Comparative analysis of distribution of pseudogenes (YPO1582, YPO1728, YPO1967, and YPO4008) of strains of basic and supplementary species of the plague infection agent and pseudotuberculosis infection agent was performed. The genome of basic subspecies of plague infection agent species strain contains 3 different variants: intact genes, genes with IS-element inserts, or individual fragments. The pseudogene profile can be used as genetic marker of the Y. Pestis strains of basic subspecies from natural foci of plague. Strains of supplementary subspecies of Y. Pestis and Y. pseudotuberculosis contain these genes as the wild-type gene alleles. In addition to other factors, this fact can be regarded as evidence of ancient origin of plague infection agent supplementary subspecies and their similarity to pseudotuberculosis infection agent.