Autonomic (Mobile) Genetic Elements of Bacteria and Their Hierarchy

The following literature review is dedicated to autonomous genetic elements (AGE) of bacteria that are widespread in various genomes. AGE encode functions that are not essential for bacterium, but provide it with certain advantages (adaptation to new environmental conditions, "capture" and colonization of a new host etc.) and play an important role in ensuring the mobility of genomes. Current data on autonomous genetic elements of bacteria and features of their interaction has been summarized and analyzed in the article; mechanisms of autonomy of genetic elements and incompatibility of bacteriophages, plasmids and restriction-modification systems have also been considered. Classification and mechanisms of restriction-modification systems in bacterial cells have been regarded. Significant attention has been paid to the consideration of the incompatibility of autonomous genetic elements because it reflects their individuality and selfishness and even underlies the classification of some of them. Autonomous genetic elements are considered not only as prospective biotechnological objects for gene cloning and expression, but also as "tools" for research of many fundamental issues.