Bacteriophages current statement of the problem and its historical interpretations

Abstract

 Introduction.  Bacteriophages - viruses of bacteria, are relatively simple biological system and is a convenient model for studying basic problems virology, molecular biology and biotechnology. Significant success in learning mechanisms of nucleic acid replication, studies of fine structure genetic material, molecular mechanism of mutations, regulation protein synthesis and many other achievements of biology are connected with the application bacteriophages as convenient model objects. Phages, like all other viruses, are absolutely cellular parasites They carry information necessary for their own reproduction and at the same time, they do not have their own energy-synthesizing systems and protein-synthesizing mechanisms. Phages are the most numerous group of viruses on Earth. They can be found in all possible econiches occupied by their owners - bacteria. Bacterial viruses infect phytopathogenic bacteria, actinomycetes, blue-green algae, mycoplasmas.The genetic information of phages is encoded in its nucleic acid, the protein protects the genome from the action of external factors and performs a structural function, and also ensures the penetration of nucleic acid into a sensitive cell, is responsible for the antigenic and immunogenic properties of the virus. According to the above, the modern formulation of the problem of the use of bacteriophages in medical practice, the non-surface analysis of its historical roots seem timely. The purpose: is to perform an analysis of modern and retrospective (historical) data on the use of bacteriophages in the medical field (virology, in particular). Materials and methods.In order to objectify the informative annals and in-depth grounding of the work, we used the resources of retrospective analysis based on our own databases and previously accumulated thematic material. Prototypes were grounded using the resources of leading databases (Google, Yandex, etc.). Results& Discussion. Analysis of sources of scientific and practical and patent information showed that phages are more resistant to the action of physical and chemical environmental factors than many human viruses. Most of them are inactivated at a temperature above 65–70 °С, tolerate freezing well and are preserved for a long time at low temperatures and drying. Sulema, phenol do not have an inactivating effect on them. The resistance of bacteriophages to the effects of ionizing radiation and ultraviolet radiation has been revealed. Readers' attention is focused on the fact that the structure of bacteriophages was studied mostly on the example of phages of the T series of Escherichia coli. As a result, it was determined that the virus consists of an extended head containing DNA, a shell with a hollow core inside that resembles a stretched spring, and tail filaments. In addition, phages have a simpler structure - filamentous, in the form of crystals of icosahedral and octahedral forms. To date, there is no information on the mobility of bacteriophages. Literary sources testify in favor of the fact that the interaction of phages with the host cell begins as a result of an accidental encounter in the environment. It was also noted that the life cycle of bacteriophages that have entered the cell can take place in two ways that are significantly different from each other. Accordingly, virulent and lysogenic phages are distinguished. According to modern research, the development of virulent phages takes place in several stages.Phages are capable of species specificity. The specificity of the host and the phage is determined by the specificity of adsorption, which in turn depends on the receptors that are present in the cell wall of the host. According to the degree of specificity, polyphages are distinguished - capable of infecting several types of bacteria of the same genus, monophages - infecting bacteria of one species, typical phages - infecting only a certain strain (type) of bacteria of the same species.The second, third and fourth stages of development consist in the implementation of such processes as injection with the introduction of phage nucleic acid into the cell; suspension of the synthesis of DNA, RNA and proteins of the host cell (latent period) and synthesis of phage molecules from destroyed host DNA. This is what researchers call a complex multi-stage process (maturation of T-phages) when capsids with proteins are first formed, then after their dissolution, DNA appears and the capsids are blocked. The last stage consists in the release of phages under the influence of lysozyme through the destroyed cell wall of bacteria (bacteriolysis). The released phages begin to infect other host cells. Conclusion. A retrospective search on the subject of the development proved that the history of the study of phages, the mechanisms of their interaction with the bacterial cell (lysis and lysogeny) dates back to the second half of the 19th century and the 10th years of the 20th century, when in 1892 V. Kruse and S. Pansini, under the conditions of studying the growth of pneumococci spontaneous bacterial culture solution was described for the first time; bacteriologist M. Hankin (1896) obtained objective confirmation of the bactericidal effect of the water of the Jamna and Ganges on cholera vibrio, and in 1898 M. F. Gamaleya described the lysis (bacteriolysis) of bacteria (the causative agent of anthrax) under the influence of a transplanted agent. Events associated with the discovery of viruses parasitizing bacteria by the English microbiologist F. Twort (1915) and the French-Canadian researcher F. d'Herelle (1917); introduction of the term "bacteriophage" into scientific use; the selection from the biological samples of a dysentery patient of a filtering lytic agent capable of passages on the appropriate cultures of pathogens and dissolving their cells marked the completion of the initial historical stage of bacteriophage research.The scientific-theoretical search and study of the reference material conducted by the authors of the article demonstrated a rather narrow range of data on the respectively mastered prototypes (bacteriophage, specificity, absolute cell parasitism, bacteriophagy, modernity and history of the discovery and study of bacteriophages). Publications corresponding to the context of the topic mainly contain factual materials on the structure of bacteriophages, their specificities, life cycle, characterization data, virulent / lysogenic phages, information on issues of application in medical practice. Among the most elaborated directions, we note those where attempts to improve phage preparations are outlined in order to increase their effectiveness (constant replenishment with new highly active strains or races of phages obtained from various sources). Note that today there is a conscious scientific interest in issues related to the use of phages adapted to freshly isolated cultures of pathogens circulating at that time in a certain area. Taking into account the accumulated scientific, theoretical and practical experience, which confirms the obvious effectiveness of phages in the sense of application for the purpose of detecting bacteria (biological material samples, food products, raw materials), we emphasize the complete relevance and perspective of the vector of research chosen by the author's team.     

Keywords: bacteriophage, specificity, absolute cell parasitism, bacteriophagy, modernity and history of the issue.