Ultrastructural Changes of Bacteria in Static Cultures of Yersinia pseudotuberculosis under Long Storage under Condition
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l Changes of Bacteria in Static Cultures of Yersinia pseudotuberculosis under Long Storage under Conditions of Low Temperature L. M. Somova, N. F. Timchenko, I. N. Lyapun, E. I. Drobot, E. V. Matosova, and M. P. Bynina
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 170, No. 8, pp. 192-195, August, 2020 Original article submitted May 18, 2020 Electron microscopy study revealed changes in the ultrastructure of bacteria of Yersinia pseudotuberculosis strains characterized by significantly reduced reproductive ability and virulence potential after long-term storage at low temperature of 4-8°C. Most bacterial cells contained dark cytosol with reduced cellular material or empty cytosol, while the cell wall was preserved. The revealed ultrastructural changes in the bacterial cells of the static culture of Y. pseudotuberculosis suggest that storage of strains under low positive temperatures could induce the transition of the majority of bacterial cell population to a dormant, non-cultivated state with a decrease in their virulence. This fact is of great scientific and applied importance in studies of causative agents of saprozoonoses, including pseudotuberculosis, which has the etiopathogenetic background of persistent infection. Key Words: Yersinia pseudotuberculosis; static culture; reduced virulence; ultrastructure; dormant state In all countries, irrespectively of the level of economic development, there is an increase in infectious pathology, which often has a latent, protracted, and chronic course [1]. Significant advances in molecular biology and genetics at the beginning of the XXI century expanded our understanding of the adaptive mechanisms of pathogens, their regulation, forms of existence, pathogenetic and epidemiological role in the infectious process [8,12,13]. One of the main causes of the development and spreading of chronic infections is the ability of pathogens to create stable (dormant) cell forms that do not always meet generally accepted taxonomic criteria for classifying bacteria. To a large extent, this was facilitated by the widespread use of antibacterial drugs, which significantly changed the clinical course of some infections. Such atypical cells are in a state of metabolic and reproductive rest, which makes them inaccessible for routine microbiological diagnostic
methods and insensitive to the action of most antibacterial agents [11,15]. In light of this, storage and further study of strains of pathogenic bacteria that caused chronically recurring infections is of great importance. A method of storage of microorganisms in semi-liquid agar under sterile mineral oil [2] makes it possible to maintain many types of bacteria for months or even years with reseeding 1-2 times a year on fresh medium. Inoculum tubes are stored in the refrigerator at 4-8°C. However, a decrease in virulence in museum strains of pathogenic microorganisms are sometimes observed in microbiological practice. Purpose of the study was to determine the ultrastructure of bacteria in Y. pseudotuberculosis s
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