G-Quadruplex Structures in Bacteria: Functional Properties and Prospects for Use as Biotargets

G-quadruplexes (G4), non-canonical secondary DNA structures, have been intensively investigated for a long time. In eukaryotic organisms, they play an important role in the regulation of gene expression and DNA repair. G4 have also been found in the genomes of numerous bacteria and archaea, but their functional role has not yet been fully explored. Nevertheless, their participation in the formation of antigenic variability, pathogenicity, antibiotic resistance and survival in extreme conditions has been established. Currently, many tools have been developed to detect potential G4 sequences and confirm their formation ability. Since the controlled formation and resolution of the quadruplex is a significant instrument for regulation of the genes critical for survival, a promising direction is the search for ligands—the compounds that can have a stabilizing effect on the quadruplex structure and thereby alter gene expression. Currently, a number of ligands are already known to terminate the growth of pathogenic microorganisms. G4 ligands are of interest as potential antibiotics, which are extremely relevant due to the wide spreading of drug-resistant pathogens.