Plasmids as Key Players in Adaptation.

This review briefly summarizes the data on the mechanisms of development of the adaptability of to various living conditions in the environment and in the clinic. A comparative analysis of the genomes of free-living and clinical strains of , as well as the genomes of and has been carried out. It has been shown that plasmids, both large and small, play a key role in the formation of the adaptability of to their living conditions. In particular, it has been demonstrated that the plasmids of various strains of differ from each other in their structure and gene composition depending on the lifestyle of their host bacteria. Plasmids of modern strains are enriched with antibiotic-resistant genes, while the content of genes involved in resistance to heavy metals and arsenic is comparable to plasmids from modern and ancient strains. It is concluded that plasmids may ensure the survival of host bacteria under conditions of various types of environmental and clinical stresses. A brief overview of the main mechanisms of horizontal gene transfer on plasmids inherent in strains is also given.