[The range of pathogen variation due to discussion of different hypotheses of plaque].

The paper reviews the hypotheses that explain the mechanism of plague enzooty in natural foci, which are based on a concept of a wide range of plague microbial variability. A comparative analysis of the parameters of variability in the experimentally obtained plague microbial strains and "atypical" natural isolates of the causative agent has led to the conclusion that the mechanism of adaptive variability is due to a phenotypic change in ontogenesis that reflects the philogenetic pathway of the adaptability of a plague microbe to constantly changing living conditions in the ecological niche assimilated by the causative agent.