNA or RNA) and proteins. In phage-shaped sperm double-stranded DNA is densely packed in a spiral inside the head. Proteins included in the shell (capsid) surrounding the nucleic acid and all the structural elements of the tail bone. Phage structural proteins differ in composition polypeptides and represented a plurality of identical subunits arranged along a spiral type or cubic symmetry. In structural proteins, some phages detected internal (genomic) proteins associated with the nucleic acid and enzyme proteins involved in the interaction of the phage to the cell.

Resistance. Phages are more resistant to chemical and physical factors than bacteria. A number of disinfectants (phenol, ethanol, ether and chloroform) have no significant effect on the phages. Phages are highly sensitive to formalin and acids.

Inactivation of most phages occurs at a temperature of 65 - 70 ° C. For a long time, they are saved by drying in sealed ampoules, freeze at a temperature of -185 ° C in glycerol.