Adaptive Modules in Permafrost Strains of and Their Distribution and Abundance Among Present Day Strains.

The /Xer system of site-specific recombination allows resolution of chromosomal dimers during bacterial DNA replication. Recently, it was also shown to be involved in horizontal transfer of a few known Xer-dependent mobile elements. Here, we show that plasmids of various species, including clinically important strains, often contain multiple p sites that are mainly located within their accessory regions. Chromosomes of strains may also contain additional sites, and their similarity with plasmid p sites is higher than with the main chromosomal site . We further identify putative mobile genetic elements containing p sites on both flanks of adaptive genes and analyze their distribution in species. In total, we describe seven mobile elements containing genes with various adaptive functions from permafrost strains of group. All of them are also spread in modern plasmids of different species including . We could not detect p sites and corresponding mobile elements in closely related bacterial genera, including and . Thus, the widespread distribution of modules is a characteristic feature of species and may contribute to their high adaptability both in the environment and in the clinic.