[Repeats in bacterial genomes: evolutionary considerations]

Contemporary data on repeated nucleotide sequences (repeats) in bacterial genomes are discussed. Different classifications and distribution of the repeats in the genomes of bacteria belonging to different species are reviewed. Comparative data on the density of repeats in the genomes of pathogenic and non-pathogenic bacteria, as well as in the genes encoding different functions of microbial cell (genes of stress response, genes controlling DNA metabolism and repair, etc.), are discussed. The role of the repeats in the uptake and loss of genetic material by bacterial genomes is discussed. It is suggested that repeats are responsible not only for the functioning of bacterial genome at the given moment of time, but also for the structures of the implicit genomes, which may appear in the future due to evolutionary significant genomic rearrangements.