Mutational Variability of Yersinia pestis Under the Action of Phagocytising Cells of Rodents

The plague infection process involves interaction between Yersinia pestis and the rodent carrier’s phagocytes, contingent upon intracellular parasitism. The phagocytes’ oxygen-dependent cytocide system plays the pivotal antimicrobial role. Experimental simulation of natural variability using phagocytes in vitro and in vivo yields a broad range of Y. pestis mutants. Findings include mutagenic activity of phagocytes of Rhombomys opimus, Citellus pigmeus, white rats and activated phagocytes of guinea pigs. Mutants were obtained on auxotrophicity, virulence, with different levels of fraction I production and carbohydrate fermentation, with fibrinolytic and coagulase activity, missing from original strain. Deliverables include the Cyd– mutant, never isolated before. One-time action by phagocytes yielded Y. pestis mutants with double dependence on growth factors, induced by chemicals and physical factors only upon repetitive application. The results of Y. pestis natural mutagenesis modeling, taking onto account the peculiarities of pathogenesis, intracellular parasitism, the priority of the phagocytic immunity system, the mutagenic potential of phagocytes, the non-conjugativity of plasmids, the data on mutagenesis as the main mechanism of bacterial variability, and the lack of confirmed data on other natural factors of variability, allow us to postulate that variability under the action of phagocytes is the leading mechanism of variability in Y. pestis. in nature. Leading to population heterogeneity in the focus, Y. pestis mutational variability ensures selection and evolutionary variability associated with the main carrier species.