Bacillus anthracis, the causative agent of anthrax, has two virulence plasmids: pXO1 and pXO2. Plasmid pXO2 carries the genes of an antiphagocytic capsule synthesis. Plasmid pXO1 carries the genes pagA, lef, and cya encoding anthrax toxins, as well as atxA, which encodes the main regulator of pathogenicity factor expression. In the present paper, we evaluated the polymorphism of the pagA, lef, cya, and atxA genes for 85 B. anthracis strains belonging to different evolutionary lineages and canSNP groups and three B. cereus strains possessing pXO1-like plasmids. We found 19 genotypes (GT) strongly correlated with the main evolutionary lineages; they were mainly correlated with the canSNP group within these lines. In some cases, one GT combined the strains of several canSNP groups, and some canSNP groups were divided into several GTs. The most interesting of such cases were 1) the formation of a separate GT by strains of the A.Br.008/009 group isolated in the former USSR; 2) the presence of a unique GT in some American strains of the A.Br.Aust94 group; 3) the division of the A.Br.001/002 group into two subgroups, one of which may be a transitional link to the group A.Br.Ames; 4) the fact that European isolates of the B.Br.CNEVA group and Arctic strains of the B.Br.001/002 group have a common GT.

Tularemia is a severe infectious disease caused by the Gram-negative bacteria Francisella tularensis. F. tularensis is currently divided into three subspecies, holarctica, tularensis and mediasiatica which differ in their virulence and geographic distribution. Subspecies mediasiatica is the least studied because of its very low documented virulence for humans and limited geographic distribution. It was discovered in sparsely populated regions of Central Asia. Since 2011, a new subsp. mediasiatica lineage was identified in Altai (Russia). In 2021, we isolated one subsp. mediasiatica strain in Krasnoyarsk Territory. In spite of its geographic origin, 500 km east from Altai, this strain belongs to the Altai lineage and contributes surprisingly little genetic diversity to previous knowledge. This improved knowledge of the phylogeography of subsp. mediasiatica led us to propose a scenario in which the two zoonotic lineages, holarctica and tularensis, independently emerged from the mediasiatica lineage in Siberia or Central Asia, and make predictions which will allow to challenge this hypothesis